Extended Reality Guidelines for Supporting Autism Interventions Based on Stakeholders' Needs

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Introduction

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition with a worldwide prevalence of around one percent [START_REF] Lord | Autism spectrum disorder[END_REF], and three main features (American Psychiatric Association, 2013): social communication and social interaction disorders, focused interests, and sensory modulation disorders. In particular, sensory disorders affect around 90% of autistic people1 over the different sensory channels [START_REF] Robertson | Sensory perception in autism[END_REF]. Autistic traits include a tendency to focus on the details rather than on the overall situation [START_REF] Frith | Autism: explaining the enigma[END_REF], a perception that the world is going too fast [START_REF] Gepner | Ralentir le monde pour mieux le percevoir : un nouveau traitement pour les enfants autistes ?[END_REF], executive dysfunction with for instance a resistance to change [START_REF] Lord | Autism spectrum disorder[END_REF], and an associative thinking requiring to compare past experiences in order to make sense of a situation [START_REF] Grandin | How does visual thinking work in the mind of a person with autism? A personal account[END_REF]. Co-occurring conditions are also common, e.g, attention disorders [START_REF] Lord | Autism spectrum disorder[END_REF]. Since autistic people belong to a spectrum, they display various sensorimotor and cognitive abilities, some requiring substantial support, being non-verbal and with cognitive disabilities, while others require "minimal support to complete academic work" (Bottema-Beutel et al. 2021, p.3).

While early, structured, and individualized approaches are advised to address autism challenges, multiple interventions exist [START_REF] Sandbank | Project AIM: Autism intervention meta-analysis for studies of young children[END_REF]. Behavioral interventions, such as Applied-Behavioral Analysis (ABA), focus on the child's behavior, including its antecedents and consequences, with many strategies, e.g., reinforcements [START_REF] Lovaas | Behavioral treatment and normal educational and intellectual functioning in young autistic children[END_REF]. They can be combined with alternative communication methods, e.g., the Picture Exchange Communication System (PECS) [START_REF] Flippin | Effectiveness of the Picture Exchange Communication System (PECS) on Communication and Speech for Children With Autism Spectrum Disorders: A Meta-Analysis[END_REF], or Makaton [START_REF] Montoya | Le programme Makaton auprès d'un enfant porteur d'autisme : le cas de Julien[END_REF].

Developmental interventions are grounded in developmental psychology and focus on active exploration and child-practitioner interactions [START_REF] Piaget | The Psychology of the child (Nachdr.)[END_REF]. Naturalistic Developmental Behavioral Interventions (NDBI) draw upon both previous interventions to teach developmental skills within naturalistic settings [START_REF] Schreibman | Naturalistic Developmental Behavioral Interventions: Empirically Validated Treatments for Autism Spectrum Disorder[END_REF], e.g., the Early Start Denver Model (ESDM) [START_REF] Rogers | Effects of a Brief Early Start Denver Model (ESDM)-Based Parent Intervention on Toddlers at Risk for Autism Spectrum Disorders: A Randomized Controlled Trial[END_REF]. Other interventions mainly focus on structuring the environment and self-monitoring, e.g., Treatment and Education of Autistic and related Communication-handicapped CHildren (TEACCH) [START_REF] Mesibov | The TEACCH approach to autism spectrum disorders[END_REF]. Psychodynamic interventions then focus on the social interactions and how thoughts affect behavior [START_REF] Midgley | The Evidence-Base for Psychodynamic Psychotherapy With Children and Adolescents: A Narrative Synthesis[END_REF]. Sensory-based interventions also exist, to enhance the integration of multisensory interactive processes and cognitive abilities, such as with Sensory Integration Therapy [START_REF] Schoen | A Systematic Review of Ayres Sensory Integration Intervention for Children with Autism[END_REF], or to prompt child-practitioner interactions through multisensory spaces, such as with Snoezelen [START_REF] Lancioni | Snoezelen: an overview of research with people with developmental disabilities and dementia[END_REF]. At last, integrative interventions use elements from different interventions to best suit the child's needs [START_REF] Klein | Integrative Approaches to Caring for Children with Autism[END_REF]). Yet, interventions often present challenges, such as difficulties in terms of access, flexibility, hard-to-get training, or expensive cost [START_REF] Griffith | I just don't fit anywhere': support experiences and future support needs of individuals with Asperger syndrome in middle adulthood[END_REF][START_REF] Lang | Review of Teacher Involvement in the Applied Intervention Research for Children with Autism Spectrum Disorders[END_REF]. This paper suggests using technology-based interventions to support them.

Technology-based interventions using video games on various mediums such as tablets, desktop computers, or robots, are promising to overcome these issues, as they often appeal to autistic children [START_REF] Grynszpan | Innovative technology-based interventions for autism spectrum disorders: A meta-analysis[END_REF][START_REF] Mazurek | Video games from the perspective of adults with autism spectrum disorder[END_REF]. More specifically, recent reviews highlight that Virtual Reality (VR) [START_REF] Bradley | Autism and virtual reality head-mounted displays: a state of the art systematic review[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF][START_REF] Parsons | State-of-the-art of virtual reality technologies for children on the autism spectrum[END_REF][START_REF] Parsons | Virtual Reality in Pediatric Psychology[END_REF] and Augmented Reality (AR) [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Khowaja | Augmented Reality for Learning of Children and Adolescents With Autism Spectrum Disorder (ASD): A Systematic Review[END_REF][START_REF] Marto | Using Augmented Reality in Patients with Autism: A Systematic Review[END_REF] are promising to complement autism interventions, through the creation of secure and individualized spaces, with a precise control over different stimuli, and the possibility to rehearse and record actions. Moreover, they display a good acceptability and usability with Head-Mounted Displays (HMDs) [START_REF] Malihi | Short report: Evaluating the safety and usability of head-mounted virtual reality compared to monitor-displayed video for children with autism spectrum disorder[END_REF][START_REF] Newbutt | Using Virtual Reality Head-Mounted Displays in Schools with Autistic Children: Views, Experiences, and Future Directions[END_REF] and room-centric spaces, e.g., Cave Automatic Virtual Environments (CAVE) [START_REF] Cruz-Neira | The CAVE: audio visual experience automatic virtual environment[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF]. In this paper, VR and AR are referred under the term Extended Reality (XR), because what belongs to the real and virtual worlds is a matter of proportions according to the virtuality continuum [START_REF] Milgram | A Taxonomy of Mixed Reality Visual Displays[END_REF]. Contrary to low-immersive devices (e.g., desktop computers), XR technology offers embodied multisensory capabilities which can be highly engaging for autistic individuals [START_REF] Miller | Level of Immersion in Virtual Environments Impacts the Ability to Assess and Teach Social Skills in Autism Spectrum Disorder[END_REF].

Although previous XR design reviews were conducted about autism interventions [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF], or more specifically NDBI [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], they seem to be disconnected from field practices that stakeholders encounter or use on a daily basis. Indeed, they are not informed by stakeholders' views, namely, the views from practitioners and autistic individuals. Hence, this paper aims at extending these previous reviews by adopting a participative design perspective mainly accounting for practitioners' views. So far, most XR studies focus on socio-emotional abilities, as revealed by two systematic reviews [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF]. Indeed, even when some studies mention using XR as Assistive Technologies for autism interventions [START_REF] Rosenfield | A Virtual Reality System for Practicing Conversation Skills for Children with Autism[END_REF][START_REF] Syriopoulou-Delli | Applications of assistive technology in skills development for people with Autism Spectrum Disorder: a systematic review[END_REF], they concern the training of socio-emotional abilities, and not XR technologies that could be added to support and enhance the daily life of autistic people. Thus, most studies exclude the individuals who cannot work on such skills, because these individuals already require substantial support for conducting daily tasks [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]). Yet, Parsons et al. (2019)'s findings from a two-year seminar including 240 stakeholders indicated that perceptual specificities have to be more considered during the design process to better support autism interventions. This involves using participative design to give all stakeholders a voice [START_REF] Fletcher-Watson | Making the future together: Shaping autism research through meaningful participation[END_REF][START_REF] Frauenberger | Designing technology for children with special needs: bridging perspectives through participatory design[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Porayska-Pomsta | Developing technology for autism: an interdisciplinary approach[END_REF]. By using such a participative design approach and considering all stakeholders' concerns, this study aims at suggesting XR use cases to complement common interventions.

Moreover, most XR studies display inherent biases, due to possible misunderstandings or anxiety from autistic users, which prevent from their full validation [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]. They often come from a lack of communication between the different stakeholders involved (i.e., academics, practitioners, autistic individuals) [START_REF] Pellicano | A Future Made Together: shaping Autism Research in the UK[END_REF][START_REF] Pellicano | What should autism research focus upon? Community views and priorities from the United Kingdom[END_REF], or from a non-consideration of autistic perception, non-ecological tests, or noncollaborative designs [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]). Yet, apart from the recent Dechsling et al. [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF].

Third, autism XR design guidelines are drawn from a comparison between the interviews' findings, and the findings from a literature survey that we conducted. After detailing the methods, results are presented following these three contributions. A discussion finally suggests future directions for the XR autism research field.

Methods

The first objective of this paper was to get insights about common autism interventions, to then derive XR use cases and guidelines that are close to stakeholders' needs. To that respect, semi-directed interviews were designed and conducted, following methods that are described in the next subsection. The second objective was to check whether stakeholders' insights about potential XR uses as a support for interventions, that were collected during the interviews, matched the focus of the existing XR studies. As two recent systematic literature reviews focusing on XR autism interventions existed at the time of our study [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF], the interviews' findings were compared with the findings from these reviews. At last, this paper aimed at offering XR design guidelines drawing upon stakeholders' needs, as such guidelines were not provided by the two previous systematic reviews, nor by other reviews specifically focusing on XR autism design guidelines [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]. Thus, an XR literature design survey was conducted to look for these guidelines, and the interviews' findings were then compared with the survey's findings. The method used to conduct this survey is presented in the second subsection called "Method for the literature survey".

