Kazuki Takashima
email: takashima@riec.tohoku.ac.jp

Yusuke Asari

Hitomi Yokoyama
email: hitomi-y@cc.tuat.ac.jp

Ehud Sharlin

Yoshifumi Kitamura
email: kitamura@riec.tohoku.ac.jp

MovemenTable: The Design of Moving Interactive Tabletops

Keywords: Human-robot interaction, social interfaces, and CSCW

à la diffusion 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

Interactive surfaces such as tabletops and large interactive displays provide a collaborative focal point, allowing people to gather around them and to engage in various tasks, individually or as a group. By dynamically changing their locations around interactive surfaces people can engage in tasks, change their role in a collaborative setting, protect their privacy, and disengage from a task by simply stepping away from the surface [START_REF] Marquardt | Proxemic interactions: from theory to practice[END_REF][START_REF] Ryall | Exploring the effects of group size and table size on interactions with tabletop shared-display groupware[END_REF]. These benefits of interactive surfaces are founded on the ways people use furniture and tables for thousands of years, augmenting the classic table with the additional advantages of computation and interactive visualization [START_REF] Ryall | Exploring the effects of group size and table size on interactions with tabletop shared-display groupware[END_REF][START_REF] Tang | Collaborative coupling over tabletop displays[END_REF]. More than a decade ago ConnecTables presented interactive displays that can be merged, manually, in order to affect the workspace and the interaction around it [START_REF] Tandler | ConnecTables: dynamic coupling of displays for flexible creation of shared workspaces[END_REF]. The premise is that changing the physicality of the interactive spaces we provide users will impact their interactive experience and affect the quality of their collaboration. We pursue this vision by proposing interactive surfaces that can automatically deform, move, connect and disconnect, changing their size, location and shape according to users' need. Recently, TransformTable explored interactive surfaces that can deform in order to address different tasks and collaborative needs [START_REF] Takashima | TransfomTable: a self-actuated shape-changing digital table[END_REF]. In this paper we propose interactive surfaces that can automatically change their positions in order to address different tasks and collaborative settings, and present a design exploration of this vision.

Our exploration is based on a set of practical prototypes we call MovemenTables (Fig. 1). MovemenTables (MT) can move, rearrange, connect and disconnect in various forms according to task and needs. MT's movements can follow users' requests, or be mediated by collaborative or social need, and autonomously initiated. Realizing MT required us to tackle three main challenges.

(1) Technical implementation of MovemenTable. We implemented two MT prototypes, MovemenTable Senior and MovemenTable Junior, following a humanrobot Interaction (HRI) design approach. In the technical sense MT can be viewed as a robotic interactive tabletop that autonomously moves, can be tracked and benefits from some level of situational awareness of its environment [START_REF] Drury | Awareness in human-robot interactions[END_REF].

(2) Designing motion cues with tabletop content. In order to be more socially acceptable to the people interacting with it, MTs should provide simple cues regarding their movements, clearly expressing their intent to start moving, to turn, or to stop. Previous research shows that people can infer goal and intent from non-verbal motion cues [START_REF] Blythe | How motion reveals intentions: categorizing social interactions[END_REF][START_REF] Heider | An experimental study of apparent behavior[END_REF][START_REF] Kwon | The squash-and-stretch stylization for character motions[END_REF]. This tendency to relate social intent to even abstract motion cues was later explored in HCI and HRI (e.g., [START_REF] Mutlu | The use of abstraction and motion in the design of social interfaces[END_REF][START_REF] Takayama | Expressing thought: improving robot readability with animation principles[END_REF]). MTs are employing a similar approach, communicating their physical locomotion intentions using motion stylization of the interactive visual content the display. In essence, MT is using its tabletop visual content as if it is an animated cartoon character, styling, squashing, stretching and augmenting the visual content in order to communicate its locomotion intent.

(3) MT's user experience. Ultimately, MT's goal is to impact users' interactive social experiences. Provided with sufficient social awareness, MTs can attempt to support, and even guide people's social interactions by moving, connecting or disconnecting. For example, two or more MTs may connect in order to provide a wide interactive display for a large group of users, or break away when users are engaged in different tasks or require privacy. MT can take advantage of their spatial relationships and proxemics [START_REF] Hall | The hidden dimension[END_REF][START_REF] Marquardt | Proxemic interactions: from theory to practice[END_REF] to people in order to socially guide the interaction, for example by approaching a reluctant user, or provide privacy to one group of people by avoiding others. While our work stop short of tackling these challenges in practice and in naturalistic setting, we report the results of an extensive experimental study of the fundamental attributes of MT, confirming that MT's motion stylization cues help users infer its movement intention (study 1), that MT's basic spatial movements are recognizable and socially acceptable by users (study 2), and that the basic movements of a single or of multiple MTs impact users' spatial behaviors and perspective around the MTs in interactive and collaborative settings (study 3 and 4). This paper reports how we pursued the aforementioned three MT research threads, the insight gained on the concept of automatically moving tabletop interfaces, and the remaining challenges.

2

Related Work

Social Interactions and Tabletops

The physicality of tabletop interfaces was shown to affect the social interaction between users, for example by influencing people's personal spaces and their spatial arrangements around the surface (e.g., territoriality [START_REF] Scott | Territoriality in collaborative tabletop workspaces[END_REF], group coupling [START_REF] Tang | Collaborative coupling over tabletop displays[END_REF]). The design of better collaborative tabletop workspaces was shown to be affected by the table and group size [START_REF] Ryall | Exploring the effects of group size and table size on interactions with tabletop shared-display groupware[END_REF]. While these effects were observed and reflected upon, static tabletop interfaces are not capable of dynamically changing their physicality and cannot physically affect the spatial behaviors of people interacting with them.

In collaborations, workspace dynamic connections have been well researched with personal tabletop [START_REF] Tandler | ConnecTables: dynamic coupling of displays for flexible creation of shared workspaces[END_REF] and personal tablets [START_REF] Marquardt | Cross-device interaction via micromobility and f-formations[END_REF]. ConnecTable [START_REF] Tandler | ConnecTables: dynamic coupling of displays for flexible creation of shared workspaces[END_REF] is a manually movable personal tabletop display, motivated by the simple social observation that people move closer to each other when engaged in discussions. Two ConnecTable displays can be seamlessly coupled in order to create a larger display workspace, or can be detached to provide two separate interaction spaces. TransformTable is a selfactuated shape-changing tabletop display enabling basic deformations of its interactive surface according to task and interaction settings, but with no locomotion capabilities [START_REF] Takashima | TransfomTable: a self-actuated shape-changing digital table[END_REF]. MT is extending these past efforts by integrating locomotion capabilities in interactive tabletops, and examining how their intentional movement affects people's spatial behaviors and experience during collaborative interaction. MT's dynamic spatial relationships with users closely relates to research on spatial relationships between displays, interfaces and people, for example proxemics interactions [START_REF] Marquardt | Proxemic interactions: from theory to practice[END_REF] and F-Formation [START_REF] Marquardt | Cross-device interaction via micromobility and f-formations[END_REF]. The concept of space-aware interactive tabletops which detect and sense their users was explored in static tabletop interfaces (e.g, [START_REF] Annett | Medusa: a proximity-aware multi-touch tabletop[END_REF]).

Human-Robot Interaction and Robotic Tables

MT is practically a robotic tabletop interface. Interaction between people and robots was shown to follow behavioral and social spatial interpersonal principles, such as proxemics [START_REF] Satake | How to approach humans? -strategies for social robots to initiate interaction[END_REF] and the design of MT and its movements is informed by these themes.

MT augmentation of its physical movements using classic cartoon art and motion stylization techniques [START_REF] Kwon | The squash-and-stretch stylization for character motions[END_REF][START_REF] Masuch | Speedlines -depicting motion in motionless pictures[END_REF], allows it to express its locomotion intentions. Animation and cartoon art techniques were previously introduced to HRI (e.g., [START_REF] Takayama | Expressing thought: improving robot readability with animation principles[END_REF][START_REF] Young | Robot expressionism through cartooning[END_REF]), though MT's adaptation of these principles to interactive tabletops is, as far as we know, new in its transformation of the tabletop visual content into an implicit animated character providing motion cues to the user. Past research in robotic interfaces proposed the concept of robotic tables. For example, [START_REF] Sawada | Autonomous re-alignment of multiple table robots[END_REF] implemented multiple table robots that could autonomously change their positions and arrangement according to different tasks. The project was focusing on actuating the classic table furniture, and did not address interactive tabletops, motion cues, or the collaborative tasks that tabletop interfaces afford.

MovemenTable

We designed two types of MovemenTable prototypes: MovemenTable Senior (MTSr.) and MovemenTable Junior (MTJr). MTSr is more robust, providing a larger interactive space for small group collaboration and implemented using an internal rear-projector, while the smaller MTJr is designed for personal use, and is implemented using a commercial touch display and a Roomba for its locomotion.

