Philip Heslop
email: philip.heslop@ncl.ac.uk

Anne Preston
email: anne.preston@ncl.ac.uk

Ahmed Kharrufa
email: ahmed.kharrufa@ncl.ac.uk

Madeline Balaam
email: madeline.ballam@ncl.ac.uk

David Leat
email: david.leat@ncl.ac.uk

Patrick Olivier
email: patrick.olivier@ncl.ac.uk

Evaluating Digital Tabletop Collaborative Writing in the Classroom

Keywords: Digital Tabletops, collaborative learning, multi-touch, 1

de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Dig ital tabletops have been described as a collaborative tool that can impact educational processes in the classroom [START_REF] Dillenbourg | Interactive tabletops in education[END_REF][START_REF] Kharrufa | Exploring the requirements of tabletop interfaces for education[END_REF]. They are considered a med iu m for social learning [START_REF] Dillenbourg | Interactive tabletops in education[END_REF], and have potential to foster a more co llaborative, g roup-based approach to learning, such as students being exposed to different v iewpoints (and possible solutions), developing critical thinking skills and a more nuanced understanding [START_REF] Piaget | The language and thought of the child[END_REF]. visuospatial qualities of the tabletop to support learning about fractions. Students spatially manipulate tiles to fill a canvas to visually represent fractions. Digital Mysteries [START_REF] Kharrufa | Digital Mysteries: Designing for Learning at the Tabletop[END_REF][START_REF] Kharrufa | Learning through reflection at the tabletop: A case study with digital mysteries[END_REF][START_REF] Kharrufa | Tab les in the Wild : Lessons Learned fro m a Large-Scale Multi-Tabletop Deployment[END_REF][START_REF] Kharrufa | Exploring the requirements of tabletop interfaces for education[END_REF] also takes advantage of the visuospatial qualities of the digital tabletop, allowing students to resize, group and connect informat ion to help the groups collaboratively formu late an answer to a question without a distinct "correct" answer. The Co llocated Collaborative Writing application (CCW) [START_REF] Heslop | Learning Extended Writ ing : Designing for Ch ildren ' s Collaboration[END_REF] builds on these design principles, producing a tool for learning extended writ ing collaboratively. In general, the designs have been found to successfully support collaborative learning interactions, with evaluations showing:

1. Designing for the dig ital tabletop is mo re than a remediation o f content; it requires specific design in order to fully utilise their affordances [START_REF] Dillenbourg | Interactive tabletops in education[END_REF][START_REF] Kharrufa | Digital Mysteries: Designing for Learning at the Tabletop[END_REF][START_REF] Rick | Fro m DigiQuilt to Dig iTile: Adapting educational technology to a multi-touch table[END_REF]. 2. Externalisation of thin king can be facilitated by the digital tabletop through visuospatial representations [START_REF] Heslop | Learning Extended Writ ing : Designing for Ch ildren ' s Collaboration[END_REF][START_REF] Kharrufa | Digital Mysteries: Designing for Learning at the Tabletop[END_REF]. 3. Applications can regulate learning by splitting tasks into stages and through scaffolding [START_REF] Heslop | Learning Extended Writ ing : Designing for Ch ildren ' s Collaboration[END_REF][START_REF] Kharrufa | Digital Mysteries: Designing for Learning at the Tabletop[END_REF]. These applications have shown learning improvements for single group s but have not been evaluated in a whole-class setting.

Increasingly, work has been published describing the deployment of mult iple ta bletops into learning contexts in the wild. Descriptions of classroom deployments of mu ltip le tabletops have shown that there are significant differences and difficulties not found in single tabletop deployments [START_REF] Kharrufa | Tab les in the Wild : Lessons Learned fro m a Large-Scale Multi-Tabletop Deployment[END_REF] and even in mu lti-tabletop scenarios that are not integrated into an authentic curriculum setting [START_REF] Kharrufa | Extending tabletop application design to the classroom[END_REF]. This requires:  Sessions take place in an ordinary classroom based in a school.  Multiple simultaneous groups working on multiple digital tabletops.  Supervision by the teacher who usually teaches the lesson to the students.  Teacher created content for the sessions based on their teaching goals.  Integration of the technology into teachers' lesson plans and tying the activity to specific learning goals.

The findings have common ly focussed on the design of technological strategies that can support the teacher's management and orchestration of the class [START_REF] Martinez-Maldonado | Orchestrating a Multi-tabletop Classroom : Fro m Activity Design to Enact ment and Reflection[END_REF]. It is clear fro m these earlier "in the wild" mu lti-tabletop deploy ments [START_REF] Kharrufa | Extending tabletop application design to the classroom[END_REF][START_REF] Kharrufa | Tab les in the Wild : Lessons Learned fro m a Large-Scale Multi-Tabletop Deployment[END_REF] that the precursor to an adequate evaluation of the impact of the tabletops, is for teachers to embrace the technology as a tool they can use effectively to support learning by integrating it into lesson plans.

In this paper, we contribute a learn ing focussed evaluation of a mu lti-tabletop deployment in a classroom supervised by a teacher during normal lesson time. In so doing, we 1) focus primarily on the nature and quality of one group's collaboration through the students' commun icative interactions with the technology and each other, 2) track the g roup's development over t ime as part of scheme of wo rk planned by the teacher, and 3) use classroom level data streams to show how this is indicative of the class as a whole. I.e. using the group as the unit of analysis to generalise the collab orative behaviours occurring in the classroom [START_REF] Roschelle | The construction of shared knowledge in collaborative problem solving[END_REF].

Collocated Collaborative Writing

Collocated Collaborative Writing (CCW) [START_REF] Heslop | Learning Extended Writ ing : Designing for Ch ildren ' s Collaboration[END_REF] is an application designed to facilitate the learning of extended writ ing in s mall groups by explo iting the affordances of dig ital tabletops. Extended Writing can be characterised as any writing using specialised vocabulary and a formal structure. Planning is an essential skill in producing high level structured writ ing [START_REF] Kirkpatrick | Planning text structure as a way to improve students' writ ing fro m sources in the compare-contrast genre[END_REF][START_REF] De La Paz | Exp licit ly teaching strategies, skills, and knowledge: Writing instruction in middle school classrooms[END_REF] and good quality plans tend to be well structured (i.e. include well-connected paragraphs), on topic (i.e. not generic or abstract) and lead to higher quality final documents [START_REF] Bern Inger | Assessment of planning, translating, and revising in junior high writers[END_REF]. Writ ing Frames [START_REF] Lewis | Writing Frames. Reading, UK Read[END_REF] are a paper-based scaffold to support extended writ ing. Using specific genres, the method provides partial plan-like structures to be completed by students. Fig. 1 shows the current CCW interface.

The task is split into stages , and students themselves decide (with a decision point) when to attempt to progress. If certain criteria are not met, then the students are given scaffolded instructions to help them towards completing the current stage.

The four stages are: 1) Exami ne Evi dencestudents read through the evidence slips.

2) Create (Named) Paragraphsstudents create new paragraphs and give appropriate namesa min imu m of four paragraphs must be made to progress. 3) Connect Paragr aphsto progress all paragraphs must be connected and 4) Us e Evi dence: where evidence slips are inserted into paragraphsto progress, each paragraph must have a minimum of three evidence points, either from slips or created by students.

CCW is designed on principles of collaborative learning [START_REF] Vygotsky | Mind in Society[END_REF], incorporating ideas fro m d istributed cognition with focus on the use of space and the manipulat ion of representations [START_REF] Dillenbourg | Distributing cognition over humans and mach ines[END_REF][START_REF] Kirsh | The intelligent use of space[END_REF][START_REF] Norman | Things that make us smart[END_REF][START_REF] Rogers | Distributed cognition: an alternative framework for analysing and explaining collaborative working[END_REF][START_REF] Zhang | Distributed cognition , representation , and affordance[END_REF]. It also includes teaching methods such as scaffolding [START_REF] Wood | The ro le of tutoring in problem solving[END_REF][START_REF] Wood | Vygotsky, Tutoring and Learn ing[END_REF] to co mplement and support the scaffolding supplied by teachers. The two main interaction design concepts leveraged to turn writing into a collaborative p rocess are: 1) the use of a visuospatial design allows fo r representation and communication of ideas, i.e. paragraphs, evidence, and connectors are created as visual represent ations that can be manipulated by mult iple users allowing visual externalisation and communicat ion of ideas.

2) The introduction of decision points throughout the process: between stages, creation of a paragraph, and adding connections. Such decision points help regulate the progress and prompt collaborative discourse, i.e. Proposals [START_REF] Barron | When Smart Groups Fail[END_REF]. The interface is cumulative; that is, no functionality is lost between stages and additional functionality works on the existing state. Accordingly, the decisions made to reach the current representation can be determined by ob serving the current state.

The iterative design process of CCW [START_REF] Heslop | Learning Extended Writ ing : Designing for Ch ildren ' s Collaboration[END_REF] was based on single group studies. Previous integration into the classroom [START_REF] Kharrufa | Tab les in the Wild : Lessons Learned fro m a Large-Scale Multi-Tabletop Deployment[END_REF] highlighted significant differences between the requirements for a single group and the requirements of a classroom [START_REF] Kharrufa | Extending tabletop application design to the classroom[END_REF][START_REF] Kharrufa | Tab les in the Wild : Lessons Learned fro m a Large-Scale Multi-Tabletop Deployment[END_REF]. The study was designed to investigate the relationship between students and the technology through their co llaborative behaviours , and that between the teacher and the technology through her feedback and lesson plans. It was conducted over 4 sessions across a half term (6 weeks) in a UK secondary school classroom. The classroom was equipped with 8 smart tables, allo wing 8 groups of 3-4 students to participate -30 students in total. The students were native English speakers of mixed ab ility, studying English in Year 8 (aged 13-14, key stage 3). Each lesson was planned and facilitated by the class's usual English teacher, who also produced the session content. Sessions were scheduled to fit in with the existing timetable. The teacher met with the research team to d iscuss and improve the des ign before the study and had completed a collaborative writ ing task using CCW. She designed lesson plans to incorporate the technology into her teaching goals. 2-3 Researchers were present at each session, and sessions were filmed with a classroom camera and a single group camera (Figure 2). Before each CCW session, the students completed a collaborative exercise, either Dig ital Mysteries [START_REF] Kharrufa | Digital Mysteries: Designing for Learning at the Tabletop[END_REF] (first 3 sessions) or a classroom debate (final session). The "in the wild" context also had significant practical ramifications, including:

Study Protocol

 The classroom was in use for other lessons during the day, mean ing the experimental setup (i.e. all tables and recording equipment) had to be deployed before each session and dismantled after, leaving the classroom in its previous configuration.  Schedule restrictions meant that this had to be completed in less than 1 hour.  The space available in the classroom did not allow a camera per table.