Method for the semi-directed interviews

Semi-directed interviews were conducted with French autism stakeholders, mainly including practitioners. After presenting the methodology, data analyses are exposed, both being summarized in Figure 1. [Figure 1 top]

Participants

To get in contact with autism stakeholders, personalized emails were sent to three Autism Resource Centers, 49 healthcare structures specialized in autism and neurodevelopmental disorders, three associations representing autistic individuals and relatives, and 66 practitioners. Most contacts were found in the TAMIS address list 2 . Moreover, proceedings of recent conferences about autism, sensoriality and technology were identified, using queries with the following keywords: "ASD" OR "autism", "digital" OR "technology", and "sensoriality". In Europe, sixteen conferences or workshops appeared, from 2012 to 2019, mainly in France, except for two in Spain and one in England. Every attendee's profile was examined and contacted when their activity simultaneously focused on autism, technology, and sensoriality. Furthermore, people interviewed were asked for other contacts at the end of each interview. Other experts were discovered through papers, blogs, and Autism Resource Centers' webpages. Only French participants were contacted to avoid language misunderstanding with the main author.

Moreover, most participants were in the Ile de France area (i.e., Paris district), to facilitate further in-situ investigations, e.g., observations of medical practice.

Formal interviews were conducted with 34 stakeholders, including practitioners (n=29), people from the autism community (n=4), and academics (n=1). Table 1 summarizes their profiles, which tend to be representative of the distribution of all autism fields [Table 1]. Practitioners and academics are highly experienced, often with more 2 The Tamis list details practitioners and associations specialized on autism in Ile de France -tamis-autisme.org/) than ten years of practice (n=21). Practitioners have various backgrounds, i.e., public sector (n=10), private sector (n=5), or both (n=14). They mainly use NDBI (n=9), integrative (n=8), and sensory-based (n=7) interventions.

Autistic individuals and their relatives favored NDBI (n=4), and often mentioned the ABA method. Technologybased interventions were often reported (n=23), and all autistic participants already used digital tools (n=4). All participants agreed to be contacted again for further questioning or future testing.

Protocol

Interviews had two objectives: first getting an overview of how autism interventions are conducted, and second gathering the potential needs and viewpoints of participants regarding the use of digital tools as a support for interventions, and particularly XR. Interviews were based on a semi-directed questionnaire targeting practitioners that was built in three phases as suggested by [START_REF] Lallemand | Méthodes de design UX: 30 méthodes fondamentales pour concevoir et évaluer les systèmes interactifs[END_REF]: phase 1 -demographics (2 questions); phase 2 -interview body (30mn, 9 questions); and phase 3ending (5mn -2 questions). The interview body is divided into two main parts targeting common autism interventions without digital tools from questions 3 to 9 (Q3 to Q9), and then with digital tools from Q10 to Q11. About the first part, Q3 to Q7 covered the main aspects of non-digital autism interventions. These questions were derived from the authors' knowledge at the beginning of the study, coming from a non-exhaustive review of the literature, including the French grey literature about intervention guidelines (Haute Autorité de Santé, 2018), as well as online communications from Autism Resource Centers. Then, Q8 targeted sensory-based interventions, to assess their relative importance among common practices. Q9 was added after the sixth interview, as all participants mentioned the use of mediation activities.

Then, the second part investigated the current use and potential needs regarding digital tools (Q10) and XR (Q11).

All questions were rephrased depending on the participant and on the context of the interview. Table 2 presents the basis of the questions in column 2, with respect to the three interview phases in column 1 [Table 2]. For each question, keywords being representative of related topics were used to ask for additional details when these topics were not spontaneously mentioned by the interviewee. The list of keywords was gradually extended and refined over time, as the authors gained insights about autism interventions, the final list being displayed in column 3. To elicit more insights over specific actions and practices, the critical incident technique [START_REF] Flanagan | The Critical Incident Technique[END_REF] was used, i.e., participants were always asked to give precise examples of the elements they were speaking about, for instance by describing the last time when the element occurred. With autistic participants, non-appropriate question was removed (Q3), and two questions were added: QA1 assessed their viewpoints regarding the healthcare interventions that they experienced, and QA2 asked about their atypical sensory perception. With academic participants Q3 was removed, and technology-focused questions were more explored (Q10, Q11).

Interviews with autism experts last between 34' and 94' with a mean duration of 59'. They include 19 women and 11 men, and were conducted using phone (n=18), visio-conference (n=7), or face-to-face (n=5). With autistic individuals and/or their families, they last between 43' and 70', with a mean duration of 51', and were conducted using phone (n=3), or face-to-face (n=1). Two interviews were conducted with mothers of autistic children (one boy and one girl), one interview with an autistic man, and one interview with an autistic man and his family (the family being present due to his specific needs). Every participant signed a consent form prior interview, mentioning they were free to stop whenever they wanted. All interviews were audio recorded. All data collected were anonymized for transcription and analysis, using the "itw" keyword followed by the interview number. For security reasons, no online cloud system was used to store data, and transcriptions were made manually.

Data analysis

Data analysis mainly used a bottom-up approach with inductive coding called grounded theory [START_REF] Charmaz | Constructing grounded theory: a practical guide through qualitative analysis[END_REF].

Hence, interview data was coded to extract meaningful phrasings, that were then sorted into different concepts and categories. The technique starts from no preconceived concepts. Instead, they are gradually built through multiple iterations between the data, concepts, and categories, which involves the use of constant comparative methods at the different analytic stages (Charmaz, 2006, p.54). The analysis process stops when the classification becomes stable. As concepts are sometimes connected, the same phrasing can be sorted into multiple concepts. During this qualitative analysis process, the first author' subjectivity could have influenced the findings. Thus, to limit potential biases, an objectivist approach was used, i.e., the analysis focused on the interview data for themselves, without considering how they were produced (Charmaz, 2006, p. 131). Hence, repetitions, hesitations, and prosody were not considered during the transcription process. This overall grounded theory analysis includes three main steps. First, four main grounded theory iterations were conducted by the first author at different times (i.e., offset of several weeks) to reduce potential biases. Since all interviews were conducted in French, the concepts and categories were first created in French, and then translated and refined in English. To analyze interview data about non-digital interventions, only inductive coding was used.

About data regarding digital tools and XR, inductive coding was first used, and then, from a late analytic stage, the emerging concepts were refined in connection with the XR autism literature to reveal potential gaps [START_REF] Charmaz | Constructing grounded theory: a practical guide through qualitative analysis[END_REF]. This comparison process started at a late analytic stage to avoid importing too many pre-conceived ideas when starting the analysis. It involved the second and third steps of our overall analysis process. In the second step, participants' needs regarding XR uses were compared with the existing XR uses that were reported by two systematic reviews [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF] (see results' section called "Comparison between stakeholders' needs and literature XR uses"). These reviews were selected as they were recent, systematic, and exhaustive regarding XR existing use cases, and thus allowed to derive objective percentages representing the relative significance of the different purposes of XR autism studies (e.g., social training). Thus, they were suitable to draw a comparison with our interviews' findings, and to reveal potential gaps. At last, during a third analytic step, since the two systematic reviews did not provide XR design guidelines accounting for stakeholders' needs, nor other reviews specifically focusing on XR autism design guidelines [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], an XR autism literature survey was conducted in relation to our emerging grounded theory. The objective was to identify such guidelines that we could then compare with the interviews' findings (see results' section "Comparison between stakeholders' XR design insights and literature guidelines"). The method that was used to conduct this literature survey is described hereafter. The three overall analytic steps were here presented sequentially for enhanced clarity, but they were conducted in parallel during the late analytic stage.

Method for the literature survey

Method for the article selection from the literature

Drawing from Charmaz (2006, p.164-168)'s grounded theory method, we conducted an XR autism literature survey during the late analytic stage. The purpose was to derive literature design guidelines that we could compare with the interviews' findings. At this late analytic stage, major XR concepts about sensorimotor and mediation issues had emerged that were not expected when conducting the interviews. Hence, as the survey was informed by the state of the grounded theory, it focused more on XR sensorimotor and mediation issues. Moreover, the survey mainly considered participative design approaches to consider all stakeholders' views. Online queries were made with Google Scholar engine, to use the "cited by" option for each paper and thus reference more recent studies with similar interests. They combined the keywords: "Autism" OR "ASD", "Virtual Reality" OR "Virtual Environment" OR "Augmented Reality" OR "Mixed Reality" OR "Technology" OR "Digital Tool", "Multisensory Environment" OR "Sensoriality" OR "Mediation", and "Participative Design".

Two inclusion/exclusion criteria were used: (1) autism-related stereoscopic XR studies were included (e.g., CAVE and HMDs), or computer-related studies, if presenting relevant features for the XR medium (i.e., robot, touchscreen device, or room-centric setup); and (2) articles not offering design guidelines were excluded. Moreover, we focused more on participative design studies, as being more representative of all stakeholders' views.

Screening process and protocol for analysis

The first author searched the literature and reviewed all the studies according to the inclusion/exclusion criterions.