The MT prototypes are being controlled by an off-board server that communicates with the MTs and handles their movements. The server synchronizes the MTs coordinated actions, for example connection or separation of two MTs. The server also helps easy administration of the MT Wizard of Oz (WoZ [START_REF] Riek | Wizard of Oz Studies in HRI: a systematic review and new reporting guidelines[END_REF]) algorithms we employed when evaluating the tabletops.

MovemenTable Senior

MTSr is a wheeled robotic interactive tabletop display (Fig. 2a), 96x96x100cm (WxDxH) in size. The physical dimensions of MTSr were chosen to allow four adults to comfortably interact with the tabletop. The interactive surface is a typical FTIR tabletop with rear projection, using a 40', 850x850mm screen, with maximum projection area of about 800x600mm, and 4:3 aspect ratio. The projector is fed by an external PC using a wireless HDMI connection. MTSr requires an external power supply to drive the projector and is carrying a power extension cord as it moves about. MTSr's locomotion is controlled by an onboard PIC microcontroller, which communicates with an external PC through Bluetooth and manages the motor driver. MTSr translates and rotates using a traditional differential two wheeled robot at the bottom of the table enclosure. MTSr controls its translation, with speeds of around 0.3 m/sec, and rotation, with speeds of around π/4 rad/sec. The location and the orientation of MTSr and its users are being tracked using a motion capture system.

MovemenTable Junior

MTJr is a smaller robotic table that is designed for personal use. It carries a commercial touch display (27 inch full HD, 1980 x 1080 pixels display, IIyama ProLiteT27), controlled by a laptop and buttery within the MTJr enclosure. MTJr is completely wireless and carries its own standalone battery power supply. For locomotion, MTJr uses a Roomba with Bluetooth receiver (RombaSCI), mounted below the MTJr wheeled alumni frame box enclosure (67x42x90cm WxDxH, in dimension, see Fig. 2b) enabling movement capabilities which are identical to MTSr. MTJr's maximum speeds are 0.5 m/sec in translation and π/3 rad/sec in rotation. In our fourth study (described in Section 6.2, below) we explored fundamental MT's connecting and separating movements using two MTJrs.

Visual Motion Cues

To provide users with motion cues about the MTs movements and spatial intentions we implemented an augmentation of the MT's physical movements with visual motion cues (Fig. 3). While other motion cue modalities can be implemented, the current prototype of MT was designed so it will be as true as possible to its tabletop metaphor, rather than becoming, for example, a speaking or arms waving robot. MT is using its current visual tabletop content to create a set of implicit animated characters that convey its locomotion intentions via non-verbal motion cues. In principle MT's motion cues can incorporate a rich variety of motion stylization and animated cartoon art techniques, for example, MT could use different motion cues to express different emotive motions such as hesitation, determination, shyness, or submission [START_REF] Young | Teaching robots style: designing and evaluating style-by-demonstration for interactive robotic locomotion[END_REF]. Our current MT prototype provides motion cues only for basic straight movement, using five movement phases: ready, set, go, stop and relax. When the MT is about to move it generates motion cues for the five movement phases by capturing its current visual tabletop content and using it as an implicit animated character. The visual content will then be used to generate the different animated motion stylizations, which are informed by animation techniques such speedlines [START_REF] Masuch | Speedlines -depicting motion in motionless pictures[END_REF] and squash-and-stretch [START_REF] Kwon | The squash-and-stretch stylization for character motions[END_REF]. Below we briefly discuss the implementation of the five movement phases based on the cartoon squash-and-stretch [START_REF] Kwon | The squash-and-stretch stylization for character motions[END_REF] steps (Fig. 4). Ready MT disables the touch input on its interactive surface and freezes the screen content. The screen content is captured as an image and mapped onto a 20x15 points grid (Fig. 3a). Following that, the image, using the point grid, dynamically deforms, contracting onto itself and shrinking slightly over two seconds in a sequence that suggests concentration and preparation for oncoming events. A side effect of the ready shrinking is that it frees screen space which subsequent movement phases use for their motion stylizations (e.g. drawing speed-lines).

Set This motion cue was designed to generate anticipation to movement towards a specific direction. The squash cue [START_REF] Kwon | The squash-and-stretch stylization for character motions[END_REF] and the level of exaggeration, provide indication of the intended movement direction, as well as a sense of the expected distance (Fig. 3b). The duration of the compression animation is 500 msec, and the compressed form is kept for another 200 msec before moving to the next motion cue.

Go This phase initiates and augments MT's actual physical movement towards its intended direction, as shown at the Set phase. As MT starts to move the tabletop image is quickly stretched and deformed into an arrow-like shape, pointing towards the physical movement direction (Fig. 3c). Go also includes dynamically moving speedlines and shadows [START_REF] Masuch | Speedlines -depicting motion in motionless pictures[END_REF] which are overlaid behind the arrowed image to further augment MT's physical movement, stopping only when MT reached its destination. During Relax the touch input on the screen is re-enabled. The Relax cue is designed to clearly show that MT's physical movements are all done, prompting users to reengage with the tabletop interactive content (Fig. 3e)

Stop

Interaction Scenarios with MovemenTables

In this section we assume that MTs is provided with sufficient social and situational awareness of the users surrounding it, e.g., their position, orientation, group size, and some low-level of insight on their overall interactive goal and social engagement. While these assumptions are currently not realized in our MT prototypes, we believe they can become feasible, and they are useful in allowing us to consider the design of MT's interactive scenarios. Fig. 5 shows some examples of MT's fundamental potential applications. As shown in Fig. 5 upper row, MT's approaching movement can invite a specific person (e.g., a shy or reluctant user) and provide her with access to a digital workspace at her position. MT also can keep the workspace close to a moving person by following their movements or moving out of her way when the interaction is over by avoiding movements. Fig. 5's middle row shows basic usage examples of a single MT working with a group of people. Similarly to the single user case, MT's approaching and avoiding movements affects the group's physical workspace, and may change their task-flow and group dynamics. For example, MT's centering movement between two people can physically emphasizes their work or conversational space, providing a shared physical and interactive surface, or MT clearing the shared space can indicate the ending of a task. Following, MT's movements, if supported by sufficient situational awareness of the group (e.g., [START_REF] Drury | Awareness in human-robot interactions[END_REF][START_REF] Marquardt | Proxemic interactions: from theory to practice[END_REF][START_REF] Marquardt | Cross-device interaction via micromobility and f-formations[END_REF]) can assist and augment face-to-face collaboration. to provide a wide and shareable interactive display for a large group of users, or break away to provide individual workspaces when users are engaged in different tasks or require privacy. We envision that these MTs' movements can be actuated by user's explicit commands, by implicit inputs like proxemics and F-Formations, or autonomously based on the task phases.

In summary, MT's autonomous movements, given sufficient situational awareness, can physically create and change its users' workspaces adapting them according to the task-flow, and potentially helping users improve task efficiency, allowing them to feel more comfortable during different phases of a dynamic task. The following sections describe our exploratory evaluations of the fundamental attributes of MT, how MT's movements are recognized by users based on the motion cues, and how users spatial behaviors and space awareness are impacted by MTs basic movements.

Understanding of MT's Motion Cues

We conducted two observation studies to investigate whether tabletop users can infer, understand and socially relate to MT's basic movements based on its motion cues.

The first study focused on MT's straight movement and examined whether observers could anticipate MT's locomotion intention based on the motion cues it displays. The second study investigated whether observers can infer the social essence of MT movements. We used single MTSr for both of observation studies, allowing participants to perceive MT's movements along with their associated motion cues.

Study1: Linear Movement

Goal Our first study was set to examine if MT's motion cues are comprehensible, and whether they can help people anticipate MT's locomotion intent prior to its actual movement.

Method This study was conducted in a 5m x 5m experimental room. We recruited fourteen participants from the local university (six male, eight female, average age: 21.9) who were not informed of MT's locomotion capabilities. We used two MT's conditions in a within-subject design study: animated motion stylization (AMS); and MT without the motion stylization for baseline, presenting a static image while its moving (SI). The order of the conditions was counterbalanced. For each condition, MT displayed the visual content shown in Fig. 3, and moved back and forth twelve times along a 3 m straight line. Each participant observed the movements from approximately one meter away from the line-of-movement. Afterwards each answered a questionnaire about MT's movements using a 5 Likert scale (1: disagree, 5: agree), and was interviewed.