Data and Analysis

The deployment gathered data from several sources , providing multip le lenses through which to view the deployment using a mixed -methods [START_REF] Creswell | Designing and Conducting Mixed Methods Research[END_REF] approach. A classroom camera (Figure 2a) captured each session, the digital tabletops recorded interaction logs, the teacher recorded lesson plans and reflections for each session, and co llaborative document p lans and individual written work were generated and assessed by the teacher. A detailed overview o f learn ing interactions can be derived fro m an analysis of the single group video (Figure 2b) and audio-recording of each session (n=4). When synchronised with interaction log data (i.e. creation, man ipulation and deletion of visuospatial elements, decisions made and text generated etc.), we were able to provide a detailed view of how learning was s caffolded by CCW.

This paper provides an in-depth, learning-focused analysis of a single group interacting with CCW over four sessions. Using the group as a unit of analysis [START_REF] Barron | When Smart Groups Fail[END_REF] [28], we tracked development over time as part of scheme of work planned by the teacher. The situated nature of the deployment (i.e. in real classroom, with space and time constraints) restricted data collection opportunities (i.e. video per table) for detailed mu ltiple group analysis . Ho wever, other data streams, such as interaction logs, classroom camera and teacher plans and reflections , provided a contextual background.

Fig. 3. Expanded Bartu Decision M aking Framework

In order to be able to map a group's learning interactions to key design features of CCW (externalisation and communicat ion of thinking through visuospatial representations) we utilised an "event-driven" approach to analysis [START_REF] Rogers | HCI Theory : Classical, Modern and Contemporary[END_REF]. This allo wed us to evaluate, according to distributed cognition, how cognitive processes promoted by CCW were co-ordinated across time, and where events in one session impacted or transformed in later sessions [START_REF] Hollan | Distributed cognition: toward a new foundation for humancomputer interaction research[END_REF].

Bartu [START_REF] Bartu | Decisions and decision making in the Istanbul Exp loratory Pract ice experience[END_REF] uses the concept of Proposals to examine group decision -making processes. Proposals fall with in a class of speech acts (that can be non -verbal) which are used to make 'suggestions', in order to encourage listener(s) to carry out some future course of action [START_REF] Searle | Speech acts: An essay in the philosophy of language[END_REF]. They are performed according to how the speaker designs an action (e.g. as a question, exclamation, or imperative) [START_REF] Markee | Conversation Analysis[END_REF]. The concept of Proposals maps to the design of CCW through decision points (and visuospatial representations).

Based on Bartu's notion of Proposals we developed an organisation al framework to describe the decision-making process incorporating CCW (see Fig. 3 ). A decision-making episode is initiated through a Proposal. Then a number of different combinations of interactional moves are possible through decision -making 'speech acts'. These moves, in conjunction with interactions with CCW, allo w the speakers to implement a decision scaffolded by CCW. Analysis concentrated on the mu ltimodal interactions at a micro-level, including verbal and non-verbal behaviour that formed the structure of the collaboration, focused on the co-construction of Dec isions and use of Proposals to initiate these decision-making processes (i.e. CCW decision points).

Methods from Discourse Analysis (DA) [START_REF] Sinclair | Towards an analysis of discourse: The Eng lish used by teachers and pupils[END_REF] were used to facilitate a systematic and structured way to describe and analyse the organisation of group interactions. This is carried out fro m the perspective of distribution, co-ordination and impact of cognitive processes over time and the consequences of the design goal of collaborative decision making, i.e. "explo re the organisation of social interaction through dis course as coherent in organisation and content and enable people to construct meaning in social contexts" [START_REF] Coyle | Discourse Analysis[END_REF]. As such, our analysis examined language and sense-making practices as they were co-constructed across mult iple modes of co mmunicat ion including s peech, gesture and other contextual phenomena [START_REF] Scollon | Mu ltimodal discourse analysis as the confluence of discourse and technology[END_REF]. The DA co mprised of two phases. First, decision-making episodes were identified fro m the video data (independently by two researchers, followed by a consensus). These were marked as stretches of interaction made up of the init iation of a Proposal (as suggested by Barron [START_REF] Barron | When Smart Groups Fail[END_REF]), subsequent discussion around this Proposal that ended with a decision (see Figure 2). Secondly, in each episode, the focus of the analysis was on the incremental process of reaching a decision and imp lementing it (scaffolded by CCW) using Proposals. A double coding of interactional behaviours was performed; t wo researchers worked first independently, then together to reach agreement about the coding of decision -making 'speech acts' within the episode.

Results

This section provides a summary o f results based on the qualitative and quantitative analysis across 3 data sets: single group video and audio, teacher notes and interaction logs. Observation of decision-making (as a product of interactions with CCW and group members) provide quantitative data concerning use of turn -taking and Proposals. These results were used sequentially -they provided a starting point for looking in more detail at the nature and quality of the decision -making as a collaborative process mediated by CCW. When turns are used as a way of evaluating participation, the data suggests that Session 2 produced the lo west rate of participation in the tabletop activity. The highest number of turns, and increased participation was observed in Session 3, slightly decreasing in Sessions 4 and 5. This first phase led the init iation of specific questions concerning the relationship between turns of talk (indicating levels of part icipation), Proposals (i.e. those occurring away fro m the table, mediated direct ly with CCW and fro m facilitators), and the nature and quality of activity in the interactional space between the initiation of a Proposal and decision-making.

The following sections provide the results for the qualitative analysis of the group interactions with CCW, together with results from the analysis of the teacher's notes and interaction logs. These data were correlated according to a Convergent Parallel Mixed Methods Design [START_REF] Creswell | Designing and Conducting Mixed Methods Research[END_REF]. For each session, an overview of the focus of the lesson is presented, follo wed by an excerpt provid ing a detailed micro -view of the nature and quality of interactions with CCW, typical o f that particu lar stage of development of the group in the whole-class deployment. A short commentary of the transcribed ep isode is then provided which serves as a qualitative account.

Session 1 -Midsummer Night's Dream

The students worked on writ ing a persuasive document answering the question "Which character is the most powerful?" (~20 mins) based on a Digital Mystery they had completed in the same session (~45 mins). The teacher introduced the session, with topic related notes on the whiteboard, e.g. main characters, groups of characters and brief plot synopsis. The episode comes from the first 'reading slips' stage. The episode begins with a Proposal (1) from M1 who initiates joint attention to a slip. F2 then rejects this Proposal, leading to a series of contributing turns, where F2s Proposal (2) to 'trash' existing slips is accepted by the group, until M2's Proposal [START_REF] Bern Inger | Assessment of planning, translating, and revising in junior high writers[END_REF], which is accepted, and activity continues until the Facilitator joins the group to make Proposal (4). This is accepted by each group member. There are 4 Proposals made around and through CCW, but there is no Finalisation to Proposal (1) (the initiation of the activity). Rather, the Facilitator refocuses attention on the task requirements.

Commentary: Despite the high nu mber of turns (Table 1), suggesting a high level of participation, the nature of the interaction in terms of decision making processes (i.e. Proposals) suggests low quality. The episode shows a lack of focus on task demands, evidenced by the intervention by the facilitator and in the quality of the collaboration.

Although the students actively watch each other and co-ordinate their efforts, this is not integrated with CCW. Proposals and decisions are made by individuals and are superficial. Those linked to CCW are initiated without prior discussion.

Despite the lack of Finalisation, this episode demonstrates how the nature of collab oration with and around the table is lin ked to a mutual orientation to the task facilitated by CCW; students' joint attention to each other's talk and actions is highly coordinated. Students make use of the affordances of the table: demonstrating an understanding that that slips can be selected, read and, if required, trashed.

Classroom Level:

The interaction logs of other tables in the classroom show that no groups completed the task, mostly stopping at the paragraph construction stage. Ge nerally, task-provided ev idence was seldom used with g roups writ ing their own outline items. During the session, the teacher moved between the groups and observed that paragraphs were being named abstractly rather than on-topic. She reflected on this in her notes, and decided to incorporate an explanation in the plan for the next session.

Session 2 -Midsummer Night's Dream -Part 2

The session, exp loring the same question, took around 25 minutes. The teacher again began with a topic su but also included an exp lanation of good paragraph naming strategies (i.e. on-topic). The teacher reminded the class of this during the paragraph creation phase. Two analysed episodes are presented, connected by the Initiat ion of Activity (Proposal 1) in Part 1 and the Finalisation linked to that in itiation at the end of Part 2. 1) and the students move to the next stage -a Finalisation point.

Commentary: Table 1 suggests a lower rate of part icipation in terms of turns, ho wever there was a relative increase in Proposals (from facilitators, students and CCW), suggesting a closer task focus from the students and the teacher.

