Amsterdam University of Applied Sciences
Self touch to touch others
designing the tactile sleeve for social touch
Huisman, Gijs; Darriba Frederiks, Aduén; Heylen, Dirk; Van Dijk, Betsy; Kröse, Ben
Publication date 2013
Document Version Final published version Published in
Proceedings of TEI’13
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Citation for published version (APA):
Huisman, G., Darriba Frederiks, A., Heylen, D., Van Dijk, B., & Kröse, B. (2013). Self touch to touch others: designing the tactile sleeve for social touch. In Proceedings of TEI’13
Association for Computing Machinery.
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Download date:27 Nov 2021
Self Touch to Touch Others:
Designing the Tactile Sleeve for Social Touch
Gijs Huisman
University of Twente, Human Media Interaction Group gijs.huisman@utwente.nl
Dirk Heylen
University of Twente, Human Media Interaction Group d.k.j.heylen@utwente.nl
Adu´en Darriba Frederiks Amsterdam University of Applied Sciences, Digital Life Centre
a.darriba.frederiks@hva.nl
Betsy van Dijk
University of Twente, Human Media Interaction Group e.m.a.g.vandijk@utwente.nl
Ben Kr¨ose
Amsterdam University of Applied Sciences, Digital Life Centre
b.j.a.krose@hva.nl
Copyright is held by the author/owner(s).
TEI 2013, February 10-13, 2013, Barcelona, Spain ACM
Abstract
In this paper we present the concept and initial design stages of the TaSST (Tactile Sleeve for Social Touch).
The TaSST consists of a soft pressure-sensitive input layer, and an output layer containing vibration motors. A touch to ones own sleeve is felt as a vibration on the sleeve of another person. The idea behind the TaSST is to enable two people to communicate different types of touch at a distance. We will outline the design process of the TaSST, describe some initial results from a user study, and discuss possible applications of the TaSST.
Author Keywords
Mediated social touch, haptic feedback, vibrotactile stimulation.
ACM Classification Keywords
H.5.2 [Information interfaces and presentation (e.g., HCI)]: User Interfaces - Haptic I/O, Prototyping.
Introduction
In computer-mediated communication we mainly rely on our visual and auditory senses, for instance in the case of video chat, messaging, or e-mail. However, in real-life communication, we use many more of our sensory capabilities when we communicate with others. One of our senses that, in social interactions, can have profound
effects but has been understudied in mediated
communication, is our sense of touch. Here we present the design of a wearable device that allows a user to touch someone at a distance, by touching their own forearm.
Figure 1: The force-sensitive resistor grid. Without (top) and with (bottom) the foam sheet.
We will first outline related work on mediated social touch. We will then present the concept of the Tactile Sleeve for Social Touch (TaSST), followed by a
description of the first stages of the design process. Next, we will present an initial analysis of the results from the first user study with the TaSST. Finally, we will outline possible applications and scenarios for the TaSST to be used as a tool for research into mediated social touch.
Mediated social touch
Mediated social touch refers to people touching each other at a distance by means of haptic feedback
technology [9]. Through the design of such technologies, different types of touch can be communicated with different purposes. Some approaches are more explorative in nature, and try to communicate a sense of shared presence, for instance through a shared object [3,6,24].
Others seek to mimic, as closely as possible, specific types of touch, such as stroking [23], hugging [18], or kissing [22]. Finally, some approaches use simple actuators, such as vibration motors, to simulate a sense of touch [2], for example as an augmentation of other communication channels [4,20]. However, most existing devices offer limited expressive freedom to users. They may offer only a single form of touch, or only vary the location or intensity of a touch, for instance. Nonetheless, this expressive freedom is important because different types of touch can have different effects in social situations. For example, when a waitress briefly touches a customer on the arm, this customer is more likely to give a tip [7]. However, if the waitress had stroked the customer’s arm repeatedly
instead, the reaction of the customer would probably have been quite different. Another area where different types of touch are relevant, is in the communication of discrete emotions through touch. Studies show that people use emotion specific touch behaviors to distinguish between different emotions [13]. In the next section we will present the design of a device that allows users to communicate different types of touch at a distance.