Result and discussion

We confirmed the overall tendency of the obtained Likertscale data fits normal distribution and analyzed the data with one-way ANOVA. Unsurprisingly, MT's motion cues made sense to participants, and they reported understanding the coupling of the animated visual content with the table's physical movement and movement intentions in the AMS condition compared to reporting inability to infer MT movements in the SI condition. More interestingly, participants reported higher awareness of the screen visual content in the AMS condition (4.57 when answering "I paid attention to the screen") than in SI condition (3.43) (p < .05). They reported surprise when MT moved for the first time in both conditions, with average rating of 2.71 and 3.42 for AMS and SI respectively (p > .05), meaning that AMS did little to diminish the surprise effect of an interactive tabletop move for the first time. Overall the results show that MT's animated motion stylization significantly prompted users to look at the screen content, and helped them infer the table's movement and its direction prior to the actual movement. When asked to reflect on the AMS motion cues, most participants remembered the first three phases (Fig. 3a-c), and could map them to the metaphor of crouching to set before starting to move. Particularly, participants liked the arrow-shaped Go stylization (Fig. 3c), which received a relatively high score of 3.58 when answering "I felt that the animated screen content supported the table physical movement". While the Stop phase (Fig. 3d)) was successful in reflecting MT's reaching its end of movement (4.07 for AMS), the relax phase (Fig. 3e) was less effective in expressing that MT relaxes, with AMS of 1.86 for "I felt the table becomes relaxed when it stopped." while SI was 1.36 (p > .10).

During the interview many participants reiterated that the integration of physical and visual elements on MT was providing efficient cues for the table's movement intentions. The interview provided many positive comments on MT and on its use of AMS: e.g., "funny", "interesting", or "useful device that extends classic furniture".

Study 2: "Social" Movements

Goal Our second observation study examined how observers recognize and understand MT's basic social behaviors when it was moving by itself, or when it was moving in relation to actors. This study was conducted with identical experimental setting and with MT providing AMS motion cues in all the conditions.

Method

Ten participants (four males and six females, average age: 22.5) in a within-subject design following six MT movement conditions. Participants were not informed of MT's locomotion capabilities. In every movement condition, participants were asked to observe MT's movement for 30 seconds from 1 meter away from the movement range. Participants were then asked to reflect on their experience via a GodSpeed questionnaire [START_REF] Bartneck | Measurement instruments for the anthropomorphism, animacy, likeability, perceived intelligence, and perceived safety of robots[END_REF], reflecting on five HRI perceived aspects of a robot: anthropomorphism, animacy, likability, perceived intelligence, and perceived safety. We used GodSpeed, a standard qualitative HRI evaluation tool, in order to evaluate user's perceptions and social acceptance of MT's social movements, and to reflect on how these can scale to the perception of MT as a social agent. Each dimension was evaluated using 5 points scale. Some of MT's movements were done in relations to actors; the six conditions were presented in a customized counterbalanced order among participants. Below we outline the different MT's movements examined in the study:

Stand -MT was located at the center of the room, not displaying any visual content on its surface and not moving.

Move -MT displayed a static image on its surface and moved randomly within the room.

MT Move -MT randomly moved within the room while displaying motion cues.

MT Following -MT automatically followed an actor who was walking freely in the room (MoCap tracked). It was demonstrated several times for duration of around 30 sec. (Fig. 6a).

MT Centering -MT located itself, with motion cues, at the central position between the two actors, simulating a basic social behavior of MT suggesting its physical workspace to collaborating users. It was demonstrated several times for duration of around 30 sec. (Fig. 6b).

MT Avoiding -MT continuously kept away from the moving actor as long as possible within the room (Fig. 6c).

In all six conditions MT's initial location was at the center of the room and its MT's movements were initiated by the actor's movements.

Result and discussion

In addition to the Godspeed HRI questionnaire, we also asked participants to reflect on their understanding of MT's movements by selecting descriptors from six candidates. Overall, as we expected, participants correctly understood the meaning and intentions of MT's social movements. For example, MT Following condition was accurately judged as "Table is following a person" and MT Centering condition was correctly recognized as either "Table is following" or "Table is approaching to be used". On the other hand, MT Avoiding condition was not always (5/10 participants) recognized correctly by participants. The reason could be that participants were less inclined to infer an unhelpful movement of a tabletop interface escaping its user, or from lack of agility in the MTSr movements when trying to avoid the approaching actor.

We confirmed normal distribution of the obtained 5 scale data and used one-way ANOVA and Bonfferoni test to compare the average scores of the six conditions for each GodSpeed dimension. For anthropomorphism, the overall scores for all conditions were less than the neutral (e.g, 2.1 for Stand, 1.7 for Move, 2.5 for Animation and MT Move, 2.7 for MT Avoiding) while only the MT Following condition provides a high score of 3.4 (with significant difference than Stand and Move). This result reflected on overall weak perception of MT as having human-like attributes. Animacy is the property of alive agent. This showed that the three social movements, MT Following, MT Centering, and MT Avoiding gave significantly higher scores of 3.7, 3.6, 3.5 respectively, than others. Similar perceptions were found in the interviews, for example, "like creature" "The table was suggesting its workspace". For likeability, MT Following (3.7) and MT Centering (4.0) had substantial high scores. Here, MT Centering had a significant difference against Move condition. In Perceived intelligence, we obtained similar tendency to the Likeability in which the scores of MT Following and MT Centering were larger (sig. diff than Stand). The dimension of Perceived safety offered complex results, our brief summary shows that the static conditions were judged as stable, calm and quiet while only MT Avoiding, a social movement was negatively perceived as rough and supersize. This can be also explained by the clumsy movements of MTs in this condition, which can also be fixed with minor technical improvements.

In summary, the basic social movements of MT were recognizable by participants. Also, from Godspeed, the MT Following and MT Centering were perceived as socially acceptable with the impressions of intelligent agent, likable and safe. This is an interesting finding that shows MT can be adopted to various social settings.

Impact of MT on Interaction and Collaboration

The two observation studies established an understanding of two important aspects of how people perceive MT's movements. We were also interested in exploring how users behave and change their interaction flow in order to adapt to the dynamically changing workspace afforded by MTs. Therefore, we conducted two interactive studies (study 3 and 4) that asked participants to perform a collaborative task with a partner using MT, allowing us to probe some of the social and collaborative aspects of interaction with a moving interactive tabletop. MTJrs were used for studies 3 and 4 because they incorporated a more sensitive multi-touch display, and their compact enclosures was more convenient, stable and safe when investigating MT's movements during user interaction.

Our two interactive studies were designed as an early reflection on the interaction scenarios described in section 4, taking a simplified approach to reflect on some of the fundamental aspects of group interaction with automatically moving tabletop interfaces. While the participants were asked to perform valid tasks on the tabletop, MT's movements were basic, and initiated by a simple WoZ [START_REF] Riek | Wizard of Oz Studies in HRI: a systematic review and new reporting guidelines[END_REF] algorithm.

Study3: Single MT Single User

Goal This study examined how the movement of a single MT can impact interaction. MT performed a set of basic movements, but this time with a participant being part of the interaction scene, not merely observing from the sidelines.

Method

Twelve participants (8 males and 4 females, average age: 21.8) from local universities participated in this study, which took place in the same experimental room as studies 1 and 2. Participants were provided with a simple MT-based tool and a generic picture browsing task: MT displayed an interactive picture browser that allowed participants to browse pictures presented on the tabletop surface. The browser (Fig. 2b) consisted of two views: pictures thumbnails were shown at the left half of the screen, while the right half presented a preview window showing a larger version any of one of the thumbnail pictures. The interface was populated with twenty contemporary pictures relating to popular topics such as sports, politics, and hobbies. The participants could select any of the thumbnails which will in-turn populate the preview window.

Participants were not provided with any specific instructions on how to use the tool, or MT and were Mo-Cap tracked as they moved through the experiment room. Each task was short, around 40 seconds long, allowing the participant to engage with the tabletop task and with a different movement by MT. This study was conducted with a within-subject design that examined impact of the following MT's movement conditions; static, approaching and avoiding (Fig. 7). The order of the conditions was counterbalanced among participants. All the MT movements in this study included motion cues on its display. The three conditions below were run by the study administrator using a simple WoZ algorithm. The three conditions below were run by the study administrator using a simple WoZ algorithm. The conditions and method of this study were based on the basic movements of MT shown in Fig. 5's upper row where MT is approaching a person in order to engage her in interaction or MT is avoiding the participant, disengaging from interaction.

Static -A reference condition; MT was located around the center of the room, and remained static, running the picture browser tool on its surface (Fig. 7a).

Approaching -MT was initially located around 2 meters off the room center. Ten seconds after the task started MT initiated approaching movement, towards the center of the room and the participant (Fig. 7b).

Avoiding -MT was initially located at the center of the room. Ten seconds after the task started, MT initiated a movement away from the center of the room, and the user (Fig. 7c).