The episodes, as representative of broad patterns of interaction in Session 2, demonstrate an improvement in the quality of collaboration fro m the first session. Coordinated mu ltimodal interaction shows behaviours focussed on specific goals, sca ffolded more specifically here by CCW. However, similar Session 1, there is litt le verbalisation, so actions on the table are not considered by the group before being executed. There is also a continuation of similarly ind ividualised action when M1 directs the connecting of paragraphs to F1. Proposals are generated by students and CCW, co-ordinated to achieve specific interactional goals. CCW and the teacher p lay a more concrete role in scaffolding decision-making by generating Proposals and mediating those put forward by the group.

Classroom Level : The logs show that groups changed their paragraph naming strategy after the mid-session reminder and all groups finished the task although some rushed rather than create good answers (particularly with regard to connections and use of evidence). Again, groups did not use the provided evidence, preferring to write their own. Rather than use the generated plans for a text generation exercise, the teacher created a model answer for the students to look at in the next session.

Session 3 -Greek Mythology

Before the session, the teacher asked students to "assess" her previous session answer.

In this session (~25 mins), the aim was to create a persuasive document about Greek Mythology. The teacher provided a summary on the board, and the context -writ ing a Proposal for a museum display. Three episodes are analysed showing how the organisation of the decision-making processes around CCW (based on Proposals) are not isolated events but evolve incrementally, intertwined with previous decisions . 2)). In subsequent turns of this decision-making process, there are a number of contributions [START_REF] Dillenbourg | Distributing cognition over humans and mach ines[END_REF] and Rejections [START_REF] Bern Inger | Assessment of planning, translating, and revising in junior high writers[END_REF] until Proposal ( 2) is accepted by F2. A further Proposal ( 3) is also rejected in this same turn. This complex sequence (which does not reach complete Finalisation) shows specific joint attention to the 'content' of Proposal ( 1): There is a collaborative orientation to correct terminology where it is shown to be an explicit part of the decision-making process.

Commentary:

The session had the highest rate of participation in terms of turns, and also the highest number o f Proposals, both from the students and CCW. However, the Proposals provided by the facilitator decreased. The nature and quality of the decision making process increased, as demonstrated in the representative episode.

Students continue to demonstrate joint attention to the task as they watch the text appearing on the table. Central to this change is the occurrence of talk prio r to final isation of decision-making which is imp lemented using the table. The focus on the content of the paragraphs shows how the Proposals are used in the development of finalisation rather than to initiate it -indicating a change in the distribution of who is leading the process and the role of CCW. These episodes demonstrate a change in terms of the development of decision-making processes from Sessions 1 and 2.

Classroom level : Logs show that all groups continued in the "on topic" paragraph naming strategy, but created more topics in less time. All groups created plans that were assessed by the teacher. The teacher reported that writing a "proposal", rather than a "straight forward" persuasive document, was "too much" for some groups, and decided to go over the "basics" of persuasive writing and choose an easier context.

Session 4 -Sport vs. Library

In this session the students were working on writing a persuasive argument to decide between funding for a library or new sports facilit ies at the school (~25 mins). They had previously held a classroom debate, including a paper based exercise involving reading and organising evidence and producing a structure they could use to design their document. (Interestingly, the structures mirrored the CCW process without prompting). The teacher provided a short reminder of persuasive texts . The episode opens with an Initiation of Activity by F2 to add content to a paragraph 'For L ibrary'. In doing so, the group's joint attention is on F2 as she consults her notes then drags a slip into the Library Paragraph. This Proposal ( 1) is followed by a similar action by F1 who drags another slip to the same box. In F1's turn there is no dialogue and no other group member accepts nor rejects this Proposal.

F2 next proposes a new action (Proposal (3)) to write something in the Library Paragraph (rather than only drag existing slips). Eight overlapping Proposals then follow and are accepted by 1) M1 who is the 'scribe' on this occasion and notes them down via the keyboard 2) non-verbal means such as nodding and 3) echoing and building on each other's turns (Proposals). The activity ends when a group display of joint attention to M1 who types the final point into the paragraph, which leads to the initiation of a new, linked activity ("what could be used against the library?").

Commentary: Table 1 indicates a high rate of participation in terms of turns (co mpared to first and second sessions). The number of Proposals remains similar to session 3, however CCW is being used more to implement and scaffold decisions.

As one of a number of similar ep isodes observed in Session 4, this episode shows how the collaborative nature of decision-making processes with and around CCW has developed across the sessions; culminating in co-ord inated, productive and high quality mu ltimodal interaction. The students actively watch and listen to each other and collaboration contains both individualised and collective Proposals. CCW is used to both initiate Proposals by members of the group (dragging and dropping slips into the paragraph) and support the development of verbal Proposals linked to content which is discussed prior to being added. High quality collaborat ion is not defined by one decision-making structure but a merging of events built up over the sessions.

Classroom Level : All groups completed the task, creat ing plans that were used as the basis for an indiv idual writing ho mework exercise, assessed by the teacher. The teacher was encouraged by the final documents, reporting that all students showed improvements.

Discussion

In this study, we used a single group analysis to obtain a deep understanding of activity at the tabletop throughout a classroom deployment, but also used further classroom data streams to provide a whole class context. We were able to integrate the technology into the analysis of the group's discourse due to specific design elements of CCW designed to generate Proposals (i.e. decision points), and by adapting Bartu's model ( Fig. 3) to recognise these Proposals alongside those generated through discourse. The mu lti-tabletop classroom deploy ment has enabled evaluation of CCW as a learning tool (evidenced through the students' changing relationship with CCW), as well as provided insights into the teacher's integral role in integrating technology in the clas sroom (evidenced through the teacher's reflection and adaptation of lesson plans).

Student's Relationship with CCW

Students had a changing relationship with CCW, which centred on Proposals, and their talk developed across the sessions. The group level analysis allowed us to view the different kinds of collaborative events driving the learning in specific interactions around decision-making p rocesses over time in terms of student, facilitators and CCW. Participants' use of specific design elements, included to elicit collaborative behaviour such as decision points and visuospatial elements, were also developed.

In the first two sessions, facilitators were the prime source of Proposals and CCW was not central to the students' talk nor to their activity. CCW Proposals (i.e. through decision points) were used superficially, in an individualised manner and with litt le follow-on develop ment. In these initial sessions, paragraphs were created with a bstract names (until the teacher's classroom intervention) and task-provided evidence was seldom used. Rather, students made their own points for the paragraphs.

In Session 3, group Proposals were offered and discussed while CCW was used to facilitate the transition of ideas to the p lan as a collaborative effort. CCW provided scaffolding via Proposals (decision points etc.) that were attended to by the students. Eventually, CCW could be seen to begin to 'fade' [START_REF] Wood | Vygotsky, Tutoring and Learn ing[END_REF], with more talk happening offtable before using CCW (to confirm "correctness" before proceeding). Paragraphs were created with on-topic themes, although paragraph connection was still naive. Evidence, was now being used extensively and correctly in persuasive arguments.

In Session 4, Proposals largely came fro m the group, while CCW mainly i mplemented shared decision making, i.e. interactional focus was more on the students than the table . Students decided what they wanted to do via talk before imp lementing their decision on the table. In fact, so me CCW design elements (i.e. pro mpting for group agreement) began to hinder students' collaboration. The scaffolding provided by CCW "faded", but the applicat ion did not recognise this and still provided the same mechanis ms. Task-provided evidence was used in conjunction with the students' points rather than an all or nothing strategy fro m previous sess ions, i.e. to corroborate persuasive arguments being generated by the students.

As this study has evidenced, the identified changing relat ionship between students and CCW has clear generalizab le consequences on application design. They necess itate that the application design should be flexib le enough to allow for such variance in usage. The application should therefore allow for controlling (whether automat ically or even manually by the teacher o r students) the level of scaffolding, and correspondingly fading, provided. Otherwise, the application's role may shift fro m being su pportive of the task to being a burden. This variable scaffolding could also be a tool for differentiation across groups of differing abilities across the classroom.

Integration into the Classroom

A key factor for the impact of the study is how the technology was integrated into the classroom. The teacher is vital in this process, as they control the teaching goals and orchestrate the classroom based on their familiarity with the needs of the students.

Looking at the additional data streams (classroom camera, interaction logs and the teacher's lesson plans and notes), we can monitor the bigger picture of the classroom over the study. They show how the teacher adapted her plans, during or after the sessions, to get the best out of the technology. She used classroom introductions and interventions to provide background informat ion and suggest ed strategies for successful persuasive writing (such as on-topic paragraphs). She adapted her assess ment approach when it became clear that the students would not comp lete the task (by supplying a model answer fo r students to "mark" rather than writ ing their own). She also appropriated the sessions for use beyond the persuasive writ ing task, i.e. as a method for bringing out the underlying theme of "power" from the students.

As a class, the data show that the students benefited from the teacher's adaptive, student-centred teaching approach. The work produced, such as creating and connecting paragraphs and using evidence, increased in quality, but not always linearly. E.g. in Session 3, some groups had lost a focus on persuasive writ ing, and relied on existing evidence provided by the teacher via CCW. Session 4, saw a move to more persuasive-orientated, student-generated content. In summary, the technology gave the teacher mo re power to fu lfil her teaching goals and benefit the class, rather than replacing some or all of her activities.

The in-the wild nature of the study places a premise on the data collection process. Time and space constraints do not allow for every group to be individually recorded, and so detailed findings fro m a single group must be co mbined with higher level data fro m the classroom level. Examination of interaction logs, classroom camera and teacher notes and reflection allow for general patterns to be identified that indicate that the class as a whole followed a similar pattern to the single group. However, in an ideal world, full data on all groups would yield a more comprehensive analysis.

Despite such limitations, these observations were only possible due to our "in the wild", classroom based approach. Two important design elements of the application allo wed the teacher to make the required observations to adapt her strategy during the sessions (and across the study as a whole):

1. The externalization concepts incorporated into the design and cumulative representation aspects of the design raised the teacher's awareness of the students' tendency to use superficial paragraph names and lack of persuasive line of argu ment, rather than waiting until a post-session outcome assessment.