The title was first screened. If relevant, the abstract was then screened, and followed by a full-text reading. If relevant, the study was then included in the survey. In total, 37 articles were selected [START_REF] Alcorn | Motivating children's initiations with novelty and surprise: initial design recommendations for autism[END_REF][START_REF] Aruanno | HoloLearn: Wearable Mixed Reality for People with Neurodevelopmental Disorders (NDD)[END_REF][START_REF] Bartoli | Designing and evaluating touchless playful interaction for ASD children[END_REF][START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Brosnan | Look up! Digital technologies for autistic people to support interaction and embodiment in the real world[END_REF][START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Constantin | Designing computer-based rewards with and for children with Autism Spectrum Disorder and/or Intellectual Disability[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Duris | Le robot Nao comme support relationnel et de dynamique groupale auprès d'enfants porteurs de troubles du spectre autistique[END_REF][START_REF] Garzotto | Wearable Immersive Virtual Reality for Children with Disability: a Case Study[END_REF][START_REF] Garzotto | Magic Room: A Smart Space for Children with Neurodevelopmental Disorder[END_REF][START_REF] Halabi | Design of Immersive Virtual Reality System to Improve Communication Skills in Individuals with Autism[END_REF][START_REF] Kerns | Attention and working memory training: A feasibility study in children with neurodevelopmental disorders[END_REF][START_REF] Koirala | An Exploration of Using Virtual Reality to Assess the Sensory Abnormalities in Children with Autism Spectrum Disorder[END_REF][START_REF] Krishnappa Babu | Gaze-Sensitive Virtual Reality Based Social Communication Platform for Individuals with Autism[END_REF][START_REF] Kuriakose | Design of a Physiology-Sensitive VR-Based Social Communication Platform for Children With Autism[END_REF][START_REF] Lorenzo | The application of immersive virtual reality for students with ASD: A review between 1990-2017[END_REF][START_REF] Malihi | Short report: Evaluating the safety and usability of head-mounted virtual reality compared to monitor-displayed video for children with autism spectrum disorder[END_REF][START_REF] Maskey | A Randomised Controlled Feasibility Trial of Immersive Virtual Reality Treatment with Cognitive Behaviour Therapy for Specific Phobias in Young People with Autism Spectrum Disorder[END_REF][START_REF] Newbutt | Brief Report: A Pilot Study of the Use of a Virtual Reality Headset in Autism Populations[END_REF][START_REF] Newbutt | Exploring Communication and Representation of the Self in a Virtual World by Young People with Autism[END_REF][START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Parsons | Virtual Reality in Pediatric Psychology[END_REF][START_REF] Robins | Effects of Repeated Exposure to a Humanoid Robot on Children with Autism[END_REF][START_REF] Spiel | When Empathy Is Not Enough: Assessing the Experiences of Autistic Children with Technologies[END_REF][START_REF] Spiel | Agency of Autistic Children in Technology Research-A Critical Literature Review[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF][START_REF] Tardif | Reducing Information's Speed Improves Verbal Cognition and Behavior in Autism: A 2-Cases Report[END_REF][START_REF] Tsikinas | Design Guidelines for Serious Games Targeted to People with Autism[END_REF][START_REF] Virole | Autisme et tablettes numériques[END_REF][START_REF] Wallace | Sense of presence and atypical social judgments in immersive virtual environments: Responses of adolescents with Autism Spectrum Disorders[END_REF][START_REF] Wallace | Self-reported sense of presence and responses to social stimuli by adolescents with autism spectrum disorder in a collaborative virtual reality environment[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF]. The selected articles were first screened for XR design guidelines, and then sorted according to the emerging concepts coming from the interview analysis. If a literature design guideline suited some emerging concept from the interviews, it was assigned to it. Else, if no relevant concept could be found, a new concept was created, and the guideline was assigned to it. In that case, the already assigned phrasings from the interviews and the literature design guidelines were double checked to see if they could also fit with this new concept. This refactoring process was also applied when concepts gradually changed during the analysis of the interviews.

Results

Stakeholders' insights about autism interventions without and with digital tools are first detailed, and respectively summarized in tables 3 and4 [Table 3][Table 4]. Then, stakeholders' needs are compared with existing XR uses from autism research drawing from two literature reviews [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF], the findings being summarized in table 5. Finally, stakeholders' design insights are compared with XR literature design guidelines, the findings being summarized in table 6. For all tables, concepts and categories are reported from the most to the least reported concept or category according to stakeholders. Throughout the article, the number X of participants mentioning each concept is written inside parenthesis (n=X), next to a literature reference if containing a related guideline. The categories' names are italicized. Participants' quotes were translated from French to English. The term "autistic child" is often employed, as participants mainly spoke about autistic children.

Analysis of common autism interventions

This subsection details common autism interventions according to stakeholders, first without and then with digital tools. For enhanced readability, and due to differences between methods' names in France and in other countries, methods' names are not mentioned, except when important for the overall understanding.

Common non-digital autism interventions

About the intervention context, Individualize the intervention program and Structure the intervention program largely appear (respectively n=33, n=27), as ritualization and strong interindividual differences are common.

Individualization requires practitioners to be "creative", as a psychometrician says, depending on the intended therapeutic outcomes, i.e., starting from the child's interests (n=32) to tailor rewards (n=16) and games (n=10).

For instance, a team supervisor says: "if a child loves the cartoon "Cars" then we'll use boxes with Cars!". Such creativity concerns long-term projects (n=13), the care methods used (n=6), and the sessions (n=14), as they always depend on the child's state (e.g., tired). Though, individualization remains challenging (n=15), being the mostreported sub-concept about difficulties faced in interventions, especially with non-verbal children who require substantial support. About structuration, at the session level, it consists in offering predictability (n=27), of time (n=21) and space (n=19), such as routines (n=17). For instance, a speech therapist always "sets the phone in the drawer to avoid unexpected ringing". This prevents children from getting over aroused due to unexpected stimuli.

Yet, difficulties can also be activity-related (n=14), for instance since providing structured settings may be easier in public institutions. At the intervention program level, different periods of time with different activities are planned (n=11) which last from days to months, depending on children. Practitioners first observe children through free play (n=8), and then leverage their interests to strengthen the dyadic relationship through working activities (n=7). Yet, practitioners warn about not over-using structuration (n=6), as not preparing for real life (n=4).

Regarding the intervention process, most stakeholders advise to Engage children in their intervention program (n=33), to maximize the intended outcomes. This mainly relies on using playful activities (n=30), strengthening the therapeutic alliance (n=30) (i.e., child-practitioner relationship), and using behavioral strategies (n=26). Playful activities derive from developmental methods. The therapeutic alliance consists in building a secure dyadic relationship then allowing to perform challenging tasks. It involves working on the content, with individualized playful activities (n=27), as well as on the context, for instance by adapting the practitioner's behavior (n=19). As an occupational practitioner said: "I whisper, speak quiet, speak up, or speak with Makaton gestures". Behavioral strategies (n=26) mainly include using rewards (n=19) and gradually increasing challenges (n=18). Yet, building the therapeutic alliance remains difficult (n=9), especially with children requiring substantial support (n=9).

Work on sensoriality in intervention (n=26) largely appears due to widespread sensory disorders, with two main concepts, i.e., Work on Sensory Processing Disorders (n=21) and Provide multisensory environmental adaptations (n=20). Practitioners often use sensory habituation to train hypo/hyper sensitivities (n=15). To that respect, multisensory spaces allow "to first remove distressing elements and then to increase them" (n=2). Other practices consist in modulating the audio-visual speed (n=7), or in working on multisensory binding (n=5). Sensory adaptations aim at maximizing attention and engagement, with various techniques. For instance, sensory loads targeting the hyposensitive channels can be used to regulate the child sensorimotor balance (n=13), or sensory protections to protect the hypersensitive channels (n=12), such as protection headphones (n=12).

At last, it is necessary to Assess the state of the individual over time (n=29), on the long (n=28) and on the short terms (n=21). On the long term, evaluations are first conducted at the intervention start, by combining standardized tests about sensorimotor (n=21), and psycho-developmental features (n=18). These tests are mainly based on questionnaires, interviews with relatives and/or the child, and clinical observations (respectively n=9, n=5). Then, combining evaluations at regular time intervals (n=8) allows to infer the child's progress. On the short term, observations are used (n=18) by looking at specific individualized features, e.g., repetitive behaviors (n=2).

Existing uses of digital tools in interventions

According to most participants, digital tools can support common interventions (n=27), as they are engaging (n=2), predictable (n=2), individualizable (n=2), repeatable (n=2), responsive (n=1), stable (n=1), can relieve from human interaction (n=2), and can allow to be wrong (n=1) (see Table 4). Tablets are often used, being intuitive for children (n=4), as well as computers. Participant's interests go beyond social skills, and include three main categories, namely Social skills (n=13), Assistive technologies (n=13), and Mediation/Well-being (n=10), and three minor categories, namely Education (n=8), Sensoriality (n=8), and Diagnosis (n=2). Various games are used to adapt to the child's abilities, the intervention context, and the intended outcomes. Games with simple interfaces, little information, and clear goals are preferred (n=5). To train social skills, social scenarii (n=3) are often used with solo (n=4) or group (n=2) activities. Then, assistive technologies are highly individualized. For instance, a team supervisor mentions the case of a non-verbal autistic child, who knows all Disney cartoons by heart, and uses a tablet to select and play the sentences that she wants to say from them. About mediation/well-being purposes, any appealing game can be used (n=10). A psychometrician notes that "video games allow to get into a prismatic relationship between the screen, the therapist and the child". To minimize adverse effects due to over-exposition to screens (n=5), digital tools must be presented as other activities, such as drawing, and used within a controlled setting, i.e., with an adult and a time limit. Yet, many practitioners remain hostile to using them, as it may increase the distance to the child (n=3), or due to a phantasm to be replaced by machines (n=1).

Comparison between stakeholders' needs and literature XR uses

The findings from the comparison between the stakeholders' insights and the XR systematic reviews [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF] 5].