The TaSST
Concept
In an attempt to enhance expressive freedom for touch over a distance, we designed the TaSST: the Tactile Sleeve for Social Touch. The basic idea was that by coupling a grid of pressure sensors to a grid of vibration motors worn on the arm, users could communicate different types of touch over a distance by varying the location, duration, and intensity of vibrations. When two individuals both wear a TaSST sleeve, different types of touch can be communicated over a distance. This idea was based on research that shows that vibrotactile stimulation can serve as a simulation of real touch in social settings [8, 10]. In the next section we will outline the design process of the TaSST.
Design process
The basic premise of the TaSST was first explored in the context of communicating emotions over a distance. The experiments by Hertenstein et al. [13], where participants communicated discrete emotions by touching the forearm of another participant, served as a major source of inspiration. A simple force-sensitive resistor (FSR) grid was built (Figure 1). In an informal pilot study,
participants expressed a number of different emotions by touching a foam sheet covering the FSRs [14]. In regard to the FSR grid, participants remarked that, due to the
thickness of the foam covering the FSRs, considerable force was required for a touch to be registered. In addition, participants mentioned that the input surface was relatively small, and not representative of a human arm, making the expressions feel more artificial.
Figure 2: Prototypes of the force-sensitive input layer. The one Euro coin in the top image is for size comparison.
Figure 3: First prototypes of the vibration motor output layer.
The comments made by participants during the informal pilot study, made it clear that significant improvements would have to be made to the sensor grid in order for it to be useful for mediated social touch. As the grid of vibration motors would have to be worn on the arm in order to be able to communicate touches through the FSR sensor grid (Figure 1), we decided to make the entire device wearable, by placing the input layer on top of the output layer. The forearm was chosen as a body location, because it is an appropriate location for social touch to occur [8,12,13], and is relatively sensitive to vibrotactile stimulation [19]. The placement of a sensor layer on top of the actuation layer had another benefit, namely that by touching their own arm, users would get direct feedback on the touch they were sending to the other person.
Downsides of using standard FSRs for the input layer were that they require a solid surface to function properly and become less sensitive once covered with a soft material (which was considered important for touches made to the input layer to feel more realistic). Since the device was envisioned to be wearable, the use of rigid materials was considered undesirable. Following this rationale, we designed conductive wool (Bekeart Bekinox w12/18) based FSR compartments, placed in a grid of 4 by 3 compartments that formed the input layer of the first version of the TaSST (Figure 2). We filled 40mm by 40mm fabric (Lycra) pads with approximately the same amount of raw conductive wool. The size of the pads allowed for enough raw conductive wool so that we would
obtain a good level of sensitivity. Copper tape was used to make contact with the wool. Pressing the wool-filled compartments changes the resistance of the wool, and by measuring these changes for each compartment, the input layer serves as a force sensitive sensor surface.
The design of the vibrotactile output layer (Figure 3) was based on studies into vibrotactile displays worn on the forearm [5, 19, 21]. We used pancake-style eccentric mass vibration motors (KOTL KB37B3), placed in a grid of 4 by 3 motors. Vibration motors were used because they are small, cheap, and easy to control using a micro-controller (in our case an Arduino Mega). Moreover, the
independent control of frequency and amplitude that is offered by surface transducers, would not have been useful here, since changes in the frequency and amplitude of vibrotactile stimuli are difficult to perceive [5,16,19].
The duration of, and spacing between the motors,
however, has a more profound impact on the perception of vibrotactile stimuli [5, 19]. We placed each individual motor on a fabric (felt) sheet with a spacing of 40mm between each motor. This spacing was chosen because it matched the size of the sensor compartments
Furthermore, the spacing should allow for relatively accurate single-point identification (i.e. location of a single motor activation) [5,19].
Prior to using the TaSST, a calibration procedure is required to control the intensity of vibration of the motors in the output layer. The input layer is calibrated by first fully compressing it, and then leaving the wool to settle for approximately 10 seconds. This process is used to determine the lower and higher thresholds. Data from the compartments is then smoothed using a low-pass filter and sampled with a 10ms sampling rate.
Figure 4: The TaSST with the input layer attached to the top of the output layer with Velcro. The output layer is strapped to the user’s arm using Velcro straps.