Results and discussion

The qualitative analyses were performed based on questionnaire asking participants to rate their experience using a 5 scale Likert. We also conducted a post-interview and a grounded theory [START_REF] Strauss | Basics of qualitative research techniques and procedures for developing grounded theory[END_REF] video coding behavioral We coded the participants' spatial actions and behaviors, reflecting on the three movement conditions and analyzed our coded events by a comparative analysis relating to our control factors. We compared the coded events numbers in relation to the movement condition in which they occurred and the timing of the event relatively to the movement (i.e., before, during and after table movement). Below we briefly highlight our main findings regarding participants' spatial behaviors: -All participants approached MT. About 30% of the participants followed MT's in its avoiding movement. -Following MT's movement, participants frequently moved and looked around.

-All participants touched MT's surface and interacted with the tabletop picture browser significantly more after MT's movement compared to before its movement (in touch/min). -Some participants were visibly surprised with MT's first movement, but this effect disappeared in the following movements.

Generally, and surprisingly to us, our statistical analysis of questionnaire results were overall flat: participants remained relatively neutral, or just below neutral, regarding their MT experience, and there were no meaningful differences in ratings between the conditions. From interviews, a possible explanation for these findings emerged: participants who were left alone with the moving MT were not sure about the purpose of the task, which lacked by design social context. Several potential applications were suggested in the interview, for examples a "seller robot", "domestic robot for elder persons", or that MT will be "useful in hospital, classroom, and office meeting" etc.

Summary. The video coding showed that participants interacted with the visual content on MT's surface, and that their interactions with MT were significantly altered after MT's movement occurred, causing people to follow MT spatially, and interacting more with its tabletop interface. Although all participants accepted that MT had potential, the questionnaire results did not indicate clear differences between MT's movement conditions. Our assumption is that when evaluated by a single user in the current study setting and thus taken out of the collaborative context, MT becomes 'just' a robot, a perception which diverts from the social role it was design to serve, helping a group of people as a dynamically moving and changing interactive surface. While we do not argue that the results of single MT with a single user are not valid, they do highlight MT limitations, and point to its true potential serving a group of collaborative users, which we explore in the following study.

Study 4: Multiple MTs Multiple Users

Goal Our 4 th study was probing a more holistic MovemenTable vision: what will be the impact of a group of MTs who are dynamically changing users' interactive collaborative workspace? For simplicity, we studied synchronized physical connections and separations of two MTs and investigated how these movements affect Method Participants were the same group of 12 university students recruited for study 3, paired into six teams, and located in the same MT experimental settings (Fig. 8). The teams members knew each other. Based on their experience in study 3 team members were aware of MT's locomotion abilities, and knew how to use the interactive picture browser on its surface. This method allows us to see more realistic social experiences by multiple MTs movement in the study 4, rather than seeing fundamental or first-time reaction of the MTs' automatic movements, which was already observed in Study 3. We conducted a within-subject study with the following four conditions using a customized counter balance order among teams.

Connected -Two MTs were arranged side-by-side around the center of the room (Fig. 8a). Each display surface ran a standalone picture browser. MT remained static throughout the condition. Separated -Two MTs were placed 1.8 meters apart from each other (Fig. 8b). The distance was sufficient for participants to maintain privacy as they interact with MT. MT remained static throughout the condition.

Connecting -Two MTs were placed 1.8 meters apart (Fig. 8c) and started to move towards each other 30 seconds into the interactive task.

Separating -Two MTs were connected to each other at the center of the room (Fig. 8d) and departed to different directions of the room 30 seconds into the interactive task, stopping when they were 1.8 meters apart from each other.

The connecting and separating conditions allowed us to test how MT intentional dynamic changes to the workspace, moving from a unified large interactive space to two distributed smaller ones affect the collaborating users, reflecting on basic collaboration themes such as individual vs. collaborative, or private vs. shared data access. For each condition, participants were instructed to collaboratively create a story on the MT based on pictures they selected individually. The pictures followed a different theme for each of the four conditions (e.g., pictures relating to sports, hobby etc.), which were presented in a balanced order to the different teams. The task was completed once participants reported that their collaboratively created story is ready. This simple task was designed because we were interested in how users interaction, behaviors are affected MT's movement during typical collaboration that requires both touch interaction and some discussions with partner. The two dynamic conditions of connecting and separating included motion cues in all MTs movements.

Results and discussion

We probed the impact of the four movement conditions on participant's behaviors and interactions using a questionnaire, video coding, and postinterviews. Regarding analysis of questionnaire, we used ANOVA and Bonfferoni test for normal distribution data while we used Freedman test in the case that data does not have normality. Table 1 details how the different conditions were rated on the questionnaire, showing only questions (designated by Q below) that reflected significant difference between the movement conditions. The results demonstrate that most participants thought of following the MTs movements (Q1), and were affected by the changes of their collaborative workspace due to MT movements. For example, MTs connecting guided the two participants to spatially get closer to each other, spatial behavior that could trigger discussion of the task within the team (Q2). On the other hand, the MTs moving away from each other would cause participants to finish their chat (Q3). Participants were collaborating closely on their team tasks in the connection and connecting conditions (Q4) while separation from their partner caused them to pursue a separate task, for example picture browsing on the tabletop instead of the requested story composition (Q5, weak effect). Q6 showed an interruption effect by MTs. The separating and connecting conditions disturbed team collaboration; however, this negative effect was arguably not high, with ratings close to neutral.

In the video coding, we compared the number of participants' spatial actions to the movement condition in which they occurred, and to the timing of the event relatively to the movement (i.e., before, during and after MT movement). Our main findings are:

-All participants approached MTs and touched their surfaces during collaboration.

-About 70% participants followed the MTs' movements and changed their positions accordingly. This is encouraging since we did not provide any instruction on the MTs movements or on how to react to them. The participants that did not follow "their" MT when it separated remained with their teammate's MT, sharing it after it stopped its movement.

-While there was no accidental collision between participants and MTs. 16% of the participants had at some point to visibly back out of the MTs trajectory.

-Participants pointed their finger at the partner's table. This effect was more evident in connected and connecting, and grew more especially after the connecting movement in frequency of interactions, touch /sec.

-Frequencies of gestures such as nodding, hand waving, pointing and looking at the partner significantly increased after the MTs separated.

Summary

The collaborative workspace was significantly influenced by the MTs' physical connecting and separating movements, strongly impacting the collaborative and spatial behavior of participants. Our findings suggest that MTs' connecting can lead a more focused collaboration in a shared space, allowing teams to work closely together on a task, possibly so than in the connect condition with its preexisting larger surface. MTs separating on the other hand led to a more individual work style, with teams keeping apart and focusing less on their collaborative task. While this influence was generally perceived positively it is important to note that our study was not done on a naturalistic settings, and it remains to be seen how MT's movements will affect users in actual workspaces.

A technical limitation emerged from MT's physical bezels limited the ability of two MTs to connect into a single unified and unobscured surface. A study design limitation was recruitment of our participants who are aquatinted. On one hand, this is a clear bias, on the other; it did allow us to observe more natural and dynamic collaboration in the study teams. Given the preliminary nature of our study, being the first examination of multiple moving interactive tabletops with multiple users, we preferred this approach, but it leaves the question of MT's potential social impact on users who do not know each other unanswered.

Discussion

All our prototypes, MTSr and MTJr functioned well in our four WoZ studies, moving around the environment, tracked and controlled with the aid of a MoCap system, providing continuously the interactive surface function, and the motion cues visualizations augmenting their movements. However, more work needs to be done to improve the technical aspects of MT: using a bezel-less tabletop, allowing seamless merger of several MTs, improving MT's motion agility to support more accurate movements during multiple MTs synchronization, and developing algorithms for autonomous and safety MT behaviors.

We are quite satisfied with MT's motion cues technique, using the tabletop visual content as an implicit animated character according to MT's movement. People found MT's non-verbal motion cues helpful and were successful in inferring MT's movement intention, direction and distance based on its squash-and-stretch and speedlines motion cues. Using of the tabletop content to create animated motion cues maintains continuity of content on the tabletop surface, and does not move too far from the metaphor of an interactive tabletop, which may not be the case if the tabletop will provide motion cues using voice or physical robotic arms waving. We are planning to explore the abundance of other expressive motion cues, inspired by the rich possibilities afforded by cartoon art and animation.

Our interactive studies demonstrated that multiple MT's movements had strong impact on user's spatial behaviors and interactions. This effect was most impressive in synchronized movements of multiple MTs in collaborative scenarios. These finding are encouraging and point to the potential contribution MTs can have on affecting and guiding social and collaborative interactive settings. While our current findings are limited to WoZ experimental settings, the potential shown through our studies offer several steps and directions of future work. It would be interesting to explore practical performances of MTs in a targeted context by comparing with manually moving tabletop (e.g., [START_REF] Tandler | ConnecTables: dynamic coupling of displays for flexible creation of shared workspaces[END_REF]). We also plan to explore MTs autonomous control by leveraging situational awareness tracking technologies, instead of the WoZ study. Based on study 4 findings we are able to pursue larger and more complex MT spatial arrangements for example moving beyond simple connections to L-and U-shape table arrangements, deploying MTs in large spaces and social functions, applying more advanced algorithms, such as flocking, for grouping/ungrouping of a large number of MTs, and providing MTs with tools for better situational group awareness of their environment and users.