Mediation and Well-being

Although most participants mention the Mediation and Well-being category (47%), it remains under-researched, only representing three percent of the studies in Mesa-Gresa et al. ( 2018)'s review. Though, [START_REF] Newbutt | Using Virtual Reality Head-Mounted Displays in Schools with Autistic Children: Views, Experiences, and Future Directions[END_REF] previously raised this need, with 29 autistic children answering "It relaxes me and I feel calm" to the question "What could or would you use VR HMDs for?". Participants evoke two main concepts, i.e., Make the child available for performing challenging tasks (n=13), which considers ways to reach a secure state before performing them, and Support the therapeutic alliance through mediation activities (n=6). Three use cases appear. First, use cases draw upon multisensory spaces such as Snoezelen (n=8), to strengthen the therapeutic alliance through secure intermediate XR spaces. Second, use cases are tailored to real-life stereotypic behaviors that children need to use to calm down, e.g., being in a car (n=1). A team director describes them as "derivatives of stereotypies", to "fill some sensory needs in a less stigmatizing way". At last, creative scenarii appear, in line with common interventions (n=3), e.g., music-making (n=2). Yet, as some children may struggle to stop using these appealing environments (n=3), participants suggest to gradually decrease any appealing stimuli before to stop (n=1).

Social and Cognitive Training

Whereas 41% of the stakeholders mention the Social and Cognitive Training category, more than 87% of the studies from the two literature reviews are connected to it [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF]. Reallife use cases mostly appear, with two main concepts, i.e., Train socio-emotional & Interactional abilities (n=14) and Train cognitive abilities (n=6). The first concept consists in gradually habituating the child to daily social situations through a secure XR space. To that respect, task-dependent features can be modulated (e.g., number of people) in various aversive situations (n=12) (e.g., medical examinations (n=6)), to promote the generalization of the skills learned into real life. Then, cognitive abilities include daily living skills (n=4), at home (e.g., brushing teeth) or outside (e.g., buying things in a supermarket). Other cognitive skills are mentioned (n=3), such as attentional abilities [START_REF] Escobedo | Using Augmented Reality to Help Children with Autism Stay Focused[END_REF], inspired from behavioral (e.g., ABA) (n=1) or educational approaches (e.g., Boehm-3) (n=1) [START_REF] Boehm | Boehm test of basic concepts: Boehm-3 kit form E[END_REF]. Yet, such scenarii would only benefit individuals requiring low support, being able to understand them. An autistic participant also stresses that "No manual could ever cover all possible situations". Indeed, a psychometrician reports the case of an autistic adult who had learned the "right" way to greet people and got lost at work due to the variety of situations encountered.

Sensoriality

Whereas participants highly mention the Sensoriality category (38%), including all psychometricians and occupational therapists, it remains under-explored in the literature. Indeed, only the SEMI project [START_REF] Magrini | Augmented Interaction Systems for Supporting Autistic Children. Evolution of a Multichannel Expressive Tool: The SEMI Project Feasibility Study[END_REF] focuses on training motor skills, using a kinect camera and four distinct applications. Three main concepts appear, i.e., Rehabilitate sensory disorders (n=10), Assess sensory disorders (n=6), and Work on action-reaction principles (n=4). Two main use cases emerge from the interviews: gradually adding stimuli to reach the tolerance thresholds, and then conduct sensory habituation; or gradually removing stimuli from a multisensory scene to assess the tolerance thresholds. A psychometrician says: "the challenge is to recreate contexts for assessing the tolerance thresholds while conducting a therapy". Possible scenarii range from real-life (n=7) to multisensory (n=6) spaces, depending on practitioners' preferences and the child's abilities. For instance, they include a supermarket with adjustable stimuli (e.g., dimming the lights) or Snoezelen-like spaces. A psychologist stresses that working on sensory disorders allows to better include non-verbal individuals with cognitive impairments. At last, an occupational therapist warns about the impossibility to recreate the richness of real-life stimuli in XR.

Assistive Technologies

Although some participants mention the minor category Assistive technologies (15%), it is absent from the two literature reviews considered. Two main concepts appear: Provide context relevant-only information (n=4) and Support sensory strategies (n=1). The first one can be achieved by adding and/or removing contextual information, e.g., adding information about the emotions of people around (n=1), or filtering a distressing noise (n=1). The second one aims at making the child secure enough to then be able to perform challenging tasks. To that respect, a participant suggests creating a tipi-like space augmented with sounds and colors, inspired from a child who could enter a tipi-like space in his classroom when feeling overwhelmed to get resourced and then go back to his class.

Comparison between stakeholders' XR design insights and literature guidelines

This section draws design guidelines from the comparison between the interviews' findings and the literature (see table 6) [Table 6]. Its subsections follow the main categories that were derived from the grounded theory process.

Task design

Individualization is advised to cater for children and practitioners, regarding both the content [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Parsons | Virtual Reality in Pediatric Psychology[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF]n=15) (e.g., stimuli, tasks), and the medium [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]n=1). For instance, a psychometrician mentioned using video games as "modelling dough", i.e., by adjusting every possible parameter. Whereas participants mainly suggest displaying familiar XR content (n=14) (e.g., drawings), the literature focuses on adapting the way the environment works (e.g., number of stimuli), sometimes with physiologically informed platforms [START_REF] Krishnappa Babu | Gaze-Sensitive Virtual Reality Based Social Communication Platform for Individuals with Autism[END_REF][START_REF] Kuriakose | Design of a Physiology-Sensitive VR-Based Social Communication Platform for Children With Autism[END_REF].

As in common interventions, engagement aims at maximizing the intended outcomes. According to the participants and the literature, it requires to tailor the environmental motor and cognitive complexity to the child's abilities and to the intervention context [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF]n=13). It also relies on offering predictable and simplified audiovisual content to prompt discovery [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF], including some unexpected events [START_REF] Alcorn | Motivating children's initiations with novelty and surprise: initial design recommendations for autism[END_REF][START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Virole | Autisme et tablettes numériques[END_REF]n=3), to create a "slight strangeness", as a psychologist said. Using common NDBI principles is advised, i.e., rewards, imitation, and sense of agency. Rewards must be tailored to the performance [START_REF] Constantin | Designing computer-based rewards with and for children with Autism Spectrum Disorder and/or Intellectual Disability[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]. About imitation, the practitioner may imitate the child, or conversely, with promising outcomes over the therapeutic alliance and the training [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]n=1). Supporting the sense of agency then consists in making the child active [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Spiel | Agency of Autistic Children in Technology Research-A Critical Literature Review[END_REF]n=14), possibly with authoring activities [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]n=3), e.g., drawing upon the painting VR game Tiltbrush (Ying-Chun and Chwen-Liang 2018; n=2). All these features and other strategies [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Kerns | Attention and working memory training: A feasibility study in children with neurodevelopmental disorders[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF][START_REF] Tsikinas | Designing effective serious games for people with intellectual disabilities[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF]n=5), such as using a scoring system [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Kerns | Attention and working memory training: A feasibility study in children with neurodevelopmental disorders[END_REF] promote the child's fun.

Considering autism sensoriality and perception allows to create well-suited designs for children from the entire spectrum. To that respect, structuring the time and space is advised [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF]n=8), e.g., using time timers and allowing to rehearse actions [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Lorenzo | The application of immersive virtual reality for students with ASD: A review between 1990-2017[END_REF]n=10). Due to sensorimotor disorders, accessible interactions are preferred, such as touchless interaction [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]n=4), as well as offering varied interaction possibilities [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]. To move in space, embodied interaction is preferred over teleportation techniques [START_REF] Bartoli | Designing and evaluating touchless playful interaction for ASD children[END_REF][START_REF] Bozgeyikli | Virtual Reality Interaction Techniques for Individuals with Autism Spectrum Disorder: Design Considerations and Preliminary Results[END_REF][START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF]n=1). Finally, drawing links with the real world is advised to make experiences meaningful, e.g., including familiar objects into XR [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF]n=1), and by considering autism perception during the design process, e.g., associative thinking [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]Virole, 2014, n=2).

Collaboration possibilities must be offered, as the child-practitioner relationship is at the core of interventions.

Hence, practitioners have to be able to prompt children [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]n=2), while children can see them in order to be reassured [START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF]n=10). Moreover, controls must be shared between them (n=10) so that the child can be active. Indeed, a psychometrician suggests that the impossibility in many VR applications to be with the patient decreases practitioners' acceptability. According to two participants, the practitioner must be visible only if context-relevant regarding the XR scenario, e.g., for medical examinations.

Protocol to conduct XR sessions

Stakeholders insist on creating a secure context to reduce potential biases, possibly due to participants' anxiety.

Before and during sessions, it consists in offering predicability [START_REF] Garzotto | Wearable Immersive Virtual Reality for Children with Disability: a Case Study[END_REF]n=5), making the experience meaningful [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]n=4), and supporting engagement [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]n=8). In the long run, it relies on including the XR experiment as part of the overall intervention [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Robins | Effects of Repeated Exposure to a Humanoid Robot on Children with Autism[END_REF]n=4), and/or on planning a free play period to get the child accustomed to the system (n=3).