2. The flexib ility of the design enabled the teacher to imp lement these changes in strategy in the introduction or mid-session classroom announcements, such as assessing group-made plans before individual writ ing assessment, providing a sample document for students to consider, or focusing on particular task demand.

Conclusion & Future Work

We presented an "in the wild" evaluation of a Collocated Collaborative Writing a pplication on mult iple dig ital tabletops. We used video data integrated with interaction logs to gain a detailed mo ment to mo ment insight into one group's learning. We use d a classroom camera, interaction logs and teacher plans and reflection to build a context-specific analysis.

We observed that the students' collaboration progressed from relying on teacher and facilitator Proposals, through using CCW's scaffolding, to the point where CCW became simply a planning and assisting tool where the scaffolding aspect faded. We found that the visibility of the state, made possible through the cumulat ive nature of the task, along with the flexib ility of d ividing the task into stages, enabled the teacher to adapt her lesson plans over the course of the deployment. Moreover, the ro le of the teacher as classroom orchestrator in conjunction with the technology was vital, requiring a positive relationship with the technology with regard to her teaching goals.

This study has worked towards identifying and understanding more about the nature and quality of learning through CCW in an 'in the wild' classroom deployment. It discussed the deployment of the application as part of the 'machinery' o f everyday classroom life. In doing so, the study's mixed method approach allowed us to build up an understanding of how the relationship between the students and technology, as well as the teacher and technology, changed over time in the everyday life o f the classroom. So me of these behaviours and decisions may pro mpt for new approaches to teaching and learning (for examp le, new ways of looking at group collaboration alongside individual work). Yet they also demonstrate how the teacher can still main-tain existing practices in terms of classroom orchestration, i.e. technologies can be normalised into the classroom.

This change in relationship between students and technology, which was only observable because of the longitudinal, "in the wild" nature of our study, is not specific to CCW. It demonstrates that any collaborative learning technology targeting the classroom should be flexible enough to take account of such change in relat ionship, and make such changes clearly visible to the teacher. The design should provide visib ility of both task-level details (paragraph names for example), and also higher level usage patterns (such as the overall level of interaction with the technology and communication amongst the group). By allowing such visibility of use, co mbined with flexib ility in imp lementing teacher's changes in strategy (whether 'on the fly' in-session, or between sessions), it is possible to have the positive relat ionship with the technology, as shown in this study, which is key to technology adoption in the classroom. This would not have been possible in a lab-based or single-group deployment.

This visible, flexib le teacher o rientated design approach raises possibilities for further investigation into how such flexibility can be further supported by applications -not only how to support (and design for) different ability levels, but make scaffo lding dynamic or adaptive as this relationship changes. This initiated classroom-sensitive questions such as: How much influence should the teacher have over these adapt ations? Are they part of the initial lesson plan, or can they be tweaked on the fly? Can orchestration tools be developed that allo w teachers to monitor and adapt tasks to enable dynamic differentiation?

Fig. 1 .

 1 Fig. 1. : CCW Interface: 1. Evidence Palette 2. Evidence Slips 3. Paragraphs 4. Connection CCW builds on Writing Frames and focuses on persuasive writ ing (one of the mo re difficult genres). The genre requires the creation of a persuasive argument across several paragraphs, including supporting evidence and consideration of alternative interpretations. Un like the paper based Writ ing Frames, CCW allows the document structure to be changed dynamically.

Figure 2 :

 2 Figure 2: a) Classroom Camera b) S ingle Group Camera

  Participants are: M1 = Male 1, M2 = Male 2, F1 = Female 1, F2 = Female 2, T = Table, G = Group and Fac = Facilitator. [ ] = Overlapping speech and (( )) Describes non-verbal activity. Encoding is P = Proposal, C = Contribution A = Acceptance, R = Rejection, Cl = Clarification, PP = Postponing, I = Initiation of Activity and F= Finalisation.

F2 for the libraryF1&M 1 (

 1 you could have ((reads notes she has on lap)) P1 (look at a distance at the page of notes that F2 is reading)) C F2 ((Selects Slip and drags to Library Paragraph)) P1 F1 ((Selects another Slip and drags to Library Paragraph)) P2/A2 F2 I knew all of them just put like number three put that in then write something. to type into the library paragraph)) A3 M2 like where we can allow children to study hard for upcoming [exams P4 M1 [expand their learning [skills P5 M2 [expand their knowledge their knowledge on P6 G ((all watch as M 1 adds the additional text to the paragraph)) A4like i.e. English, M aths. P9 M1 don't know if they need special case ((M 1 ((types final point into paragraph)) CL/R/F G [((watch M 1 as he types final point)) C M1 What could be used against the library? I/P1

Table 1 .

 1 Table 1 displays the number of Proposals identified in each session. Proposals are categorised and quantified (by facilitator, CCW and group), and turn taking is also quantified showing the number of speech acts overall. : Proposals and Turns by videoed group per session

	S ession Number

Table 2 .

 2 Episode from Session 1: M idsummer Night's Dream

	M1 right Oberon [((tries to drag and create slip but nothing is selected))	I & P1
	G	[((all watch as M 1 tries to create a slip))	C
	F2	((selects a slip)) that's not the right one put it in the trash. ((moves slip to	R & P 2
		trash))
	G	[((all watch as F1 selects and moves slip to trash))	C & A2
	M1 [in the trash]	C
	F2	((continues to select slips and trash them, all continue to watch this activi-	C
		ty))
	M2 ((selects slip and moves towards trash)) which would you like	C & P3
	F2	that one	A3

M2 [((moves selected slip to the centre of the table)) C Fac [((Fac moves to the group)) … because you guys just spent half an hour reading these slides you don't need to read them all again so I'll move you onto the next stage. ((closes this part of the task and moves the group to the next stage)) now we're going to think about what paragraphs you want if you look at the instructions it will tell you how… P4 G ((read the instructions on screen)) A4

Table 3 .

 3 Episode

	I & P1

from Session 2: M idsummer Night's Dream: Part 1 M1 next stage ((uses interface to bring up options for move to next stage))

In Part 1, M1 initiates the main activity by proposing a move to the next stage in CCW (Paragraph Creation). After Clarification from CCW, all display an Acceptance of M1's Proposal, indicating a consensus. CCW warns that there are not enough connections (Proposal 2). In Part 2, the decision-making process is expanded to take into consideration this applicationbased Initiation of Activity.

Table 4 .

 4 Episode from Session 2: M idsummer Night's Dream: Part 2

	G [((all read the information displayed))	C
	M1 [more paragraphs oh then you need to do it	C/P2
	G [((all confirm that they have read the message and move back to the on-going	C
		activity of connecting paragraphs))
	F1 ((selects previously written text which has not been connected and drags to	A2
		paragraph))
	T	((displays the two paragraphs which the students wish to link and connection	P3
		dialogue))

Table 5 .

 5 Episode

		from Session 3: Greek M ythology: Part 1
	F2 right monsters ((holds keyboard and prepare to type))	I/P1
	M1 no gods		R1/ P2
	M2 just put gods		C/R1
	F2 goddesses or gods	R1/ P3
	M1 Gods		C
	M2 gods and then goddesses.	C
	F2 ((types "gods" as Paragraph title))	A2
	G	[((all watch the interface as F2 types in the text))	C
	M1 [just put gods and goddesses.]	C/R1/P
			4

F2 [((confirms Paragraph Creation)) no it'll work better this way, because it means then we'll have more excuse to do more writing.

R3/A2/F

Part 1 opens with a Proposal (1) from F2, who is holding the keyboard and acting as 'scribe' to initiate the activity of creating a paragraph. The title of the paragraph (rather than the creation) is met with a Rejection from M1 who proposes an alternative (Proposal (

Table 6 .

 6 Episode

		from Session 3: Greek M ythology: Part 2
	F1 ((Selects Creates Paragraph))	P1
	F2 ((types "Goddesses" as Paragraph title))	C
	G	((all watch the interface as F2 types in the text))	C
	M2 yes, it's actually two Ds you can just use the arrow keys.	PP/P2
	M1 I'm sure it's not two Ds.	C/R2
	F2 It's not two Ds.	C/R2
	…discussion as to the spelling of goddesses continues over a number of turns…until	A1/F
	group creates new paragraph
	Part 2 shows similar decision-making processes based around the content of paragraph head-
	ings. This time, the spelling of the title is proposed (Proposal (2)) for joint consideration by M2
	which is subsequently rejected by others within the group until the paragraph is created.

Table 7 .

 7 Episode

	from Session 3: Greek M ythology: Part 3
	F1 ((selects creation of new Paragraph))	P1
	F2 right what else	C
	M1 demi-gods	C
	F2 ((types demi-gods as Paragraph title))	C
	G ((all watch the interface as F2 types in the text))	C
	M1 shall we put demi-gods and demi-goddesses in the same thing	CL/P2
	F2 yes Courtiers wasn't it no that's in A M idsummer Night's Dream	CL/R2/A1
	(( confirms Paragraph Creation))
	F1 ((Selects Creates Paragraph))	F

Part 3 shows how, in the initiation of a third activity to create a paragraph with a title, there is joint attention to the activity shown through the number of individual and collective (verbal and non -verbal) Contributions, where M1s offering is taken up. As F2 types, M1s joint attention leads to a further Proposal

[START_REF] Bartu | Decisions and decision making in the Istanbul Exp loratory Pract ice experience[END_REF]

to expand the title. Negotiation involves F2, using both verbal and non-verbal means to reject this Proposal by completing her typing and confirming the paragraph creation, leading to finalisation.

Table 8 .