Finally, we are hoping to assess MTs' effect more and more in the wild, following at the beginning a few simple scenarios. Grabbing attention of passersby and enticing to interact is a fundamental challenge in interactive public displays. While our work still stop shorts of introducing automatically moving interactive tabletops into realistic public settings we think that MT has the potential to provide a novel solution to this basic public display challenge.

Conclusion

We presented an exploration of MovemenTables (MTs), moving interactive tabletops designed to affect their workspace and collaborative settings by changes to their spatial position and arrangement. We implemented two types of MT prototypes and designed animated tabletop content as motion cues that help MT users infer the tabletop locomotion intentions. We evaluated the prototypes via a set of user studies, based on several simple interaction scenarios. Our findings demonstrate that moving interactive tabletops can be accepted by users, and can influence their spatial behaviors. Our studies of a group of MTs also suggest that MT's fundamental movements, such as approaching a user, centering between two collaborating users, or connecting and separating have substantial impact on users' spatial behaviors and on their workspace awareness. The current findings motivate our future MT effort towards designing and testing more realistic collaborative scenarios. As part of our future work we will be designing proof-of-concept MTs that will guide users interactions and will probe the impact the dynamically changing interactive surfaces' location and size have on the collaborative task and the quality of the interaction

Fig. 1 .

 1 Fig. 1. MovemenTables

  (a) MovemenTable Senior (b) MovemenTable Junior and its tabletop view

Fig. 2 .

 2 Fig. 2. MovemenTable prototypes

Fig. 3 .Fig. 4 .

 34 Fig. 3. Motion cures by animated tabletop content

  As soon as MT reached its destination it physically stops, with its visual cues showing a squashed animation of the visual content, with the screen leisurely stretched back to its full screen version, in a 2 sec animation.

Fig. 5 '

 5 s lower row presents a simple example of how a synchronized group of MTs can support users' collaboration. For example, two or more MTs may connect in order MT Approaching Providing workspace MT Avoiding Clearing space MT Following Keeping workspace MT Centering Providing physical space MT Centering + Approaching Inviting person to the workspace MT Avoiding Clearing space MTs coupling Sharing extended collaborative workspace MTs separating Providing personal private workspace

Fig. 5 .

 5 Fig. 5. Interaction scenarios of MovemenTables

Fig. 6 .

 6 Fig. 6. MT social movements in study 2

Fig. 7 .

 7 Fig. 7. Single MT interactive study

  the MTs. The purpose of this study is also to understand basic effects of MTs by using a simplified WoZ study design with timedmovement of MTs during users

Fig. 8 .

 8 Fig. 8. Multiple MTs for multiple users study

Table 1

 1 Study 4 questionnaire results.

		Question	Condition	Score	Sig.
	1	I wanted to follow the table	Connected Separated Connecting Separating	1.4 1.9 4.1 4.2
	2	I thought to start talking with partner	Connected Separated Connecting Separating	2.7 2.9 4.1 3.5
	3	I thought to finish talking with partner	Connected Separated Connecting Separating	1.5 1.2 1.3 2.4
	4	I thought to do the task together	Connected Separated Connecting Separating	4.5 3.4 4.1 3.3
	5	I thought to do the task separately	Connected Separated Connecting Separating	2.3 2.8 2.2 3.3
	6	The table movement disrupted our task	Connected Separated Connecting Separating	1.3 1.3 2.4 3.6

Acknowledgments. This work was supported in part by JSPS KAKENHI Grant Number 26730101, by an NSERC Discovery Grant, and the Cooperative Research Project of the Research Institute of Electrical Communication, Tohoku University.


Laura Cortés-Rico

Giovanny Piedrahita-Solórzano

Participatory Design in Practice

Keywords: Participatory Design, Crafts, Embroidery, Representation, Dialogue, Recognition, Tangible User Interfaces and Social Technologies

Introduction

Pérez-Bustos and Franco-Avellaneda outlined the idea of designing an ICT inspired by embroidery as an approach to enhancing embroidery as it is practiced in Cartago, Colombia [START_REF] Pérez-Bustos | Embroidering Self-knowledge: Systematization of Experiences and Participatory Design of Weaving As a Caring Practice in Cartago, Valle, Colombia[END_REF]. They presented their intention to reinforce the making of embroidery as "an expression of caring practices aimed to build self-knowledge." Although Cartago is nationally recognized for its embroidery, the embroiderers themselves experience precarious conditions and their craft is often an informal and secondary labor. Because of this, Pérez-Bustos and Franco-Avellaneda proposed that ICT could be an appropriate tool to make the artisans' material conditions and core skills more visible to those unfamiliar with this kind of craft work.

The creation of such a social ICT implied a project developed using a participatory design (PD) approach, to make possible the "dialogue between technological knowledge and different kinds of traditional wisdom" [START_REF] Pérez-Bustos | Embroidering Self-knowledge: Systematization of Experiences and Participatory Design of Weaving As a Caring Practice in Cartago, Valle, Colombia[END_REF]. PD not only means involving the prospective users of a new technology in specifying requirements, and testing and gathering reactions to it, but giving users the role of co-designers. Choosing a PD approach for the project implied taking into account the care practices and the moral and pragmatic issues outlined in [START_REF] Pérez-Bustos | Embroidering Self-knowledge: Systematization of Experiences and Participatory Design of Weaving As a Caring Practice in Cartago, Valle, Colombia[END_REF]. According to Carroll [START_REF] Carroll | Participatory design in community informatics[END_REF], users not only have the right to be included in the design process (moral proposition), but their inclusion leads to a more successful outcome (pragmatic proposition).

This project, "Embroidering self-knowledge: Systematization of experiences and participatory design of weaving as a caring practice in Cartago, Valle, Colombia"1 , began in January 2014 and will take two years. It is focused on calado, a particular type of embroidery made in Cartago2 . It involves the participation of a group of people with diverse forms and areas of knowledge: the authors -electronic engineers-, ethnographers, software and information professionals, a collective of caladoras (embroiderers), fashion designers and educators. As the various research team members came to the project with different notions about PD, it was necessary to establish basic concepts and understandings at the start in order for the activities to be meaningful and successful. This included coming to a common understanding of PD concepts and adapting our ways of communicating and engaging with the other members.

In this paper we present the development of the project, which had an emphasis on engagement through doing. We outline how we achieved participation by involving ourselves in the others' and our own practices, and how this participation led us to a knowledge dialogue between tradition -embroidery-and innovation -technology-. This technological design was strongly related to activity theory [START_REF] Kaptelinin | Activity Theory[END_REF] and phenomenology [START_REF] Winograd | Understanding Computers and Cognition: A New Foundation for Design[END_REF] as the theoretical foundations. Firstly, this was because of the continuous subjectobject interactions that we were involved in, mainly in hands-on workshops, and secondly, because of the central role of our bodies, through which we explored, learnt, dialogued, and recognized the practices of the communities involved in the design.

Guidelines

The moral and pragmatic issues of the PD process set a very strong guideline for the team: each member had to become involved in the knowledge domain of the others. This involvement entailed the design of activities to learn calado techniques, the design of patterns, as well as basic concepts of electronics. Sabiescu and Memarovic [START_REF] Sabiescu | Participatory Design for Cultural Representation: A Cultural Transparency Perspective[END_REF] outline the potential challenges facing PD processes, some of which our team encountered: a knowledge gap between participants, renegotiation of design methods and reformulation of design goals, as well as the challenge of defining common boundaries for all of the research team and enabling the caladoras community to become conscious of their role as peer participants in the research.

Coping with these challenges implied reconfiguring our ideas about the design of technology, because of the many heterogeneous actors identified in the process who played a dual role, both as potential users and as designers of the technology. Configuring the project to give responsibility to users was important in order to make sure that the designed technology would have a real impact and would lead to new ways of conceiving the practices both of making embroideries and of designing technology [START_REF] Gonzalez | Responsibility in User Participation in Information Systems Development[END_REF]. As a result of this configuration, three strongly articulated processes were established in order to achieve a successful PD: self-and mutual recognition, dialogue and representation.