The vibration motors are controlled using PWM (pulse width modulation). Similar to Oakley et al. [19] we defined 7 PWM levels resulting in 7 perceptually different vibration levels of the motors. For calculating the PWM values the system uses the conductivity range of the wool between fully compressed (lower threshold) and idle values (higher threshold), dividing this into seven PWM levels.
TaSST prototype
The first version of the TaSST is depicted inFigure 4.
The output layer containing the 12 vibration motors is covered with a Lycra sleeve and strapped to the forearm using Velcro straps. The input layer consists of 12 sensor compartments, and has a velcro bottom that attaches to the top of the output layer. Two people can both wear a TaSST to communicate a touch over a distance. When one person touches a sensor compartment on the input layer, the other person feels this touch as a vibration in
the same location, and with an intensity that matches the force applied to the sensor compartment by the first person. By touching different sensor compartments for a certain duration, and with a certain amount of force, specific touches can be simulated as vibrotactile patterns.
To test this assumption a user study was conducted. In the next section we will present some initial results from this user study.
Assessing perception of different types of touch with the TaSST
A user study was carried out to assess to what extent the TaSST would be suitable for communicating different types of touch. Morrison et al. [17] define three types of touch, namely: simple, protracted, and dynamic touch.
For each of the three categories we recorded two types of touch using the TaSST, namely: poke, hit (simple); press, squeeze (protracted); rub, stroke (dynamic). We recorded four variantions of each touch type, that varied in location and orientation (e.g. across or along the arm), for a total of 24 touches. These variations were played back to a participant through the output layer of the TaSST. The participants’ task was to imitate the touch they received, as closely as possible, on the input layer of the TaSST.
Participants
In total, 10 people (8 male, 2 female) participated in the experiment. Their mean age was 28.3 (SD = 2.9).
Procedures
Participants were given an explanation of the experiment, and the TaSST. They were led to believe that another person would apply a number of touches to an identical sleeve, and that they would feel these touches as vibrations on their arm. Participants were instructed to think about how the other person touched his/her sleeve,
and to imitate the touch they thought they received as closely as possible on their own sleeve. In actuality, participants received, in random order, the 24 pre-recorded touches. The entire experiment was video recorded.
Results
The video recordings were used by two annotators to code each touch made by participants. We adapted the coding scheme from Hertenstein et al. [13], to represent touches that could actually be made with the TaSST. The coding scheme included the items: rubbing, poking, stroking, massaging, pressing, squeezing, scratching, hitting, tapping, trembling, and pinching.
Coded
Simple Protracted Dynamic total
Simple 44 25 11 80
Prerecorded Protracted 22 38 20 80
Dynamic 29 24 26 79
Total 95 87 57 239
Table 1: Crosstabulation of the categories of prerecorded touches and touches coded from the videos. Note that one dynamic touch was not coded due to a hardware malfunction.
Substantial inter-rater reliability was obtained with Kappa
= .78, p = <.001, 95% CI (.716, .836). The raters discussed the initial coding session in order to reach consensus on all touches that were coded. In a second discussion round, all the touches were recoded into three categories (i.e. simple, protracted, and dynamic). From these data, a cross tabulation for prerecorded (stimulus) and coded (response) touches, was made (Table 1). The table shows that when participants received a simple touch through the output layer, they mostly imitated this touch as a simple touch as well. A similar trend was
observed for protracted touches. However,Table 1 shows considerably more confusion when participants received dynamic touches. Here the imitated touches were spread relatively evenly over all three touch categories.
Conclusions
The initial results from the user study suggest that the first version of the TaSST is most suitable for the communication of simple and protracted touches.
Conversely, it seems the TaSST, at this point, does not accommodate the communication of dynamic touches very well. An explanation for this is that, due to the 40mm spacing between the vibration motors, strokes felt more like consecutive ’pokes’, instead of a smooth motion over the skin. This issue will have to be addressed in the next iteration of the TaSST, for instance by reducing the spacing between the motors. Another option would be to use algorithms that generate tactile apparent movement, by varying the intensity of two or more vibration motors, depending on the direction of the movement [15]. In the next section we will focus on a number of potential applications of the TaSST concept.
Applications and Scenarios
In this section we present a number of possible applications and scenarios for the TaSST. The TaSST concept was born from the idea of having two people communicate different types of touch over a distance.