 8 Episode from Session 4: Sport vs Library


Ken Pfeuffer
email: k.pfeuffer@lancaster.ac.uk

Jason Alexander
email: j.alexander@lancaster.ac.uk

Hans Gellersen
email: h.gellersen@lancaster.ac.uk

Gaze+touch vs. Touch: What's the Trade-off when Using Gaze to Extend Touch to Remote Displays?

Keywords: Gaze Interaction, Eye-tracking, M ultitouch, M ultimodal UI

Direct touch input is employed on many devices, but it is inherently restricted to displays that are reachable by the user. Gaze input as a mediator can extend touch to remote displays -using gaze for remote selection, and touch for local manipulation -but at what cost and benefit? In this paper, we investigate the potential trade-off with four experiments that empirically compare remote Gaze+touch to standard touch. Our experiments investigate dragging, rotation, and scaling tasks. Results indicate that Gaze+touch is, compared to touch, 1) equally fast and more accurate for rotation and scaling, 2) slower and less accurate for dragging, and 3) enables selection of smaller targets. Our participants confirm this trend, and are positive about the relaxed finger placement of Gaze+touch. Our experiments provide detailed performance characteristics to consider for the design of Gaze+touch interaction of remote displays. We further discuss insights into strengths and drawbacks in contrast to direct touch.

Introduction

Multitouch gestures are now established on a variety of interactive surfaces such as phones, tablets, or tabletops, with much of their appeal based on the direct manipulation when touching the surface. It is of particular benefit to enable multitouch gestures on remote and large displays, as it is easy to learn, users are familiar with it, and users can easily manipulate content scattered across the large surface. However, the default touch is inherently restricted to interaction with direct surfaces in reach of the user. Although indirect interaction via a mediating mouse or touchpad can overcome this, the need for cursor dragging departs from the directness afforded by touch interaction.

A recent method to bring touch to remote displays is using the gaze modality as demonstrated in previous work ( [START_REF] Stellmach | Look & touch: gaze-supported target acquisition[END_REF][START_REF] Stellmach | Still looking: investigating seamless gaze-supported selection, positioning, and manipulation distant targets[END_REF][START_REF] Turner | Gaze+RST: integrating Gaze and multitouch for remote Rotate-Scale-Translate tasks[END_REF][START_REF] Turner | Eye Pull, Eye Push: M oving Objects between Large Screens and Personal Devices with Gaze & Touch[END_REF][START_REF] Turner | Cross-device Gaze-supported Point-to-point Content Transfer[END_REF]). The control of Gaze+touch is simple: users look at the target on the remote surface for selection, and perform touch gestures on the close-proximity surface. For example, as illustrated in Figure 1: the user looks at the target (a), touches down on the close surface (b), then performs a gesture with the same touches to manipulate the target (c). Gaze is used to determine the target at touch down, after which 'touch' takes over and manipulates the target. From an input-theoretic standpoint Gaze+touch is a technique that ties characteristics of both direct and indirect touch together. Similar to direct touch, users can initiate manipulation the moment they touch down without prior cursor dragging as needed in common indirect touch techniques. Similar to indirect touch, users leverage a relaxed finger placement, use varying control-display gains, and avoid fat-finger and occlusion issues commonly associated with direct touch. For this reason, Gaze+touch should be considered as a hybrid technique rather than an instance of either direct or indirect category, which argues for a gradual characterisation of Gaze+touch through explorative evaluation as initiated in prior work [START_REF] Pfeuffer | Gaze-touch: Combining Gaze with M ulti-touch for Interaction on the Same Surface[END_REF][START_REF] Stellmach | Look & touch: gaze-supported target acquisition[END_REF].

Yet, in light of real-world applicability, most present devices employ direct touch, making the similarities to direct touch particularly interesting. Considering a holistic perspective on 'multitouch', with regards to the entirety of direct manipulation rather than focusing on single gestures , Gaze+touch can be regarded as a method to bring all multitouch as it is to remote displays by using gaze as the mediator [START_REF] Stellmach | Look & touch: gaze-supported target acquisition[END_REF]. With this assumed, the question of trade-off becomes essential: what potential costs and benefits come with extending touch to remote displays ? How does gaze selection affect the ease and familiarity of multitouch, and the quality of multi-finger and multi-hand interaction? Prior work compared Gaze+touch to head-movement based techniques [START_REF] Stellmach | Look & touch: gaze-supported target acquisition[END_REF][START_REF] Stellmach | Still looking: investigating seamless gaze-supported selection, positioning, and manipulation distant targets[END_REF], to touch in a theoretical analysis [START_REF] Pfeuffer | Gaze-touch: Combining Gaze with M ulti-touch for Interaction on the Same Surface[END_REF], and between Gaze+touch variations for content transfer [START_REF] Turner | Eye Pull, Eye Push: M oving Objects between Large Screens and Personal Devices with Gaze & Touch[END_REF][START_REF] Turner | Cross-device Gaze-supported Point-to-point Content Transfer[END_REF] as well as large screens [START_REF] Turner | Gaze+RST: integrating Gaze and multitouch for remote Rotate-Scale-Translate tasks[END_REF]. However, we are not aware of any work that empirically contrasted Gaze+touch to the default touch paradigm.

In this paper, we contribute four experiments that each compare remote Gaze+touch to standard touch interaction. The overall research question is what costs and benefits come with making touch indirect by gaze. The experiments regard task completion time, accuracy, and user feedback using the techniques. As 'multitouch' includes a broad range of gestures, we focus on the fo llowing commonly used gestures. Each gesture corresponds to one experiment:

1. Single-touch dragging of objects. 2. Two-touch rotation of objects across different sizes. 3. Two-touch rotation of objects of different orientations. 4. Two-touch scaling of objects.

Our experiments resulted in the following findings:  Completion Time: Gaze+touch is as fast as touch for rotation and scaling, but slower for single-touch dragging.  Accuracy: Gaze+touch is more accurate for rotation and scaling, but less accurate for dragging.  Fat-Finger Problem: Gaze+touch allows to select smaller targets than touch.  User preference: Gaze+touch is preferred for rotation and scaling, and touch is preferred for dragging.

These findings depict strength (e.g. accuracy) and shortcomings (e.g. draggin g) that can be taken into consideration when designing Gaze+touch based user interfaces. While further validation is needed with real-world applicability and advanced technique design, our studies represent first groundwork in how Gaze+touch competes with and sets itself apart to standard touch interaction.

Related Work

The related work can be considered from two perspectives: research that evaluated gaze techniques, and research that evaluated touch techniques. Accordingly, we investigate the intersection of the domains by contrasting Gaze+touch to touch.

Evaluation of Gaze-based Interaction

Gaze interaction is considered as fast and natural, but suffers from the Midas Touch problem (false positive activation of tasks, [START_REF] Jacob | What you look at is what you get: eye movement-based interaction techniques[END_REF][START_REF] Jacob | Eye M ovement-Based Human-Computer Interaction Techniques: Toward Non-Command Interfaces[END_REF][START_REF] Stellmach | Still looking: investigating seamless gaze-supported selection, positioning, and manipulation distant targets[END_REF]). Early work therefore experimented using gaze pointing with dwell-time or button-press selection ( [START_REF] Jacob | What you look at is what you get: eye movement-based interaction techniques[END_REF][START_REF] Ware | An Evaluation of an Eye Tracker As a Device for Computer Input[END_REF]). Sibert and Jacob compared gaze with dwell-time against mouse; resulting in gaze being faster than the mouse [START_REF] Sibert | Evaluation of eye gaze interaction[END_REF]. MAGIC uses gaze to replace most of the pointing of a manual device [START_REF] Zhai | M anual and gaze input cascaded (M AGIC) pointing[END_REF]. They compared MAGIC to a trackpad and found MAGIC to be faster while reducing physical effort and fatigue.

Touch received increased attention in recent time as a partner for gaze pointing ( [START_REF] Stellmach | Look & touch: gaze-supported target acquisition[END_REF][START_REF] Stellmach | Still looking: investigating seamless gaze-supported selection, positioning, and manipulation distant targets[END_REF][START_REF] Turner | Gaze+RST: integrating Gaze and multitouch for remote Rotate-Scale-Translate tasks[END_REF][START_REF] Turner | Eye Pull, Eye Push: M oving Objects between Large Screens and Personal Devices with Gaze & Touch[END_REF][START_REF] Turner | Cross-device Gaze-supported Point-to-point Content Transfer[END_REF]). As touch is prime input for smartphones and tablets, it is particularly useful for interaction over distance where users point by gaze on remote displays , and confirm by touch on their local device. Stellmach and Dachselt first showed that Gaze+touch can improve selection accuracy that gaze-only usually lacks [START_REF] Stellmach | Look & touch: gaze-supported target acquisition[END_REF]. In a later work they showed that this combination also allows for dragging, scaling, and rotation of targets on distant displays [START_REF] Stellmach | Still looking: investigating seamless gaze-supported selection, positioning, and manipulation distant targets[END_REF]. In both works, Gaze+touch was compared to head based pointing techniques, and indicated performance benefit for using Gaze+touch. Turner et al. also investigated Gaze+touch with handheld and remote display, focusing on content transfer across devices ( [START_REF] Turner | Eye Pull, Eye Push: M oving Objects between Large Screens and Personal Devices with Gaze & Touch[END_REF][START_REF] Turner | Cross-device Gaze-supported Point-to-point Content Transfer[END_REF]). They studied transfer techniques based on gaze pointing with varying touch actions, showing general user acceptance and the importance of visual feedback and eye-hand coordination. Turner et al. also investigated gaze-supported rotate, scale, and translate (RST) gestures on large screens [START_REF] Turner | Gaze+RST: integrating Gaze and multitouch for remote Rotate-Scale-Translate tasks[END_REF], indicating how subtle differences in the design of Gaze+touch techniques affect remote RST interaction. Pfeuffer et al. investigated Gaze+touch for direct, in-reach surfaces [START_REF] Pfeuffer | Gaze-touch: Combining Gaze with M ulti-touch for Interaction on the Same Surface[END_REF]. In their design space analysis, they theoretically discussed Gaze+touch in contrast to touch, arguing that using gaze can avoid typical pitfalls of touch, such as occlusion or the fat-finger issue. Our work is complementary in providing an empirical comparison of remote Gaze+touch to standard touch.