─ Self-and mutual recognition. This indicates the process whereby each member of the team reflects on and comprehends who s/he is and what s/he does, and who each other member of the community is and does; this leads to the realization of what can be done as a single community. ─ Dialogue. Within the team, participants in each knowledge area have their own codes with which to represent what they do and know, and to communicate effectively with their peers; for example, software modeling languages in the developers' community. Dialogue in a PD process, however, should allow each member to communicate ideas in a common language for all the team, and then find convergence points where all of the participants have the same core understanding. ─ Representation. This process is possible when the participants are able to suggest and discuss design ideas because they have a sufficient interpretation of the others' and their own knowledge. It implies wishing and giving form to ideas as tangible objects that reflect diverse opinions, and are relevant and useful for the communities involved. It also means finding suitable ways to present them to others.

Participatory design in practice

In our context, PD was achieved through a methodology that included a series of activities aimed at facilitating self-and mutual recognition, dialogue and representation. These activities allowed the encounter between diverse actors at different moments of the project. In addition, these encounters allowed the co-creation of innovative and culturally representative artifacts.

Methodology

Methodologically, this project was organized using four iterative, incremental and open-ended milestones to achieve a successful technological design: recognition and reflection, ideation, prototype and experimentation (Fig. 1). Iterative means that the design process requires more than one cycle of going back and forth, and that there is a connection between milestones. This connection implies that there has to be reflection on all ideas prototyped and experimented, which includes recognizing how the different stakeholders react to prototypes and how this reaction reshapes the research. Incremental in this case does not refer to an incremental artifact, but to an incremental way of better representing the communities involved in the design. It means that the greater the immersion in the project, the easier it is for ideas to become culturally relevant artifacts. The step between one cycle and the next occurs when the design sees a significant change: an addition or removal of previous ideas; or the outcome that some ideas are justifiably swept out of the boundaries of the project, or new ideas are swept in [START_REF] Midgley | The Theory and Practice of Boundary Critique: Developing Housing Services for Older People[END_REF]. Ideas swept out of the project boundaries may become counter-examples, helping to recognize issues within the communities or the technology itself. Finally, aiming for open-ended milestones considers that results are not just finished artifacts but an empowerment of the community, which eases the appropriation of the designed technologies and the local development of new sustainable social technology. Empowerment and appropriation lead to a process of continuous design while the artifacts are being used [START_REF] Orlikowski | Using Technology and Constituting Structures: A Practice Lens for Studying Technology in Organizations[END_REF].

Fig. 1.Methodology followed in participatory design

Milestones

─ Recognition and reflection implied continuous active observation and receptive listening, involvement in one another's practices, as well as analysis of related work. This was accomplished through ethnography, hands-on workshops, surveys, meetings and informal chats. Through ethnography, the academic community recognized that in Cartago, calado embroidery and design are understood as completely separate forms of knowledge. Calado is usually associated with tradition and commonly used and done by elders, while design is related to young people and innovation. This recognition was the motivation for creating a technology that could bridge the gap between the design and making of calado. ─ Ideation was based on desiring, proposing, discussing and negotiating ways in which technology could be woven into the context. In this case, we travelled through many ideas, from the desire for an artifact in order to smell, taste and listen to embroidery patterns, to more realistic ideas such as representing stitches in a way that would allow users to explore new possibilities with them. ─ Prototype refers to the act of giving form to ideas. This form is a representation of an idea that allows people in the team to express, communicate, share, manipulate, modify, transform and discuss thoughts [START_REF] Watson | Listening in the Pakal controversy: A matter of care in Ancient Maya studies[END_REF]. In our project, one of the engineers had the idea that a calado stitch could be expressed as a drawing. The resulting prototype was a set of sketches made with different color pencils representing physical constraints of the materials, as well as the form that this stitch would have in an embroidery. ─ Experimentation indicates the scenario in which prototypes were manipulated by all members of the team. This milestone is mainly focused on sensitizing participants to use their hands to explore, learn and test prototypes, and is thus strongly connected to reflection [START_REF] Kaptelinin | Activity Theory[END_REF][START_REF] Winograd | Understanding Computers and Cognition: A New Foundation for Design[END_REF]. In relation to the prototype mentioned above, when embroiderers experimented with the sketches they did not feel motivated to translate them into calado. They argued that though they could be embroidered as calado, they would not look like it. Reflecting on this, we realized that the novelty in calado is not in the design of new stitches, but in the way in which existing ones are combined.

Activities

The aforementioned milestones are ways of viewing the methodology, not of partitioning it. To illustrate this proposition, below we present some of the main types of activities developed in the project, which served the purposes of more than one milestone in a non-linear way.

─ Hands-on workshops were spaces where participating communities could interact through the making of some of their practices. They were focused on: i) allowing the academic community to recognize some of the processes involved in the design and craft of calado in Cartago, ii) allowing embroiderers to get in touch with some technological issues that are close to embroidery and distant to automation 3 , and iii) allowing the complete team to use the prototypes generated during the project. Hands-on workshops involved active dialogue, embodied learning [START_REF] Klemmer | How Bodies Matter: Five Themes for Interaction Design[END_REF] and the manipulation of materials used by the different collectives in their areas of practice (Fig. 2).

─ Discussion sessions were spaces in which to talk about diverse issues surrounding the project. These sessions were aimed at socializing the systematization of the fieldwork, collectively clustering information, brainstorming, organizing incoming work and even telling anecdotes in familiar encounters. ─ External dialogues were activities where the team had encounters with other people and conducted research outside of the boundaries of the project. They allowed us to know about and connect to related work, to talk to experts in knowledge areas not present in our team, to share the advances of our research and to listen to external opinions.

Fig. 2. E-embroidery workshop: using embroidery and electronic materials like conductive thread, we embroidered a crafted Christmas manger with illumination and interactivity.

Results

We consider that the process of designing technology in a participatory way constituted a result in itself. Two main achievements support this statement: i) embroiderers managed to be less afraid of technology and to think of convergence points between embroidery and technology that are different to automation, and ii) technology professionals recognized the potential, complexity and transformative capability of knowledge associated with embroidery. Another result are the two technological artifacts that represent us as communities involved in the design. The first is a lighted embroidery hoop designed in recognition of the delicacy required to embroider calado, a craft that cannot be done with poor illumination. This artifact represents an innovation in the process of making embroideries in Cartago and has modified -and been modified by-the ongoing practices of embroiderers: to avoid shadows cast by the embroiderers' hands on the fabric, craftswomen started to use the hoop upside down, so having the light on top (Fig. 3A). The second artifact is a Tangible User Interface (TUI) that mediates dialogue between fashion designers and caladoras in the process of designing calado patterns. This TUI represents our recognition of the need to reduce the aforementioned gap between the design and making of calado, and a way of reinforcing and making visible the embroiderers community.

The TUI has two components: digital and physical. The digital one is a computational representation of stitches; its development required an embodied learning of calado [START_REF] Winograd | Understanding Computers and Cognition: A New Foundation for Design[END_REF][START_REF] Klemmer | How Bodies Matter: Five Themes for Interaction Design[END_REF], continuously doing and undoing the labor with our hands, and developing a close relationship with materials from both calado and electronic development [START_REF] Kaptelinin | Activity Theory[END_REF] (Fig. 3C). The physical dimension of the TUI represents our comprehension that a new calado pattern emerges from combinations of existing stitches, and not from new ones. In this sense, with the TUI components, a fashion designer can take a tangible stamp to print a representation of a stitch onto the digital representation of the fabric shown on a tablet (Figs. 3C &3D). The most interesting part is that after many prototypes, the technical solution for tangibles was literally embroidered: we used conductive thread to embroider tags on the stamps, making them recognizable on the capacitive screen using pattern recognition algorithms (Fig. 3B).

Reflections and conclusions

Participation was accomplished to the extent that dialogue between the different communities in the research project was achieved. A horizontal dialogue allowed negotiations and tensions to be easily translated into design decisions. Our most significant dialogue was non-verbal and took place mainly in the hands-on workshops. These activities were focused on self-and mutual recognition, and on seeking the participatory creation of representative artifacts. We also realized that the design was incrementally achieved by thinking ideas collectively, giving them a form, experimenting with them and then reflecting on the process.

Actively involving communities facilitates their empowerment, their appropriation of designed artifacts and also makes possible the local development of new sustainable social technology. Giving embroiderers and fashion designers the role of co-designers offered a more realistic interpretation of the way in which technology involves users: through use, artifacts both modify and are modified by ongoing practices [START_REF] Orlikowski | Using Technology and Constituting Structures: A Practice Lens for Studying Technology in Organizations[END_REF]. The plurality and heterogeneity within and between the participating communities in our project led us to conclude that PD does not necessarily imply the complete involvement of all actors in every task, all the time. Limited resources, geographical distance and specialized languages make such participation impossible.

Instead, we argue that recognition, dialogue and representation, as presented in our work, are key elements for collectively materializing relevant artifacts as synergies of multiple kinds and forms of knowledge.