Mixed methods (i.e., qualitative and quantitative methods) that are adapted to children's abilities may help to assess their experience. Although no consensus exists in the literature, and a comprehensive overview is beyond the scope of this paper, our analysis suggests major practices. Before sessions, clinical questionnaires may be used to assess developmental and sensorimotor abilities [START_REF] Malihi | Short report: Evaluating the safety and usability of head-mounted virtual reality compared to monitor-displayed video for children with autism spectrum disorder[END_REF][START_REF] Maskey | A Randomised Controlled Feasibility Trial of Immersive Virtual Reality Treatment with Cognitive Behaviour Therapy for Specific Phobias in Young People with Autism Spectrum Disorder[END_REF]. A quantitative analysis of behavioral and physiological data before and during sessions may help to infer the child's state [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Koirala | An Exploration of Using Virtual Reality to Assess the Sensory Abnormalities in Children with Autism Spectrum Disorder[END_REF][START_REF] Kuriakose | Design of a Physiology-Sensitive VR-Based Social Communication Platform for Children With Autism[END_REF]. Then, custom questionnaires, often selfreport, are often used to assess engagement [START_REF] Aruanno | HoloLearn: Wearable Mixed Reality for People with Neurodevelopmental Disorders (NDD)[END_REF][START_REF] Garzotto | Wearable Immersive Virtual Reality for Children with Disability: a Case Study[END_REF][START_REF] Garzotto | Magic Room: A Smart Space for Children with Neurodevelopmental Disorder[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF], along with standardized XR questionnaires, e.g., targeting the feeling of presence [START_REF] Wallace | Sense of presence and atypical social judgments in immersive virtual environments: Responses of adolescents with Autism Spectrum Disorders[END_REF][START_REF] Wallace | Self-reported sense of presence and responses to social stimuli by adolescents with autism spectrum disorder in a collaborative virtual reality environment[END_REF]. Evaluations must consider the practitioner's impact over the child [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]. Their comparisons at regular time intervals may yield insights about the child's evolution. Such evaluations can be combined with qualitative evaluations, i.e., observations [START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF]n=2), or interviews with practitioners, relatives, and the child if possible [START_REF] Spiel | When Empathy Is Not Enough: Assessing the Experiences of Autistic Children with Technologies[END_REF]n=1). Yet, a psychiatrist says that assessing the intervention outcomes remains challenging, as "during the week the child does 300000 things".

Design process

Creating autism-friendly environments requires using participative design [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Brosnan | Look up! Digital technologies for autistic people to support interaction and embodiment in the real world[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Spiel | Agency of Autistic Children in Technology Research-A Critical Literature Review[END_REF]n=5), to consider all stakeholders' needs, including autistic individuals requiring substantial support [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]n=7). According to the participants and the literature, equipment choices must depend on: the healthcare context, e.g., being affordable [START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]n=2); the child's abilities, e.g., being resistive and non-tethered [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF][START_REF] Newbutt | Brief Report: A Pilot Study of the Use of a Virtual Reality Headset in Autism Populations[END_REF]n=1) ; and the XR tasks [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], e.g., using AR to prompt the generalization of skills. Whereas four participants are reluctant about using HMD with autistic children, mainly due to risks of isolation (n=2), the other participants advocate for a controlled use, namely, with a practitioner.

Yet, practitioners stress that the acceptability and usability may be child-dependent (n=9). Moreover, to not induce anxiety, wearing the HMD may require using sensory habituation beforehand (n=3), and conducting the experiment in the usual clinical setting of the child [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]n=1). At last, although manufacturers recommend using XR from the age of 13 [START_REF] Gent | Are Virtual Reality Headsets Safe for Kids? livescience[END_REF], participants advocate for using task-dependent recommendations, based on the child's abilities and the practitioner's expertise (n=7), e.g., 7/8 for sensory-based and relaxation purposes (n=2), and 10/13 otherwise (n=5).

Information presentation

Displaying little and clear information is advised due to autism filtering difficulties, i.e., only task-relevant stimuli [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Virole | Autisme et tablettes numériques[END_REF], and audiovisual simplification [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF]n=4). Adapting to the child's pace may also support understanding, e.g., adjusting the information speed [START_REF] Tardif | Reducing Information's Speed Improves Verbal Cognition and Behavior in Autism: A 2-Cases Report[END_REF]n=13). Indeed, as a psychometrician said, "learning requires slowness".

The level of details and the realism of the graphics must be task-dependent (n=7), e.g., realistic for social scenarii (n=5), and abstract and creative for mediation purposes (n=1). To that respect, a psychologist stressed that "realistic and non-realistic environments won't interest the same practitioners" (n=1). About social scenarii, adjustable collaborative realistic settings are advised to train various skills, and especially turn-taking [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF].

Since little information is advised, simplified cartoonish avatars with customization possibilities are preferred to represent the others as well as the self [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Newbutt | Exploring Communication and Representation of the Self in a Virtual World by Young People with Autism[END_REF]n=1). The avatar of the child has to be positioned at real-world height [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]. Moreover, due to common perceptual filtering difficulties, only hearing others' avatars instead of both hearing and seeing them can be preferred [START_REF] Newbutt | Exploring Communication and Representation of the Self in a Virtual World by Young People with Autism[END_REF].

Discussion

Summary of Results

The first objective of this article was to check whether autism stakeholders' XR needs matched the existing XR uses. Our comparison between 34 interviews, mainly conducted with practitioners, and the literature, revealed that whereas more than 87 percent of the studies focus on training socio-emotional abilities, participants mentioned three main XR objectives, i.e., well-being and mediation, social and cognitive training, and sensoriality (see table 5). These objectives simultaneously draw upon the main features of practitioners' interventions without or with digital tools (see tables 3 and4). This gap calls for more research to explore XR sensory-based and mediation approaches, and more considering autistic individuals requiring high support. These objectives are also strongly inclusive and bridge the gap between a mere focus on training abilities and an only focus on changing the society to improve the well-being of autistic individuals. To that respect, our findings extend [START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF]'s research roadmap for the XR medium. Possible use cases that implement these categories, and particularly benefit from using AR, are discussed in the next subsection. The second objective of this article was to provide XR design guidelines that are representative of autism stakeholders. Whereas the guidelines from the interviews and XR autism literature presented similarities, gaps also emerged (see table 6). More specifically, stakeholders advocated for paying more attention to the intervention context and for using more collaborative designs. XR design guidelines are outlined in the third subsection, followed by limitations to this work.

Suggestions of Use Cases for Future Autism XR Research

To train social abilities, using VR social scenarii (e.g., school playground) with a precise control of all stimuli by the practitioner are suggested. Yet, due to the autism literal way of learning, more research is needed to maximize the generalization of skills learned from VR into real-life [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]. Moreover, whereas quickly shifting between different use cases could enhance the intended outcomes [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], two participants stress that the richness of real-life situations could not be recreated. Hence, VR training should be considered as part of the overall intervention program, and within a gradual transition from VR to AR and finally real life. For instance, a bakery scenario consisting in buying bread could first be trained in VR, to limit possible anxiety, and then in a real bakery, using AR to withdraw distressing information (e.g., lights) and add contextual elements (e.g., emotion detection). This VR-AR progression could help to gradually work in more ecological contexts due to AR capabilities [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF], and to maximize the generalization of the skills learned by gradually confronting the child to the unpredictability of real-life. These finding extend the complementary training and prosthetic roles previously assigned to VR and AR by [START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF].

To make the child in an optimal secure state, three XR sensory-based approaches which draw upon common interventions emerged, i.e., multisensory relaxing spaces, derivatives of stereotypies, and mediation spaces.

Creating collaborative multisensory relaxing XR spaces largely emerged, often Snoezelen-inspired. A psychometrician described them as "sensory backpacks". To that respect, whereas VR can offer a precise control over all stimuli, it also displays risks of isolation [START_REF] Parsons | The potential of virtual reality in social skills training for people with autistic spectrum disorders: Autism, social skills and virtual reality[END_REF]. Moreover, due to common autistic proprioception and symbolization difficulties, children could misunderstand the avatar representations of themselves and the practitioner. Thus, this could prevent the use of such scenarii for children needing high support.

Even if AR also presents risks of isolation [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF], AR sensory approaches could overcome these issues by perceiving the real surroundings and not using avatars. Thus, their low appearance in surveys [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF] calls for more research. Possible use cases include real spaces where the proportion of real and virtual elements could be adapted to the session's needs, e.g., withdrawing posters on walls. Some participants advise creating XR derivatives of stereotypies to replace with a non-stigmatizing XR approach the repetitive behaviors that children often use to calm themselves but are often considered as non-socially appropriate. Regarding that unexplored approach, both VR and AR call for more research. VR use cases could be considered if a whole context must be recreated. For instance, one team supervisor mentioned the case of a boy who needs to be driven by his parents on Paris ring-road to get relaxed. Recreating this context in VR could support both the boy and his family. AR could be also used for recreating specific elements, e.g., spinning objects.

At last, XR mediation activities focus on strengthening the therapeutic alliance through collaborative free play activities, to prompt symbolization processes, as common mediation activities [START_REF] Brun | L'acte de création et ses processus dans les médiations thérapeutiques pour enfants autistes et psychotiques[END_REF]. Yet, whereas the activity theory (Engeström et al., 1999) considers technology as mediating tools that encourage social processes, they remain unexplored in XR. Yet, according to a psychologist, this approach raises some psychology research questions, for instance to explore the concept of potential space [START_REF] Winnicott | Jeu et réalité: l'espace potentiel[END_REF], i.e., an intermediary area between the subjective experience and the objective reality for playful and creative experiences. Such approaches could draw upon previous non-XR digitally-augmented multisensory experiences which displayed promising outcomes about the therapeutic alliance [START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Garzotto | Magic Room: A Smart Space for Children with Neurodevelopmental Disorder[END_REF][START_REF] Gelsomini | Magika, a Multisensory Environment for Play, Education and Inclusion[END_REF][START_REF] Mora-Guiard | Sparking social initiation behaviors in children with Autism through full-body Interaction[END_REF][START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF][START_REF] Ringland | SensoryPaint: a multimodal sensory intervention for children with neurodevelopmental disorders[END_REF]. They allowed to trigger multiple stimuli through body movements and various interfaces (e.g., reactive surfaces). Mediate was conducted in a large space [START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF], Magic Room [START_REF] Garzotto | Magic Room: A Smart Space for Children with Neurodevelopmental Disorder[END_REF], Magika [START_REF] Gelsomini | Magika, a Multisensory Environment for Play, Education and Inclusion[END_REF], Sensory Paint [START_REF] Ringland | SensoryPaint: a multimodal sensory intervention for children with neurodevelopmental disorders[END_REF]Land of Fog (Mora-Guiard et al., 2017) took place in smaller spaces, and Responsive Dome Environment relied on a dome-like space [START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF]). Yet, these bespoke projects can be expensive and/or lack of flexibility. XR research should consider overcoming these limits with HMD-based AR.