Comparati ve Studies with Direct Touch

Kin et al. compared touch on a tabletop to an indirect setting of input by mouse and output on a desktop screen [START_REF] Kin | Determining the Benefits of Direct -touch, Bimanual, and M ultifinger Input on a M ultitouch Workstation[END_REF]. The user study showed that touch can improve performance in a multi-target task, when more than one finger is used for selection. Fo rlines et al. also compared touch to mouse on the same tabletop device [START_REF] Forlines | Direct-touch vs. M ouse Input for Tabletop Displays[END_REF], indicating that touch is more appropriate for multi-finger tasks and for multiple users but less for single cases.

Cursor-based indirect touch based techniques were developed based on offset [START_REF] Potter | Improving the Accuracy of Touch Screens: An Experimental Evaluation of Three Strategies[END_REF], multi-point [START_REF] Albinsson | High precision touch screen interaction[END_REF][START_REF] Benko | Design and Evaluation of Interaction M odels for M ulti-touch M ice[END_REF], and bimanual input [START_REF] Benko | Precise selection techniques for multi-touch screens[END_REF][START_REF] Wigdor | Rock & Rails: Extending M ultitouch Interactions with Shape Gestures to Enable Precise Spatial M anipulations[END_REF]. Potter et al. evaluated offset-based indirect touch to direct touch and found accuracy improved. Benko et al. compared indirect touch mice against direct touch [START_REF] Benko | Design and Evaluation of Interaction M odels for M ulti-touch M ice[END_REF]. They found that direct was faster as it allows explicit touch activation and resembles a single focus of interaction, contrasting the implicit cursor selection and dragging necessity . It is unclear whether these results apply to Gaze+touch since users can, like direct touch, manipulate the moment of touch down.

Other researchers proposed coupled drag gestures or consecutive touches to select small targets and increase mode selection [START_REF] Au | LinearDragger: A Linear Selector for Target Acquisition on Touch Screens[END_REF][START_REF] Gutwin | Faster Command Selection on Tablets with FastTap[END_REF]. However, these techniques occupy specific touch gestures and require learning of additional techniques.

Indirect touch techniques without cursor dragging were developed by mapping touchpad and remote display 1:1 ([12, 13, 18, 26]). Schmidt et al. compared this indirect touch variant (input on horizontal surface, output on vertical surface), to direct touch (input and output on horizontal surface, [START_REF] Schmidt | A Comparison Direct and Indirect M ulti-touch Input for Large Surfaces[END_REF]). Results showed lower performance with indirect touch, because users had difficulties to keep hands hovered over the surface while finding and selecting targets. With Gaze+touch, in contrast, users can touch down anywhere because selection is offloaded to gaze, eliminating the need to move and hover hands for long distances.

In summary, a variety of indirect touch techniques were developed in HCI literature and compared to direct touch as a baseline. Gaze+touch can be considered as a hybrid technique that inherits indirect characteristics without the drawbacks of cursor dragging nor absolute mappings. This makes it suited to transfer whole `multitouch' to remote displays. Collectively, these reasons motivated us to take a more detailed look on this transfer, and to conduct a comparative study of Gaze+touch to touch.

Method and Design of the Experiments

System. The system (Figure 2) consists of a touch display mounted at 30° close to the user (Acer T272), a large remote display (Samsung SUR40), and an eye tracker (Tobii X300). Both screens' resolution is 1080p. The close-proximity screen supports capacitive touch input for up to ten fingers, and the eye tracker uses 60 Hz gaze tracking. The close-proximity screen is used for input and output of touch, while Gaze+touch uses it only for touch input (with visual output on the remote screen). The software runs on the SUR40 PC (2x2.9 GHz CPU, 4 GB RAM), implemented in Java using the MT4J framework (https://code.google.com/p/mt4j/, 18/01/2015).

Eye Tracking Accuracy Mechanisms and Visual Feedback. We implemented three mechanisms to cope with issues of eye tracking hardware (e.g. imprecise tracking, eye jitter, and calibration offset, see [START_REF] Jacob | Eye M ovement-Based Human-Computer Interaction Techniques: Toward Non-Command Interfaces[END_REF][START_REF] Stellmach | Look & touch: gaze-supported target acquisition[END_REF]). First, we calibrate each time when users look at a target, but cannot select the target at all because of inaccuracy. We use Pursuit Calibration, a calibration method more flexible than standard procedures [START_REF] Pfeuffer | Pursuit Calibration: M aking Gaze Calibration Less Tedious and M ore Flexible[END_REF]. The calibration duration was 10 seconds, and on average users performed two to five calibrations during the study. Second, to cope with eye jitter, we average gaze samples for 150ms when only short eye movements occur (<2° of visual angle). Third, a gaze cursor appeared after the user fixated on a point for 1 second and did not select a target during that time. Not being able to select a target is noticeable, as usually the target is highlighted yellow when users looked it. The appearing cursor allowed the user to reposition the cursor by slight head movement if the system's gaze estimate was slightly offset preventing target selection (similar technique to Look and Lean [START_REF] Špakov | Look and Lean: Accurate Head-assisted Eye Pointing[END_REF]), yet allowed cursorless interaction for the majority of the time.

Fig. 2. Study setup.

Visual Angle as a Size Metric. To normalize measures of the close-proximity and the remote surface, we use degree of visual angle as a metric so that targets appear as the same size from the user's view. In the Touch condition, users were approximately 45cm in front of the screen's center. In the Gaze+touch condition, users were approximately 100cm from the screen (Figure 2). Thus absolute measures have a different size from the user's view. To normalize pixel measures, we use d egree of visual angle from the user's perspective as a metric for distance and size. For example, 1° of visual angle represents 25.1px on the direct condition, and 36.2px on the Gaze+touch condition. Figure 3 shows exemplary task designs for the Gaze+touch case: 3° (b), 2°x10° (d), or 4° (c and e).

Study Procedure. After completing a consent form, participants were given an introduction to the study, and then conducted the four exp eriments. They were instructed to perform each task as quickly and as accurately as possible, with speed taking priority. Before each experiment × technique block, the experimenter explained how the interaction technique is used, followed by a first trial with assistance. Each block was repeated five times. Notably, the whole first block was training (with assistance when necessary), and excluded from the final results. Each session lasted approximately 95 minutes. Task Procedure. Each task begins when the user touches the required number of fingers on the centre of the touchscreen, and (for Gaze+touch) looks at the centre of the remote screen. Based on a similar object dragging study [START_REF] Stellmach | Still looking: investigating seamless gaze-supported selection, positioning, and manipulation distant targets[END_REF], the object's starting position was always placed toward a random screen corner. For rotation and scaling tasks it was 10° from the screen's center; dragging tasks involved specific distances (described below). The user completed a task by pressing a button, although the actual finishing time is taken as the last time the user manipulated the object. After each experiment × technique block, the participant filled out a questionnaire. The cat egories were rated on a scale between 1 (strongly disagree) and 5 (strongly agree), and included 6 categories: ease of use, speed, accuracy, learning effort, eye tiredness, and physical effort. In addition, after each experiment users selected their preference of technique.

Experimental design. We used a within-subjects experimental design. Each user conducted the four experiments sequentially as presented in this paper. Within each experiment, the tested technique conditions were counterbalanced. All additional factors were randomized.

Participants. [START_REF] Potter | Improving the Accuracy of Touch Screens: An Experimental Evaluation of Three Strategies[END_REF]

Experiment 1: Object Dragging

We first investigate an object dragging task. Dragging is commonly used on touchscreens, such as for moving files into a folder, or when positioning icons. In our experimental task, users move objects from a start to a destination location.

Compared Interaction Techniques

 Touch: Select the object with direct touch, and drag the object to the destination. The object starting and destination position are on the close, direct display.  Gaze+touch 1:1 : Look at the object, touch down anywhere, indirectly drag object to the destination (Figure 4). The task is performed on the remote screen, while touches are issued on the close display. The finger movement translates 1:1 to object movement on remote screen).  Gaze+touch dynamic : Same procedure (Figure 4), but the movement translates relatively using a dynamic control-display (CD) gain. This amplifies dragging i.e. it is more precise at slow and faster at fast finger movement (based on Windows XP/Vista pointer ballistics, similar to [START_REF] Casiez | The Impact Control-Display Gain on User Performance in Pointing Tasks[END_REF]).

Experimental Design

The object's size is set to 3° which is 31 mm on close (31 mmc ) and 49 mm on remote display (49 mmr ). It appears towards a corner of the screen, and the dragging d irection is always toward the opposite diagonal corner. The target of the dragging was displayed as a grey circle (see Figure 3b). The independent variables were:  Dragging distance: 17.5° (185 mmc , 292 mmr ), and 35° (1210 mmc , 1307 mmr ) (between start and destination).  Destination size: 110% (34 mmc , 54 mmr ), 220% (69 mmc , 109 mmr ), and 330% (103 mmc , 164 mmr ) of the object size.

Overall, each user performs 90 trials: 3 techniques × 2 distances × 3 target sizes × 5 repetitions. All tasks were successfully completed by all users.

Results

 Task Completion Time: Task completion times are presented in Table 1, line 1-3.

A main effect of technique (F(2,30)=47.9, p<.001) showed that Touch is significantly faster than both Gaze+touch techniques (p<.001), and Gaze+touch dynamic was faster than Gaze+touch User Feedback: Participants' preferences were split during the dragging task, with 9 of the 16 users preferring Touch. The users' rationale for Touch was less mental demand (''my attention is not completely absorbed [with Touch]''), familiarity with this technique (''I have been using touchphones for a while, so it is a familiar technique''), ease, and speed of Touch (''it was easy and quick to perform the task'').