We found out that crafts and technology design share a material dimension in which interacting through doing makes possible the creation of representative artifacts. This creation is achieved when each member is involved in the practices of other collectives within the research team, which generates connections between tradition and innovation, enriching craft without replacing the human role. In our project, getting involved in one another's practices enabled engineers to be more reflective about the complexity of the knowledge in the hands of embroiderers, but also revealed to caladoras connections between their knowhow and technology that differed from automation. These results may encourage the replication of the presented process with other craft communities, as a way of bringing innovation into their own processes and products.

Fig. 3 .

 3 Fig. 3. A. An embroiderer using the lighted embroidery hoop upside down. B. Embroidered tangibles with conductive thread used to stamp digital representations of stitches onto a capacitive surface. C. A simple calado pattern designed with the TUI. D. A user stamping a stitch onto a smartphone screen.

Funded by COLCIENCIAS, Pontificia Universidad Javeriana and Politécnico Grancolombiano.

Calado is made by removing threads from a fabric with warp and woof and then embroidering the fabric again with new threads, typically of the same color as the original fabric.

Embroiderers were very afraid of technology because it was understood as a way of eliminating the craft through automation.


Ming Ki Chong
email: mingki@acm.org

Jon Whittle
email: j.n.whittle@lancaster.ac.uk

Umar Rashid

Chee Siang Ang

Cue Now, Reflect Later: A Study of Delayed Reflection of Diary Events

Keywords:

Diary studies require participants to record entries at the moment of events, but the process often distracts the participants and disrupts the flow of the events. In this work, we explore the notion of delayed reflection for diary studies. Users quickly denote cues of diary events and only reflect on the cues later when they are not busy. To minimize disruptions, we employed a squeeze gesture that is swift and discreet for denoting cues. We investigated the feasibility of delayed reflection and compared it against a conventional digital diary that requires users to reflect immediately at the time of entry. In a weeklong field study, we asked participants to record their daily experiences with both types of diaries. Our results show that users' preference is context-dependent. Delayed reflection is favored for use in contexts when interruptions are deemed inappropriate (e.g. in meetings or lectures) or when the users are mobile (e.g. walking). In contrast, the users prefer immediate reflection when they are alone, such as during leisure and downtime.

Introduction

Field studies that require the full-time presence of researchers are impractical to conduct. Researchers have therefore adopted the diary method as an alternative for recording everyday behaviors of participants [START_REF] Rieman | The diary study: A workplace-oriented research tool to guide laboratory efforts[END_REF]. The method relies on participants to capture events in situ as they happen, so it requires no researcher presence and the participants provide first-hand self-reporting of their experience. Two types of diary studies exist [START_REF] Carter | When participants do the capturing: The role of media in diary studies[END_REF]: feedback studies where participants answer predefined questions about events, and elicitation studies where participants capture media that are used as prompts for discussion in interviews.

Feedback studies enable researchers to capture immediate answers from participants. For example, in a study of understanding task switching and interruptions in the work place, Czerwinski et al. [START_REF] Czerwinski | A diary study of task switching and interruptions[END_REF] asked participants to reflect while they were working. This form of immediate reflection provides the benefit that diary data is not influenced by memory decay. However, the immediate reflection distracts participants from carrying out their main task [START_REF] Carter | When participants do the capturing: The role of media in diary studies[END_REF].

In elicitation studies, interviews are conducted at the end of the study. Detailed information may therefore be lost due to prolonged delay, and participants' emotional responses may change over a period of time [START_REF] Isaacs | Echoes from the past: How technology mediated reflection improves well-being[END_REF]. To help participants reconstruct their memories, researchers have investigated the role of different media (e.g. photographs, audio recordings, location information, and tangible artifacts) in diary studies [START_REF] Carter | When participants do the capturing: The role of media in diary studies[END_REF] and have used lifelogging tools to support recall and reflection [START_REF] Gouveia | Footprint tracker: Supporting diary studies with lifelogging[END_REF][START_REF] Kalnikaite | Now let me see where i was: Understanding how lifelogs mediate memory[END_REF][START_REF] Sellen | Do life-logging technologies support memory for the past?: An experimental study using sensecam[END_REF].

Researchers have proposed an alternative elicitation method for conducting diary studies on mobile phones [START_REF] Brandt | Txt 4 l8r: Lowering the burden for diary studies under mobile conditions[END_REF]. The intention is to lower users' burden by allowing them to only capture "snippets of information" via text (SMS), voicemail or pictures (MMS). The users then explicitly upload the snippets onto a server for revisiting later. The snippets serve as prompts for users to complete full diary entries at a later, more convenient time. We embrace this notion of delayed reflection: events are first triggered and stored as cues, and reflection is carried out during users' downtime.

We adopted SqueezeDiary, a delayed reflection diary tool that uses squeeze gestures for triggering event cues [START_REF] Chong | Squeeze the Moment: Denoting Diary Events by Squeezing[END_REF][START_REF] Chong | SqueezeDiary: Using Squeeze Gesture as Triggers of Diary Events[END_REF]. The application has several advantages. Squeeze is simple and quick to perform. The small form factor of the tactile sensor (see Fig. 1) enables users to squeeze it swiftly without the need for accessing the smartphone. Data is stored locally, so the system requires no explicit uploading of information.

In this paper, we present a comparative study between delayed reflection for elicitation and a conventional digital text diary that requires immediate feedback from users. We first present the implementation of the two diaries, and then report on our weeklong deployment of the diaries. The results reveal that users' preference in the type of diary is context-dependent. Participants reported that they would prefer to use delayed reflection for recording events when they are mobile (e.g. walking), in a social event (e.g. meeting with colleagues), or in a restricted context (e.g. attending a lecture). However, the participants would prefer to use the conventional text diary during their leisure and downtime. In this case, they can reflect and enter diary entries straightaway, so the process of triggering an event instance before entering a diary description becomes unnecessary.

Diary Applications

To learn the differences between immediate reflection versus delayed reflection, we studied the use of two digital diaries: a conventional digital text diary for immedi- We adopted SqueezeDiary [START_REF] Chong | Squeeze the Moment: Denoting Diary Events by Squeezing[END_REF][START_REF] Chong | SqueezeDiary: Using Squeeze Gesture as Triggers of Diary Events[END_REF] as an application for delayed reflection (see Fig. 2). A user first squeezes a sensor to trigger the system to record an event instance, and the user later enters a description for the event retrospectively. The application uses a small tactile ball as a squeezable user interface, and it interfaces with the smartphone through Bluetooth. The sensor device can be carried in a pocket, and users can squeeze it easily when needed, without accessing their smartphone. A user triggers an event instance by simply squeezing the sensor for two seconds, and the system automatically logs the location, the timestamp and the pressure levels. Our application provides visualizations of the recorded events on a timeline (2B) and on a map (2C). The application initially provides a graphical visualization of squeeze pressure, but we abandon it as a pre-study revealed that the pressure visualization provides no help for users to recall detail memory events. The application included an interface for users to add retrospective descriptions for their recorded events (2D), and a calendar interface for selecting recorded diary entries (2E).

For immediate reflection, users provide a textual description when they add a diary entry. We implemented a simplified diary application that has only two UI options (see Fig. 3). One option is for adding a new diary entry that automatically includes GPS location and timestamp (3B). The information serves as temporal and location cues to help the users to reconstruct their episodic memory [START_REF] Gouveia | Footprint tracker: Supporting diary studies with lifelogging[END_REF][START_REF] Kalnikaite | Now let me see where i was: Understanding how lifelogs mediate memory[END_REF]. The second UI option allows users to revisit and update their records (3C).

Diary Study

We conducted a weeklong field trial to compare the two diaries. We recruited 8 participants (3F), aged between 19 and 27 (M=22.25, SD=3.20). The participants were students at our institutions, from a variety of academic disciplines. They all owned a smartphone (either Android or iPhone) and self-rated as proficient smartphone users.

In the briefing we demonstrated the operations of both diary applications and also asked the participants to practice using the applications by recording sample diary entries. We explained to the participants that their task was to record instances of when they realized that they were not focusing or struggling to concentrate on their current task; for example, doing one thing but thinking about another. We selected this task because our target domains are well-being related applications, and the problem of 'doing one thing but thinking about another' is one representative of such applications. At the end of the briefing session, we gave the devices to the participants and instructed them to start recording on the next day. We also provided demonstration videos in case the participants encountered problems with using the diaries.

The recording lasted for six days. The study followed a within-group study design; half of the participants started with the squeeze diary and then switched to the text diary after recording for three days, and vice versa for the other half. During the recording period, the participants used the diary for the entire day; they started recording from the point they awoke until they retired in the evening. We instructed the participants to record instances only during weekdays when they were usually busy. To keep the participants engaged with the study, we sent an email reminder every evening [START_REF] Palen | Voice-mail diary studies for naturalistic data capture under mobile conditions[END_REF].