Furthermore, the TaSST was envisioned to be used as a research tool to study the effects of mediated social touch in different social settings. Therefore we will focus on a number of different research directions instead of practical applications of the TaSST. Though the TaSST was custom-built, we think the design is generic enough (i.e.
using FSRs to control vibration motors), for it to be useful for the study of mediated social touch in general.
Communication of Emotions
Figure 5: Two examples of participants expressing the emotions of anger (top) and love (bottom) by touching the FSR sensor grid [14].
As was previously stated, the design of the TaSST was inspired by experiments of Hertenstein et al. [13] in which one participant communicated discrete emotions by touching the forearm of another participant. Similar to the informal pilot study described in Huisman [14] (see Figure 5), we want to use the TaSST to investigate the way people express emotions through mediated touch. We want participants to express a number of discrete
emotions by touching the input layer of the TaSST. These touches can be recorded and analyzed to identify patterns in the expression of emotions through mediated touch.
Bailenson et al. [1] conducted such a study using a force-feedback joystick to simulate a handshake. We hope to supplement these experiments on the communication of emotions by using the different input method and actuators of the TaSST. These studies should provide insights into the use of the tactile sense for emotional expression over a distance.
Mediated Communication
As a more ecologically valid way to study mediated touch, the TaSST could be used in a general mediated
communication setting, such as during a video call (e.g.
Skype). Here participants could be given the task to explore different ways to use the TaSST during a video call. Such an experiment would be more explorative in nature, and aimed at identifying possible uses of the TaSST. However, specific manipulations could be introduced to study effects of mediated touch. First, the relation between participants could serve as a
manipulation. It is conceivable that, for example, romantic couples would use the TaSST differently than strangers would. Moreover, strangers of the same gender might use the TaSST differently from strangers of opposite gender. Second, the modalities used during the
mediated communication could be manipulated. Here the goal would be to investigate differences in the use of the TaSST in absence of the visual or auditory modalities.
Finally, the task given to participants could serve as a manipulation. While a regular conversation could serve as an interesting scenario, giving participants, for example, a negotiation task, might influence the way they would use the TaSST. Similarly, the use of the TaSST might be different again if participants were asked to engage in a collaborative task.
Turing Test
Another interesting application of the TaSST would be to use it in a Turing test-like scenario. This scenario would be similar to the one described in the previous section, where two participants have a mediated conversation.
However, instead of having a direct connection between the two sleeves of the participants, a computer system could apply specific touches during the conversation or task. In a task orientated study, such touches could be applied at specific moments during the task (e.g.
submitting a new proposal during a negotiation task) to investigate the effect of mediated touch on the specific task outcomes. Moreover, tactile responses made by participants in response to receiving a certain touch, could be investigated by recording the touches made to the input layer. Such studies might provide insights into the role of the tactile modality in supporting the feeling of presence of another person at a distance [11].
Discussion
In this paper we described the initial design of the TaSST, the Tactile Sleeve for Social Touch. The TaSST was designed with the idea in mind that different types of touch are important for mediated social touch in different social settings. To this end we designed a sleeve that is
worn on the forearm, and consists of an output layer containing 12 vibration motors, and an input layer that consists of 12 conductive wool sensor compartments. By touching one’s own forearm, a touch is sent over a distance to someone else’s TaSST, and this person feels the touch as a vibrotactile pattern in the same location, and with the same vibration intensity on their own TaSST. A first analysis of the results from the user study revealed that the TaSST is more suitable for the
communication of simple and protracted touches, than for the communication of dynamic touches. A more detailed analysis of the results from the user study is currently underway. Based on this more detailed analysis, we will make changes to the original design of the TaSST, in order to improve its use for the communication of
dynamic touches. Furthermore, we will use this redesigned version of the TaSST in an experiment to study the expression of emotions, as was outlined in the section on possible applications and scenarios. Following this study, we hope to apply the TaSST in experimental settings that are more ecologically valid. Such studies will focus on the effects that mediated social touch can have, rather than on the use of the TaSST. However, the TaSST is designed according to an iterative design process, so future changes to the TaSST’s design are to be expected. This way we hope to offer a platform that allows for more tactile expressiveness in the study of mediated social touch.
Acknowledgements
This publication was supported by the Dutch national program COMMIT.
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