Arguments in favour of Gaze+touch were no occlusion (''Touch had the problem that you obscured the object''), the speed of the eyes (''the eyes were fas ter than the fingers on the screen''), and less perceived effort (''[with Touch] it felt there was more effort because you saw the hand moving''). Gaze+touch dynamic was preferred over Gaze+touch 1:1 by 13 of the 16 participants due to less physical movement with the hands.

Table 1. Quantitative results of the experiments ('green' denotes higher performance, `light green' denotes higher performance than 'white', asterisks denote significance, 'time' measured in seconds, 'accuracy' measured in visual angle).

 Questionnaire: The questionnaire's result is presented in Table 2, line 1-6. Statistical tests showed that for the category of perceived ease (Χ²(2,16)=12.1, p=.002), Touch was perceived easier than the Gaze+touch 2. Qualitative results of the experiments (1 = strongly disagree, 5 = strongly agree, 'green' denotes better rating, asterisks denote significance).

For eye tiredness (Χ²(2,16)=14.4, p=.001), users find Touch less tiring than Gaze+touch dynamic (Z=-2.57, p<0.05) and Gaze+touch 1:1 (Z=-2.86, p<0.05).

Discussion

Users were faster and more accurate with Touch, and Gaze+touch dynamic was faster than Gaze+touch 1:1 . User preferences did not show clear results, however they indicate that more users prefer using Touch. Further analysis of the questionnaire showed that users perceive Touch to be beneficial across most categories (ease, speed, accuracy, etc.). Regarding both Gaze+touch techniques in comparison, users preferred Gaze+touch dynamic over Gaze+touch 1:1 , for requiring less hand movement. The previous study investigated a single-touch context; we now study multitouch interaction beginning with rotation of objects. We also investigate the fat -finger problem: we hypothesise that Touch is affected, but not Gaze+touch as fingers can be placed more freely. The task is a two-finger rotation tasks. Participants had to select an object, and then rotate it to a specific orientation. In each task, the object's size and rotation angle is varied.

Compared Interaction Techniques

 Touch: The user directly puts two fingers on an object, then rotates it to a target orientation. Again, touches and manipulation occur on the close and direct display.

After users selected a target, users can also expand their fingers to manipulate the target more freely (as in all the following rotation and scaling experiments).  Gaze+touch: The user looks at the target, indirectly touches down two fingers, then rotates these fingers to rotate the s elected object (Figure 5).

Experimental Design

The target orientation was displayed underneath the object to visually indicate the rotation direction and angle (grey box, Figure 3c). The object and the target both displayed a line, which the users had to match to finish the rotation. The independent variables were:  Object size (visual angle): 1° (10 mmc , 16 mmr ), 2° (20 mmc , 33 mmr ), 4° (41 mmc , 66 mmr ), and 8° (83 mmc , 123 mmr ).  Rotation angle: 10°, 50°, and 90°.

The smallest size of 1° is chosen as a realistic lower limit of the used eye tracker. If users struggled with the acquisition of this target with Touch (as 1°=25px), they could skip the task. Overall, each user performs 120 trials: 2 techniques × 4 sizes × 3 rotation angles × 5 repetitions.

Results

 Error: All tasks were successfully completed with Gaze+touch, and users skipped 19% of tasks with Touch. In particular, 76% of tasks with a size of 1° were skipped, demonstrating the effect of the fat-finger problem. The error is illustrated in Figure 6. For the following statistical analysis, we excluded all trials with 1° to ensure an equal numbers of conditions. Fig. 6. Users skipped more tasks with Touch, as the fat-finger issue became apparent with small targets.

 Task Completion Time: ), yet 50° and 90° did not show significant differences. An interaction between technique and size (F(1.5,21.9)=35.68, p<.001), revealed that participants performed faster with Gaze+touch at the 2° tasks than with Touch (p<.001).  Accuracy: Accuracy is measured in degrees as the difference between the final angle of the object and that of the destination. The results are presented in Table 1, line 12-15. A main effect of technique (F(1,15)=20.32, p<.001) showed that Gaze+touch was significantly more accurate than Touch (p<.001). Accuracy increased with increasing object size (F(2,30)=129.59, p<.001, all pairs differ at p<.001), but not significantly with rotation angle. An interaction between tec hnique and size (F(2,30)=12.47, p<.001) showed that for target size 2° Gaze+touch was significantly more accurate than Touch (p<.01).  User Feedback: 15 of 16 users preferred Gaze+touch. Most users' reasons were based around the fat-finger problem (''I wasn't constrained by finger size'').  Questionnaire: The questionnaire's result is s hown in Table 2, line 7-12. The following statistical differences were revealed. For category ease (Χ²(1,16)=12, p=.001), Gaze+touch was perceived as easier than Touch. For category speed (Χ²(1,16)=13, p=.0), Gaze+touch was perceived as faster than Touch. For category accuracy (Χ²(1,16)=16, p=.0), Gaze+touch was perceived as more accurate than Touch. For category eye tiredness (Χ²(1,16)=7.4, p=.007), Gaze+touch was perceived as more eye tiring than Touch.

Discussion

Users skipped more tasks when selecting small targets with Touch, a result that was expected considering the fat-finger issue. Gaze+touch did not show any errors across all target sizes, indicating that a gaze-selection is more accurate than a raw Touch-selection for two-touch gestures. Users were faster with Gaze+touch for small targets as they were easier to acquire (size ≤ 2°). In case of accuracy, users performed more accurate than Touch in the rotation tasks with small targets, which can be accounted to the more relaxed placement of fingers. User feedback confirms these results, most users preferred Gaze+touch for being less constrained to finger size.

Experiment 3: Object Rotation (Varying Object Orientation)

The previous study investigated rotation of objects with varying object sizes. A nother important factor for rotation is the initial orientation of targets which can affect the user's performance [START_REF] Hoggan | M ulti-touch Rotation Gestures: Performance and Ergonomics[END_REF]. We therefore investigate this context in our third experiment, where users perform unimanual rotation gestures. In each task, the object's initial orientation and the rotation direction are varied.

Compared Interaction Techniques

 Touch: The user directly puts two fingers of the same hand on an object, then rotates it to a target rotation.

 Gaze+touch: The user looks at the target, indirectly touches down two fingers of the same hand, then rotates these fingers to rotate the selected object (Figure 7).

Experimental Design

The target object is a rectangle with a width of 2° (20 mmc , 33 mmr ) and a height of 10° (104 mmc , 166 mmr ), and the angle of required rotation is fixed at 90°. We chose 2° as it allowed users to comfortably place their fingers on the object. The target orientation was indicated underneath the object with a rectangle and with an arrow to visually indicate the rotation direction and angle (Figure 3). Independent variables were:

 Object starting orientation: 0°, 45°, 90°, and 135° relative to the screen's x-axis.  Rotation direction: clockwise or anticlockwise.

Overall, users perform 90 trials: 2 techniques × 4 initial orientations × 2 directions × 5 repetitions. The participants completed all tasks with both techniques.

Results

 Task Completion Time: No significant effects were found for task completion times; users performed similarly fast with both techniques (Table 1, line 16).  Accuracy: A significant main effect of technique for accuracy (again measured in angle difference, F(1,15)=19.43, p<.01) revealed that Gaze+touch was more accurate than Touch (Table 1, line 17).  User Feedback: 12 of 16 users preferred rotation with Gaze+touch, with the reason that Touch, with differently oriented objects, made some objects hard to acquire (''You do not need to put the hand on the object'').

 Questionnaire: Results are shown in Table 2, line 13-18. In category ease of use, users perceived Gaze+touch as easier than Touch (Χ²(1,16)=5.4, p=.02). For category eye tiredness (Χ²(1,16)=6.4, p=.011), Gaze+touch was perceived as more eye tiring than Touch. For category physical effort (Χ²(1,16)=6.4, p=.011), Gaze+touch was perceived as less physically demanding than Touch.

Discussion

Overall, users performed equally fast with both techniques, but more accurately with Gaze+touch. Contrasting the first rotation study (Experiment 2), no difference in speed is found because the target size remained fixed for all tasks in this experiment. However, users were more accurate with Gaze+touch, again to be accounted to the relaxed finger placement, as users indicated objects are difficult to acquire with Touch. The questionnaire showed that users perceived Gaze+touch as easier and as less physically demanding, although more eye tiring.

Experiment 4: Object Scaling

Our previous experiments investigated dragging and rotation tasks. Another prev alent gesture for multitouch is pinch-to-scale, often used to scale images, maps, or other objects. This experiment assesses users' performance of Gaze+touch in a scaling task. Object size and scaling amplitude is varied. We let users choose between uni-or bi-manual interaction.

Compared Interaction Techniques

 Touch: The user directly puts two fingers on an object, then pinches them to fit an outline of a differently scaled target.  Gaze+touch 1:1 : The user looks at the target, indirectly touches down two fingers, then pinches them to scale (Figure 8). The scaling translates absolutely, thus finger movement is 1:1 applied to the object's scaling.  Gaze+touch dynamic : Same operation (Figure 8). However, the scaling translates with a different control-display gain, the distance between both fingers is relative to the width of the object.

Experimental Design

Users had to scale an object to a specific size which was visually indicated by a black rectangle (see Figure 3). The independent variables were:  Initial object size (visual angle): 1° (10 mmc , 16 mmr ), 2° (20 mmc , 33 mmr ), 4° (41 mmc , 66 mmr ), and 8° (83 mmc , 123 mmr ).  Scaling factor: 50%, 90%, 120%, and 200% of the initial object's size.

Overall, a user did 240 trials: 3 techniques × 4 sizes × 4 scale factors × 5 repetitions.