After recording for six days, we invited the participants back for exit interviews; each session lasted for approximately 30 minutes. We used the diary entries to prompt the participants on how they used the diary applications; we also elicited qualitative feedback, as well as suggestions for improvement.

Results

In total, our participants recorded 120 delayed-reflection diary entries (M=15, SD=10.70, Mdn=11.5) and 84 immediate-reflection diary entries (M=10.5, SD=6.65, Mdn=9.5). A Wilcoxon Signed-Rank Test did not reveal a significant difference in the number of entries between the two diaries (N(8), Z=-1.47, p>0.05). Two members of our research team analyzed the collected data independently.

Reflection: Immediate vs. Delayed

We observed two types of users. One type of users found it easier to perform delayed reflection, as it allows them to continue with their primary task with minimum disruption. These users enjoyed the freedom of entering diary entries "at [their] own pace". Some participants mentioned that they occasionally found it "challenging to reflect" on an event if it was recorded after a lengthy period or if they had a busy day.

For example, there was a day that a participant was busy for four consecutive hours (attending lectures and meetings), and she had squeezed the sensor several times. During her delayed reflection, a cluster of events was shown on the timeline which confused her. She clarified by examining the locations of the events, which helped her to differentiate whether she was in a lecture or in a meeting. Our participants described that seeing a cluster of events on a timeline made them realize how much they struggled to concentrate in specific events (e.g. attending "a boring lecture").

The second type of users that we observed preferred immediate reflection. These users could "only remember the gist" but forget the details quickly if the description was not recorded straightaway. One participant who had several part-time jobs mentioned that on a busy day he had to multitask frequently, so memories could overlap and detailed information could become vague if he did not record it immediately.

Our participants mentioned that when using the SqueezeDiary, they wrote a description immediately after they squeezed the sensor during their leisure, such as relaxing at home in the evening. In contrast, one participant used the mobile text diary for delayed reflection. He explained that he often switched his thoughts when he was changing venues between lectures, so he would not have enough time to reflect immediately and enter a description while in transit. He instead first started a diary entry with empty content, and then entered a detailed description later using the update feature.

Context Preferences

The participants preferred to use delayed reflection diary during busy working hours and in situations where using a phone was forbidden or considered inappropriate. The participants considered short notifications as acceptable (e.g. short vibrations or audio alerts on the phone for when an event cue is recorded), as it is similar to "receiving a text" message. However, taking out a phone and entering text would be deemed socially impolite (e.g. "rude to enter text in front of friends") or inappropriate during classes and lectures. The participants reported that they usually reflect on recorded events during their breaks (e.g. long breaks between lectures or lunchtime) and in the evening.

The participants also reported that they prefer to perform immediate reflection during their leisure or downtime (e.g. resting at home), when they were not bounded by work or duties, which gave them opportunities to self-reflect. The participants also mentioned that they preferred to write diaries when they were alone, as this eliminates distractions and social awkwardness. Some participants mentioned that if they were not busy it is more convenient to "just enter diaries", without needing to first squeeze a sensor to cue an event.

Overall, our participants disliked writing diary entries when they were moving. We learned that delayed reflection is good for recording instance of events during users' busy periods, while immediate reflection is suitable for leisure situations, as the action of first cueing an event before recording a description becomes unnecessary.

Visualization

Our participants explained that the act of squeezing prompted them to consciously remember particular thoughts, and later seeing the cues of the recorded events helped them to recall those thoughts. Visualizing the cues on a timeline and on a map helped the participants to disambiguate events. They did this by correlating their daily schedules with the visualizations.

User Feedback

We also elicited general feedback on usability, alternative uses, and suggestions for improvement. One participant said that he kept the tactile squeeze ball in his trousers pocket. The "bulginess" reminded him to squeeze for an event. This indicates that the physicality of the sensor can act as a reminder for users to record events.

The participants reported several issues of SqueezeDiary. On several occasions users could not record due to unstable Bluetooth connection between the sensor and the smartphone. Once a connection was lost, the users needed to reconnect the devices manually. The participants suggested automatic reconnection. Battery life is another issue: leaving the sensor connected could deplete the battery overnight, which required the users to recharge the sensor when they had the opportunity during the next day. The sensor occasionally recorded false data when it was left inside a bag or in a pocket. All of these indicate that the performance of the sensor is very important. Users are sensitive to inaccurate data; false positives or missing data could render the diary ineffective. This could be explained that people use the recorded cues for assisting their recall of memory events, so some information is already embedded in their memory, which makes spotting inconsistency easy.

Suggestions include using the diaries as a reminder for tracking daily tasks. The time and location cues could improve prospective memory [START_REF] Sellen | What brings intentions to mind? an in situ study of prospective memory[END_REF]. Suggestions for other memory aids include adding pictures and replacing text with voice narration, but some people reported that they do not like to listen to their own voices.

Post-Study Impact

After completing our study, two participants expressed that by reflecting on their recorded entries, they realized that they needed a better management strategy for multitasking. One participant noticed how much time she spent thinking about her work. Even during her downtime, she was constantly worrying about work. For instance, her diary entries include "I couldn't sleep ... thinking about how much work I need to do" (recorded at 4:24 am); and "packing my bags for a weekend away and thinking about whether I should with all my work". She explained that going through the diaries made her realize that she was consumed by her work and needed a break. Similarly, another participant also reported that seeing her own diaries made her "realize how stressed out [she was]".

Discussion

From the study we learned that delayed reflection is a suitable method for people to record diaries when they are busy or in situations when they could not reflect immediately. However, there exists a trade-off of detailed information for users' convenience. Detailed information could be lost because people's memory decays due to interference over time, especially when they experience a busy day or reflect after a long period. Our study showed that location and temporal cues helped users disambiguate events; however, other studies have shown that these cues are only inferential, and they are insufficient for reconstruction of finer details [START_REF] Kalnikaite | Now let me see where i was: Understanding how lifelogs mediate memory[END_REF]. For recalls of detailed memories, media elicitation techniques (e.g. recording visual cues) could be usefully combined. One way for this is to incorporate the diary application with a lifelogging camera (e.g. SenseCam [START_REF] Hodges | Sensecam: A retrospective memory aid[END_REF]). The event instances could then be synchronized with the camera data to provide rich media information to help the users reflect.

Our study revealed that people have different preferences between immediate and delayed reflection. We were surprised that our participants found novel ways to use our diary applications as the other type of diary (e.g. using the update feature of text diary for delayed reflection). Hence, there is no one method that fits all; designers should consider creating diary applications that allow users to do both types of reflection, and let users decide their preferred usage.

People often reflect while they were traveling, in transit between venues, and in traffic. We should design interfaces that allow people to easily record thoughts when they are on the move. For instance, a participant mentioned that accessing his mobile phone to record a thought while riding a motorbike would be impossible. He would prefer to have sensors embedded into his gloves and use voice for recording descriptions. With the proliferation of wearable devices, we envision that in the near future we could use body-worn devices to detect users' intents to record diary events.

While automated recording devices (e.g. lifelogging cameras) generate overabundance of information, our dairy enables users to choose the moment they want to record, and the users can do it discretely without comprising privacy.

The gesture for triggering event instances could easily be extended with multiple gestures for new interactions. For example, users can customize a particular gesture for work related entries and another gesture for family related entries, so event annotation could be done at the time of recording. Instead of using a squeeze ball, the system could adopt other devices, like a smartwatch that senses user gesture (e.g. tapping), to record event instances. Also, delayed reflection could be applied beyond the diary study method. The diary application has other use cases. For example, it could be applied as a site-tracking tool for people to keep track of where they have visited. This is particularly convenient for tourists who enjoy exploring new places. They can mark down any interesting places and later use the recorded cues to reflect on their journey.

Finally, our study recruited university students as participants; their daily activities mainly involved attending lectures and societal meetings. It would be beneficial to study whether delayed reflection helps workers (e.g. office employees) to reflect on their busy activities and find ways to improve their work-life balance.

Conclusion

This paper presented a weeklong in situ diary study that compared immediate reflection with delayed reflection. Our results show that people's preference is contextdependent. They preferred recording diary entries with delayed reflection during busy hours or when they cannot access their devices to provide a complete diary entry; however, the method became unnecessary during people's leisure when they are relaxed and alone.

Fig. 1 .

 1 Fig. 1. Interaction of the delayed reflection diary used in our study. (A) The squeeze sensor. (B) Squeeze to record a cue. (C) Review recorded event cues. (D) Diary entry. (Source: [3])

Fig. 2 .

 2 Fig. 2. Screenshots of SqueezeDiary, an implementation of delayed reflection.

Fig. 3 .

 3 Fig. 3. Screenshots of text diary, an implementation of immediate reflection.

Acknowledgement

This work is part of the Digital Brain Switch project and is funded by the EPSRC (EP/K025201/1).