XR sensory-based playful activities allow to assess or rehabilitate sensory disorders, or work on action/reaction principles, often by gradually adding/removing stimuli. VR and AR both provide solutions for creating such scenarii. The first half of the participants mention VR Snoezelen-like scenarii. The other half mentions realistic scenarii ranging from VR to AR, for instance by starting in a controllable VR space, and gradually going to AR.

A possible use case could consist in recreating a VR supermarket, and then work in the real supermarket while using AR to remove distressing elements and add contextual help. Such AR setups could also be used as daily compensation strategies, in line with common strategies (e.g., protection headphones). Hence, AR appears as highly inclusive, since it allows children to enter spaces usually considered as overwhelming. While such sensorybased AR scenarii remain under-explored, the current evolution of HMDs calls for more research in this area.

Suggestions of XR Autism Design Guidelines

XR task design draws upon many common intervention principles (see table 3), e.g., individualization, structuration, gradual challenges, or offering a sense of agency. Yet, contrary to the literature, stakeholders emphasize the importance of creating collaborative designs, as the success of common interventions largely relies on the therapeutic alliance. To that respect, AR seems promising, as it allows to connect with the familiar environment of the child, by perceiving the usual practitioners and not using avatars. Then, two practitioners remarked that many design requirements that are listed in table 6 draw from common educational practices, and in particular the ones of [START_REF] Piaget | The Psychology of the child (Nachdr.)[END_REF] and [START_REF] Montessori | The Montessori method[END_REF]. As these practices often advise to use handling activities, and as AR can easily be combined with tangibles, AR seems well-suited to extend them.

Methodological insights expand previous XR recommendations [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF], by suggesting to focus on two aspects of the intervention: the context, and the evaluation of the outcomes. About the context, creating a secure space to then be able to conduct experiments was less emphasized in the literature to our knowledge. On the short term it consists in offering predictability, i.e., before, during and after the session. To that respect, AR seems well-suited, due to the reasons above-mentioned. On the long term, XR protocols may split into two periods, i.e., first set the child in a secure state, and then train specific abilities. To assess the XR intervention outcomes, mixed methods (i.e. qualitative and quantitative methods) can be used to adapt to the diversity of autistic profiles.

Although it remains challenging due to the overall intervention that children take part in, regular evaluations may help to infer their evolution over time. So far, no standardized XR questionnaire exists to assess the autistic user's experience, and XR studies mainly focus on observable features. Yet, some custom questionnaires have been created. For instance, [START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF] suggest to focus on four main features, i.e., the impact of photorealism, the understanding of real vs. virtual elements, the body movements, and the active exploration.

Creating such questionnaires leads to reconsider some commonly measured aspects with non-autistic individuals which affect autistic users differently. For instance, assessing the feeling of presence, i.e., the feeling of "being here" [START_REF] Biocca | The Cyborg's Dilemma: Progressive Embodiment in Virtual Environments[END_REF], can already lead to ambiguous results with non-autistic children, and is even more questionable with some autistic children who may struggle to say if they feel present in real-life [START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF]. Moreover, whereas photorealism may engage non-autistic users, it may distract autistic users [START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF]. At last, self-report questionnaires that are used in most studies [START_REF] Newbutt | Using Virtual Reality Head-Mounted Displays in Schools with Autistic Children: Views, Experiences, and Future Directions[END_REF] cannot be used for individuals with intellectual impairments. This calls for more research to create such questionnaires, to be filled by practitioners, as well as the child if possible, in line with [START_REF] Aruanno | HoloLearn: Wearable Mixed Reality for People with Neurodevelopmental Disorders (NDD)[END_REF]'s study. They could also be combined with physiological data to get anxiety markers, e.g., heart rate [START_REF] Kuriakose | Design of a Physiology-Sensitive VR-Based Social Communication Platform for Children With Autism[END_REF]). Yet, more research is also needed to understand which relevant factors allow to get insights about complex perceptions (e.g., engagement), while using low intrusive technologies, such as light bracelets [START_REF] Simões | Virtual Travel Training for Autism Spectrum Disorder: Proof-of-Concept Interventional Study[END_REF]. About the design process, using participative design is advised, as suggested by prior research [START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF], as well as conducting studies in clinical settings. Equipment choices must be made accordingly, depending both on the use context and on the intended task. While most stakeholders are positive about using HMDs, in line with the literature, they suggest that they must be used in a controlled way, i.e., with a practitioner. This paper also reveals that participants would prefer using task-dependent age recommendations, e.g., eight years old for mediation applications focusing on well-being purposes. This was absent from the literature to our knowledge. About information presentation, in addition to simplifying the audiovisual content, in line with the 2D games that often appeal to autistic individuals (see table 4), and with [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]' findings, this paper suggests to adapt the graphics' realism both to the intended task and to the practitioners' preferences. Indeed, depending on the type of intervention that practitioners use (e.g., NDBI, or psychodynamic), they may prefer using non-realistic creative scenarii, or realistic scenarii. Giving control over the audiovisual speed and prosody is also advised, as in [START_REF] Tardif | Reducing Information's Speed Improves Verbal Cognition and Behavior in Autism: A 2-Cases Report[END_REF]'s study. Indeed, decreasing the audiovisual speed may increase the child's understanding. At last, adding some unexpected events within a highly-structured XR space to enhance engagement connects with [START_REF] Remington | Implications of capacity in the classroom: Simplifying tasks for autistic children may not be the answer[END_REF]'s findings, which stress that using too little or too many distractors may hinder the attention of autistic children. This recommendation is also linked with common compensation strategies that individuals with Attention-Deficit Hyperactivity Disorder use to focus. Hence, future XR autism research may consider neurodevelopmental disorders in general, due to its potential impacts beyond the scope of autism.

Limitations

Findings must be considered in the light of some limitations. Interviews were mainly conducted with practitioners, since XR guidelines aimed at supporting their interventions. Yet, this may have led to less consider the views of autistic individuals. Moreover, no single stakeholder could expertly provide insights about XR, but only suggestions based on their knowledge of common interventions with or without digital tools.

The evaluation of the included publications in terms of design features was conducted qualitatively and may contain inaccuracies. Also, no systematic literature review of XR design guidelines was made, and the articles were mainly hand-searched. Conducting such a systematic review about XR design guidelines and comparing it with our interviews' findings may yield further design insights.

The evolution of the understanding of the autism field by the first author throughout the interview process may have gradually changed his way to ask questions to the interviewees, and to adapt to them. This also may have led to elicit more answers over time. Elements from the first author' background also may have influenced the of the grounded theory analysis. At last, as the first author is not a native English speaker, translating interviews from French to English may have led to inaccuracies, even if efforts were made to remain close to the original wordings during the process.

Only interviewing French speaking participants may have led to overlook some insights, possibly being more prominent with international stakeholders. This calls for future research to complement the present study by interviewing stakeholders from different countries and comparing their standpoints with our findings.

To complement and extend the findings from this paper, it will be particularly useful to conduct XR participative design workshops with autism stakeholders being representative from all autism fields.

Conclusion

XR autism research displays a strong potential for complementing existing common autism interventions due to embodied immersive multisensory capabilities. Though, most autism XR studies focus on training socio-emotional abilities and concern children requiring low support. To get insights over common interventions, and then derive XR use cases and designs that could better support practitioners and could concern the entire spectrum, 34 interviews were conducted with stakeholders, mainly including practitioners. They were then analyzed using a grounded theory approach, involving three steps. First, a classification of the data according to concepts and categories was built from the interviews. Second, emerging XR use cases from the interviews were compared with two systematic literature reviews [START_REF] Berenguer | Exploring the Impact of Augmented Reality in Children and Adolescents with Autism Spectrum Disorder: A Systematic Review[END_REF][START_REF] Mesa-Gresa | Effectiveness of Virtual Reality for Children and Adolescents with Autism Spectrum Disorder: An Evidence-Based Systematic Review[END_REF] to look for potential gaps between practioners' needs and the objectives of existing studies. Finally, XR design guidelines were obtained by comparing the findings from the interviews with an autism XR literature survey that was built in relation to our emerging grounded theory. Findings reveal that most stakeholders already use technology-based approaches to support interventions, often with tablets and desktop computers. Drawing upon them, as well as common nondigital interventions, they were interested in three main categories of XR use cases: (a) mediation and well-being, (b) social and cognitive training, and (c) sensoriality. In addition to these categories, technical and practical guidelines emerged. The main technical guidelines suggest that future research should consider using AR rather than VR to target children from the entire spectrum. Indeed, AR appears to be more inclusive and ecological than VR, as it allows to perceive the real child's surroundings. Moreover, gradually going from VR to AR seems promising to prompt the generalization of the skills learned into real life. To do so, the practitioner could handle the real-virtual proportion depending on the child's abilities. The main practical guidelines suggest that XR designs should include collaboration capabilities. Furthermore, XR studies should be considered as part of the child's overall intervention program, for instance by conducting studies within the usual clinical setting of the child. Table 1. Profiles of the participants

Figure Caption Sheet

  (2021)'s study which extends NDBI to XR, no XR design recommendations are rooted in common interventions. Thus, a new set of XR user-centered design guidelines must be derived, informed by stakeholders' insights about common interventions, and by stakeholders' insights about XR guidelines in comparison with the existing XR autism literature. This paper aims at offering such guidelines. The contributions of this paper are threefold. First, common practices of autism interventions are presented based on 34 semi-structured interviews with autism stakeholders, mainly including practitioners. Second, potential XR uses for autism interventions are derived from a comparison between the interviews' findings and the findings from two systematic reviews about XR autism interventions

  are presented following four main categories which emerged from the analysis: Mediation and Well-being (n=16), Social, Education and Cognitive Training (n=14), Sensoriality (n=13), and Assistive technologies (n=5) (see Table 5) [Table

Figure 1 .

 1 Figure 1. Method used to conduct and analyze the semi-directed interviews

Table 2 .

 2 Semi-directed questionnaire addressed to the participants

Basis of question Additional keywords/phrasings to ask for more details Phase 1: Demographics Q1

  -Common approaches used in interventions NDBI/psychodynamic/sensory-based, etc.; collaboration with others. Q2 -Practitioner's background with respect to autism interventions Years of experience; private or public sector. Typical autism intervention (removed for non-practitioners) Examples of easy and/or difficult session. Q4 -Evaluation methods used before/during intervention Sensory profile; impact of sessions; generalization of skills; role of relatives. Q5 -Individualization of intervention over time Number and planning of the sessions; impact of atypical perception. Q6 -Common intervention practices (added after the 6 th interview) Typical exercises; difficulties experienced; rewards; individualization; relationship with the practitioner; structuration of time and space; routines. Q7 -Use and role of playful activities during sessions Motivation; engagement. Q8 -Multisensory rehabilitation practices Tools; environments; type of stimuli (visual, audio, tactile); method used. Q9 -Mediation practices in interventions Music; dance; fine art; relationship with the practitioner. Q10 -Digital tools already used by the practitioner, and possible needs or viewpoints to that respect (more explored with academics) Medium (i.e., tablets, robots, VAR); examples of games; collaboration with the practitioner; acceptability by children and practitioners; ideal digital tool. Q11 -Virtual or augmented reality environments that the practitioner would be interested in (more explored with academics) Adaptability; evaluation; sensory processing disorders; social aspects; covering the entire autism spectrum. QA1 -Views about common interventions (for autistic participants) QA2 -Atypical autistic perception (for autistic participants)

	Phase 2: Interview body Q3 -Phase 3: Q12 -Any element that the practitioner would like to add	--
	Ending	Q13 -Other relevant experts to contact

This article uses autism stakeholders' preferences in terms of terminology, such as identity-first language (e.g., autistic people) (Bottema-Beutel et al.

2021).

Start from the child's interests (n=32)

Create game depending on the purpose (n=10) Game must depend on child's interests (n=4), skills (n=2), fears (n=1) Individualize rewards (n=16) Individualize communication method (n=17) Use alternative communication system (n=16)

Use pictograms / gestures, e.g., PECS (n=14) & Makaton (n=7) systems Communicate through mediation activites (n=4)

Use any game (n=3) or object (n=1) Individualize sessions (n=14)

Session has to depend on the child's state, e.g., fatigue (n=6) Build personalized project (n=13)

Set personalized long-term goals based on evaluations (n=13) Individualize care method (n=6)

No method suitable for every child exists (n=6) Use mediation activities (n=24), e.g., music (n=14), fine arts (n=5) Use any appealing games (n=12), e.g., video games (n=5) Use autistic interests: sensory stimulation (n=6), music (n=5), machines (n=4), geometric shapes (n=3), things that spin (n=3), bubbles (n=3)

Engage

Adapt the practitioner's behaviors depending on the child (n=19)

Be slow and enveloping (n=12), e.g., adjust voice intensity (n=4), Do not over anticipate (n=3), Adopt the child's pace (n=2) Provide meaningful explanations (n=8) Understand the "autistic world" (n=8), e.g., Allow stereotypies (n=1) Create a secure relationship with the child (n=14)

Create a secure relationship (n=9); Enjoy the activity conducted (n=7)

Use playful activites (n=26)

Adapt game based on the intervention goal (n=25) Goal can be social (n=13), cognitive (n=5), sensory (n=4) Entertain the child and widen his interests (n=4) Increase the child's autonomy (n=2) Use behavioral strategies (n=26) Use rewards (n=19)

Use sensory-based rewards (n=9), the token economy method 1 (n=5), or verbal congrats (n=4)

Gradually increase the challenge (n=18) Gradually adjust sensory loads (n=13), helping strategies (n=3), number of elements (n=3), therapist place (n=1) The child imitates the practitioner (n=7) Use physical prompts (n=4) Set things available to prompt demands (n=3) Provide a sense of agency (n=16)

Give choice over a few tasks (n=16), offer possibilities to move (n=1) Task can be done sitting (n=3), moving (n=3), outside (n=1)

Use compensation strategies to relax the child (n=14)

Make the child available for performing challenging tasks (n=12)

Use sensory stimulation (n=7), relaxing activity (n=4), start from stereotypic behaviors (n=2) Give daily strategies to prevent meltdowns (n=4)

Use derivatives of stereotypies (n=2) Listening lottos are listening games where the child has to listen to the sounds that are presented and then to associate them with the corresponding images.

Assess

Table5. Fields of interests of the participants regarding XR use cases for autism interventions

Content

Individualize content: Vary the tasks, interactions, stimuli, graphics [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Parsons | Virtual Reality in Pediatric Psychology[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF], add familiar objects into XR [START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF], or onto the realenvironment with AR [START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF]

Discovery

Prompt discovery: Use various non-concurrent elements [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF], e.g., movement [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF], shapes [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF], audiovisual stimuli [START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF], 3D animations [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF], as well as unexpected elements [START_REF] Alcorn | Motivating children's initiations with novelty and surprise: initial design recommendations for autism[END_REF][START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Virole | Autisme et tablettes numériques[END_REF] Prompt discovery: Use unexpected elements (n=3), use various non-concurrent elements (e.g., audiovisual stimuli surrounding the child) (n=1)

Broaden the child's attention [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]: Use eye-tracking to detect fixations.

Body perception

See oneself in XR [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF] See oneself in XR (n=1): See one's shadow (n=1)

Environmental arrangement

Gradually increase/decrease: motor and cognitive complexity [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF], i.e., number of elements (e.g., crowdedness, stimuli, dynamism) [START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF] or types of elements (e.g., shapes, avatar's reactions, instructions, gestural prompts) [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF] Gradually increase/decrease (n=13): number and types of stimuli (n=8), realism level (for social scenarii) (n=4), predictability (n=3), environment neutrality (n=3), number of controllable elements (n=1), number of distractors (n=1), dynamism (n=1), prompts (n=1)

Rewards

Individualize rewards [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF]: Use personal [START_REF] Kientz | Interactive Technologies for Autism[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF] sensory-based [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF] or generic [START_REF] Constantin | Designing computer-based rewards with and for children with Autism Spectrum Disorder and/or Intellectual Disability[END_REF] rewards, often assess new child's rewards [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF] Individualize rewards (n=1)

Adjust rewards: Consider the child's performance and progression (e.g., antecedents and behaviors) [START_REF] Constantin | Designing computer-based rewards with and for children with Autism Spectrum Disorder and/or Intellectual Disability[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], as well as the child's abilities [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF] Sense of agency Make the child feel in control [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Spiel | Agency of Autistic Children in Technology Research-A Critical Literature Review[END_REF]: Use child-initiated episodes (e.g., from what they like, or by making them choose between different actions/activites/game pathways) [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF][START_REF] Whyte | Designing Serious Game Interventions for Individuals with Autism[END_REF], adjust the information speed [START_REF] Tardif | Reducing Information's Speed Improves Verbal Cognition and Behavior in Autism: A 2-Cases Report[END_REF], make the environment respond to various actions (e.g., gestures, voice) [START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF] Make the child feel in control (n=14): Use child-initiated episodes (e.g., from what they like, or by making them choose between different activities (n=6)), give them the possibility to freely move in space (n=2)

Allow the user to author the XR environment [START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF] Allow the user to author the XR environment (n=3): Record and repeat sounds or videos (n=3)

Imitation

Use modelling partners who simulate situations [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], e.g., peers, avatars Use modelling partners who simulate situations (n=1) Use avatars who imitate the child [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], e.g., language, play, and body movements Use avatars who imitate the child (n=1)

Sensoriality & perception

Structuration of time & space

Offer predictability [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF]: Avoid loud sudden sounds [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF] Offer predictability (n=8): Use little distractors (n=6), use visual activity timers (n=3), alert about the presence of stimuli (n=2) Give repetition possibilities [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Lorenzo | The application of immersive virtual reality for students with ASD: A review between 1990-2017[END_REF]): e.g., routine in training [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF] Give repetition possibilities (n=10)

Interaction types

Use accessible interaction types [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF], e.g., speech recognition [START_REF] Halabi | Design of Immersive Virtual Reality System to Improve Communication Skills in Individuals with Autism[END_REF], or touchless interaction [START_REF] Bartoli | Designing and evaluating touchless playful interaction for ASD children[END_REF] Use accessible interaction types (n=4): ergonomic controllers (n=4), tangibles XR controllers (n=3) Offer various ways to interact [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF] Use motion-based embodied interaction [START_REF] Bartoli | Designing and evaluating touchless playful interaction for ASD children[END_REF][START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF][START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF] Use motion-based embodied interaction (n=1): no teleportation (n=1)

Meaningful experiences

Draw links with the real world [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Tang | Designing a Serious Game for Youth with ASD: Perspectives from End-Users and Professionals[END_REF] Draw links with the real world (n=1) Make experiences meaningful [START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF]: Consider autism perception, e.g., visual memory [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF], and associative way of thinking [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Virole | Autisme et tablettes numériques[END_REF] Make experiences meaningful (n=1): Use individualized communication system of the child in XR (n=1)

Collaboration

Prompting & Reassurance

A practitioner/relative can prompt the child [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF], e.g., instructions, gestures, physical prompts

The practitioner/relative can prompt the child (n=2), e.g., to help (n=2)

The child can see the practitioner, e.g., for reassurance [START_REF] Dautenhahn | Design Issues on Interactive Environments for Children with Autism[END_REF] The child can see the practitioner

Secure environment

Give predictability: Practitioners may wear the HMD and suggest the child to handle it before to wear it [START_REF] Garzotto | Wearable Immersive Virtual Reality for Children with Disability: a Case Study[END_REF] Give predictability (n=5): Make the planning clear before to start (n=3), use pictograms showing what the XR space will look like (n=1), practitioners may wear the HMD before the child (n=1) Make the experience meaningful for the child: Combine different elements and strategies [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF] Make the experience meaningful for the child: Use understandable vocabulary to present the experience (n=4), make sure everything is understood prior to start (n=2) The practitioner can control every XR parameter (n=9): See what the child sees (n=2)

Organization of sessions

Get the child used to the system during first sessions (n=3): Possibly use sensory habituation to the HMD (n=3), use free play to detect the child's preferences (n=1) Keep the child engaged: Make short sessions with breaks [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF] Keep child engaged (n=8): Alternate work and relaxation activities in XR (n=5), alternate work in XR and in real life (n=2); keep sessions short (n=1) (e.g., around 15mn) Include XR experiment as part of the global intervention: Make long-term studies [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Robins | Effects of Repeated Exposure to a Humanoid Robot on Children with Autism[END_REF] Include XR experiment as part of the global intervention (n=4): Have regular sessions every week (n=2); use XR at specific moments of the therapy (n=1), make long-term studies (n=1) Establish detailed procedures and provide training for the practitioners [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]

Mixed methods

Quantitative Evaluation

Assess the child's state before the experience [START_REF] Malihi | Short report: Evaluating the safety and usability of head-mounted virtual reality compared to monitor-displayed video for children with autism spectrum disorder[END_REF][START_REF] Maskey | A Randomised Controlled Feasibility Trial of Immersive Virtual Reality Treatment with Cognitive Behaviour Therapy for Specific Phobias in Young People with Autism Spectrum Disorder[END_REF] Assess initial state of the child (n=1): Conduct sensory profile Assess the child' experience: No consensus exists: Collect behavioral data [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], e.g., repetitive behaviors [START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF], interaction logs [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], eye-tracking [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Koirala | An Exploration of Using Virtual Reality to Assess the Sensory Abnormalities in Children with Autism Spectrum Disorder[END_REF]; collect physiological data [START_REF] Kuriakose | Design of a Physiology-Sensitive VR-Based Social Communication Platform for Children With Autism[END_REF]; use custom questionnaires [START_REF] Aruanno | HoloLearn: Wearable Mixed Reality for People with Neurodevelopmental Disorders (NDD)[END_REF][START_REF] Garzotto | Wearable Immersive Virtual Reality for Children with Disability: a Case Study[END_REF][START_REF] Garzotto | Magic Room: A Smart Space for Children with Neurodevelopmental Disorder[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF]; use common XR presence/anxiety questionnaires [START_REF] Malihi | Short report: Evaluating the safety and usability of head-mounted virtual reality compared to monitor-displayed video for children with autism spectrum disorder[END_REF][START_REF] Wallace | Sense of presence and atypical social judgments in immersive virtual environments: Responses of adolescents with Autism Spectrum Disorders[END_REF][START_REF] Wallace | Self-reported sense of presence and responses to social stimuli by adolescents with autism spectrum disorder in a collaborative virtual reality environment[END_REF]; use autism intervention questionnaires [START_REF] Malihi | Short report: Evaluating the safety and usability of head-mounted virtual reality compared to monitor-displayed video for children with autism spectrum disorder[END_REF][START_REF] Maskey | A Randomised Controlled Feasibility Trial of Immersive Virtual Reality Treatment with Cognitive Behaviour Therapy for Specific Phobias in Young People with Autism Spectrum Disorder[END_REF] Assess the child' experience and performance (n=2): Collect physiological data for stress measurement (e.g., biosensors, pressure sensors) (n=2), log observational data (n=2) Assess practioners' actions [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF], e.g., behavioral data, prospective adjustments Measure the ongoing progress [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]: Collect data from multiple measures

Qualitative Evaluation

Conduct behavioral observations: Film sessions [START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF] and take notes [START_REF] Brown | The case for conversation: a design research framework for participatory feedback from autistic children[END_REF] Conduct behavioral observations (n=2): film sessions (n=2), take notes (n=1) Conduct interviews, i.e., with caregivers/parents [START_REF] Pares | Achieving Dialogue with Children with Severe Autism in an Adaptive Multisensory Interaction: The "MEDIATE' Project[END_REF] and children (use videos, images, drawings if non-verbal, and closed questions, with screenshots, smileys if verbal) [START_REF] Spiel | When Empathy Is Not Enough: Assessing the Experiences of Autistic Children with Technologies[END_REF] Carry out interviews (n=1): if children can answer (n=1)

Design process

Participative design

Participative design

Use participative design [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Brosnan | Look up! Digital technologies for autistic people to support interaction and embodiment in the real world[END_REF][START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF][START_REF] Spiel | Agency of Autistic Children in Technology Research-A Critical Literature Review[END_REF]: Value the design experience of the child [START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF] Use participative design (n=5) Explicit all questions between stakeholders before to engage in collaboration [START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF] Inclusivity Consider the entire autism spectrum: Consider autism strengths and difficulties, include individuals requiring substantial support and adults [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF] Consider the entire autism spectrum (n=7): Include individuals requiring substantial support (n=5) and adults (n=2)

Equipment

Context-Dependent

Use ergonomic and affordable equipment, i.e., light [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF], portable, small [START_REF] Newbutt | Brief Report: A Pilot Study of the Use of a Virtual Reality Headset in Autism Populations[END_REF], non-tethered , affordable [START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF] Use ergonomic and affordable equipment (n=4): resistive (n=3), not cumbersome (n=2), portable (n=2), affordable by using HMDs (n=2), non-tethered or with long wires (n=1) Task-dependent

Use AR to aid in the generalization from virtual to the real world [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]

Use context

Setting Conduct experiments in ecological settings [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Parsons | Whose agenda? Who knows best? Whose voice?' Cocreating a technology research roadmap with autism stakeholders[END_REF] Conduct experiments in ecological settings (n=1) Age range

Age range: Possible from 13 years old for neurotypical people [START_REF] Gent | Are Virtual Reality Headsets Safe for Kids? livescience[END_REF] Age range: is task-dependent (n=7)

Information presentation

Little & Clear Information

Little information

Use little tasks to complete, e.g., unique goal per gaming session [START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF] Use little tasks to complete (n=4) Avoid stimuli when not task-relevant [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF][START_REF] Virole | Autisme et tablettes numériques[END_REF]: Use simplified graphics [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Tarantino | Immersive applications: what if users are in the autism spectrum?[END_REF] Avoid stimuli when not task-relevant: Use neutral environment (n=7), use simplified graphics (n=4) Display clear information [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]: foreground/background differentiation, clutter-free Make information clearly visible (n=1): Use clear foreground/background differentiation Minimize transitions: between game states (no sound, animations) [START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF] Minimize transitions (n=1): Gradually decrease appealing stimuli before to remove the HMD Avoid using metaphors [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF] Avoid using metaphors (n=4) Adaptation to the child's pace Make it possible to repeat or adjust information speed [START_REF] Tardif | Reducing Information's Speed Improves Verbal Cognition and Behavior in Autism: A 2-Cases Report[END_REF] Make it possible to repeat or adjust information speed (n=13) Use minimal prosody: no emotions [START_REF] Duris | Le robot Nao comme support relationnel et de dynamique groupale auprès d'enfants porteurs de troubles du spectre autistique[END_REF], little text/language [START_REF] Carlier | Empowering Children with ASD and Their Parents: Design of a Serious Game for Anxiety and Stress Reduction[END_REF]

Task-dependent

Socio-emotional abilities

Allow for rapid shifts between XR environments [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF] Use adjustable realistic naturalistic settings (n=5): to enhance the generalization of skills Use adjustable realistic naturalistic settings [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]: Support the adult-child relationship, give precise control over the virtual surroundings Train a variety of skills instead of specific skills [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF] Train balanced turn-taking [START_REF] Dechsling | Virtual reality and naturalistic developmental behavioral interventions for children with autism spectrum disorder[END_REF]: Use various contexts, visual prompting, rewards Others Realistic and non-realistic environments won't interest the same practitioners (n=1)

Avatars Representation

Use cartoonish non-human avatars [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Newbutt | Exploring Communication and Representation of the Self in a Virtual World by Young People with Autism[END_REF] Use cartoonish non-human avatars (n=1) Make XR avatars customizable [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF][START_REF] Newbutt | Exploring Communication and Representation of the Self in a Virtual World by Young People with Autism[END_REF] Only hear a XR avatar instead of both hearing and seeing it [START_REF] Newbutt | Exploring Communication and Representation of the Self in a Virtual World by Young People with Autism[END_REF] Position the avatars at real-world height [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]

Use

Use avatars as tutors for children [START_REF] Bozgeyikli | A Survey on Virtual Reality for Individuals with Autism Spectrum Disorder: Design Considerations[END_REF]