Results

 Error: Participants completed all tasks with Gaze+touch, and skipped 24.7% tasks with Touch (c.f. Fig. 6). In particular, users skipped with Touch within 1° tasks 100% of both downscaling conditions, 68

Discussion

Similar to experiment rotation (size), users had difficulties acquiring small targets with Touch (fat-finger issue). Despite small targets, users performed similarly fast with Gaze+touch and Touch, while more accurate with Gaze+touch. Only for large targets, Touch was faster than Gaze+touch. Users' reasons were about the fat-finger problem (occlusion, fatigue). Considering both Gaze+touch variants, users can scale smaller objects faster with Gaze+touch 1:1 . User opinion was split, half of them preferred Gaze+touch 1:1 and the remaining users preferred Gaze+touch dynamic .

Overall Discussion

Our experiments investigated how Gaze+touch combines properties of direct (same gesture operation) and indirect touch (relaxed finger placement), which we follow up with a high level discussion on the following points: Advantages of Gaze+touch. The relaxed finger placement can reduce effects of the fat-finger and occlusion issues. This was particularly beneficial for rotation and scaling tasks, where more than one finger is used for manipulation. Our experiments showed that with the design techniques, users performed similarly fast, and more accurately than with Touch. Manipulation of objects with a size of <2° was not feas ible with Touch, however with Gaze+touch, users were able to manipulate the 1° o bjects (although completion time increased).

Shortfalls of Gaze+touch.

Gaze+touch was slower and less accurate for dragging tasks. Based on observations and feedback, we believe this is accounted to two aspects. First, the `leave-before-click' issue [START_REF] Salvucci | Intelligent Gaze-added Interfaces[END_REF]: users can already look away from a target before they touch down, or touch down before they look at the target; both will void a Gaze+touch selection. Second, users could `lose' a target during dragging, e.g. when the system wrongly detected a `touch up' event or the user's finger briefly hovered. With direct touch, the finger is on the target, thus the system will immediately receive a `touch down' event and the dragging continues. However, with Gaze+touch, it is indirect touch, and to reselect users have to look to the target before they touch down. Both advantages and shortfalls correlated with the users' feedback.

Control-Display Gain. The relaxed finger placement allowed us to experiment with dynamic CD gains (Gaze+touch dynamic ). During dragging, this led to faster performance than a 1:1 mapping of Gaze+touch. It eliminated the need to clutch when the touch screen's size did not suffice, confirming previous studies of cursor acceleration [START_REF] Casiez | The Impact Control-Display Gain on User Performance in Pointing Tasks[END_REF]. CD gain in scaling tasks did not use acceleration, but rather input relative to the fingers' distance. Users were faster with the absolute scaling, but more precise with relative scaling.

Observations. We observed users exploiting the relaxed finger placement as a strategy to improve their performance: for long rotations, users had their fingers drawn together to manipulate faster, while for short rotations, users set them further apart to be more accurate. Although technically normal touch allows the same operation, it is restricted by a lower limit, as for small targets users have little room to adjust their fingers on it, and an upper limit, defined by the object's size (although users can expand their fingers once they selected an object).

Limitations. Users were slower with Gaze+touch for dragging tasks. One method to overcome this could be using gaze for target dragging: after a touch selection, the target follows the user's gaze ( [START_REF] Stellmach | Still looking: investigating seamless gaze-supported selection, positioning, and manipulation distant targets[END_REF][START_REF] Turner | Eye Pull, Eye Push: M oving Objects between Large Screens and Personal Devices with Gaze & Touch[END_REF][START_REF] Turner | Cross-device Gaze-supported Point-to-point Content Transfer[END_REF]). Future studies can investigate how this advanced technique would compare to standard touch dragging. In addition, our experiments compared Gaze+touch against the raw default of direct touch. This is apparently prone to issues such as the fat-finger problem or occlusion. These issues can be overcome, e.g. by indirect touch techniques ( [START_REF] Albinsson | High precision touch screen interaction[END_REF][START_REF] Benko | Precise selection techniques for multi-touch screens[END_REF]), and should be considered in future evaluation.

Conclusion

Gaze as a mediator can bring touch to remote displays, but at what cost and benefit? As a first step, we compared Gaze+touch to touch in four experiments across dragging, rotation, and scaling tasks. Our experiments provide detailed performance characteristics of both input modes, and indicate that while Gaze+touch is slower and less accurate for dragging tasks, users are equally fast and more accurate in rotation and scaling tasks. This can support the design of Gaze+touch interaction for remote displays, such as combined close and remote surfaces consistently controlled by multitouch. In light that further evaluation beyond abstract tasks may be required to validate the real-world applicability, our experiments provide empirical groundwork in the exploration of how Gaze+touch sets itself apart from touch interaction.

Fig. 1 .

 1 Fig. 1. Gaze can be used to bring multitouch to remote surfaces: (a) look at the target, (b) touch down, and (c) perform a multitouch gesture with the same touches.

Fig. 3 .

 3 Fig. 3. Example user setup (a) and design of each experiment: dragging (b), rotation across sizes (c), rotation across orientations (d), and scaling (e). Lines show the mapping between finger and object (not visible during study).

Fig. 4 .

 4 Drag with Gaze+touch: look at the object (a), touch down (b), and drag (c).

Fig. 5 .

 5 Fig. 5. Gaze+ touch: look at the object (a), touch down two fingers (b), and rotate (c).

Fig. 7 .

 7 Fig. 7. Rotate with Gaze+touch: look (a), touch down two fingers of one hand (b), and rotate (c).

Fig. 8 .

 8 Fig. 8. Gaze+touch scaling: look (a), touch down two fingers (b), and pinch (c).

  Accuracy is the distance between the object's final position and center of the destination, normalized to degree of visual angle to allow direct comparison .

1:1 (p<.05). Participants were slower with increasing distance (F(1,15)=86.26, p<.001). An interaction effect between technique and distance (F(1.3,19.3)=9.58, p<.01) showed Touch was the fastest technique across both distances (p<.01). Further, Gaze+touch dynamic was faster than Gaze+touch 1:1 on 35° distance (p<.001), which can be accounted to CD gain.  Accuracy: Results are listed in Table

1

, line 4-6. A main effect of technique (F(1.9,28.8) =5.17, p<.05) showed that users were overall more accurate with Touch than both Gaze+touch techniques (p<.05). Further, users were more accurate with shorter distances (F(1,15)=23.63, p<.001) and larger target sizes (F(2,30)=23.91, p<.001, all pairs differ, p<.01).

  Table 1 line 8-11 summarise task completion times. A main effect of technique (F(1,15)=6.12, p<.05) showed that overall users were significantly faster with the Gaze+touch technique (p<.05). A main effect of object size (F(1.3,19.3)=40.77, p<.001) showed that object size affected task completion time: tasks with 2° sized objects were significantly slower than 4° and 8° (p<.001),

yet no difference was found between 4° and 8°. Similarly with rotation angle (F(2,30)=17.23, p<.001), task completion time decreased at 10° (p<.01

  .8% upscaling-to-120% tasks, and 56.3% upscaling-to-200% tasks; and within 2° tasks 29.7% downscaling-to-50% tasks, and 40.6% downscaling-to-90% tasks. Like in Experiment 2, we exclude skippedtask conditions from statistics for an equal number of trials between techniques.  Task Completion Time: Task completion times results are summarised in Table 1, line 19-22. There was no significant difference for technique at task completion time. A significant main effect for object size (F(2,30)=7.68, p<.01) showed that users performed faster with 4° than 8° objects (p<.01). A main effect of target size (F(1,15)=34.98, p<.01) revealed that users were faster with 120% than 200% u pscaling (p<.05). An interaction between technique and the object's size (F(2.3,33.8)=7.6, p<.01) showed that within 2° sized object tasks, users performed faster with Gaze+touch 1:1 than with Gaze+touch dynamic (p<.05), and within 8° tasks, users were faster with Touch than with either Gaze+touch technique (p<.05). Results are presented in Table 2, line 19-24.

	 Accuracy: Accuracy (the difference between radius of the object and radius of the
	target, normalized to degree of visual angle) showed a main effect of technique
	(F(2,30)=9.8, p<.01) with users more accurate with both Gaze+touch techniques
	than with Touch (p<.05, Table 1, line 23-27).
	For category ease
	(Χ²(2,16)=26, p=.0001), Gaze+touch dynamic (Z=-3.4, p<0.05) and Gaze+touch 1:1
	(Z=-3.5, p<0.05) were perceived as easier than Touch. For category speed
	(Χ²(2,16)=19.4, p=.0001), Gaze+touch dynamic (Z=-2.9, p<0.05) and Gaze+touch 1:1
	(Z=-3.3, p<0.05) were perceived as faster than Touch. For category accuracy
	(Χ²(2,16)=24.6, p=.0001), Gaze+touch dynamic (Z=-3.4, p<0.05) and Gaze+touch 1:1
	(Z=-3.3, p<0.05) were perceived as more accurate than Touch. For category eye
	tiredness (Χ²(2,16)=16.8, p=.0001), Gaze+touch dynamic (Z=-3, p<0.05) and
	Gaze+touch 1:1 (Z=-3.1, p<0.05) were perceived as more tiring than Touch.

 User Feedback: All users preferred using one of the Gaze+touch techniques. The user's reason were based around the fat-finger problem (''I could not get both fingers within the box''), occlusion, and hand fatigue (''my arms do not get so tired because I can rest on the desk''). Between both Gaze+touch techniques, 8 users preferred Gaze+touch dynamic , and the other 8 users Gaze+touch 1:1 . Reasons were more precision with Gaze+touch dynamic (''I was more precise''), and speed for Gaze+touch 1:1 (''[Gaze+touch dynamic ] is slower [than Gaze+touch 1:1 ], because your fingers need to make a bigger movement'').  Questionnaire: