Graham A. Wilson

Some like it hot: thermal feedback for mobile devices

Thermal stimulation is a rich, emotive and salient feedback channel that is well suited to HCI, but one that is yet to be fully investigated. Thermal feedback may be suited to environments that are too loud for audio or too bumpy for vibrotactile feedback. This paper presents two studies into how well users could detect hot and cold stimuli presented to the fingertips, the palm, the dorsal surface of the forearm and the dorsal surface of the upper arm. Evaluations were carried out in static and mobile settings. Results showed that the palm is most sensitive, cold is more perceivable and comfortable than warm and that stronger and faster-changing stimuli are more detectable but less comfortable. Guidelines for the design of thermal feedback are outlined, with attention paid to perceptual and hedonic factors.

Pressure-based menu selection for mobile devices

Despite many successes in desktop applications, little work has looked at the use of pressure input on mobile devices and the different issues associated with mobile interactions e.g. non-visual feedback. This study examined pressure input on a mobile device using a single Force Sensing Resistor (FSR) with linearised output as a means of target selection within a menu, where target menu items varied in size and location along the z-axis. Comparing visual and audio feedback, results showed that, overall, eyes-free pressure interaction reached a mean level of 74% accuracy. With visual feedback mean accuracy reached 85%. Participants could accurately distinguish up to 10 pressure levels when given adequate feedback indicating a high level of control.

The effects of walking, feedback and control method on pressure-based interaction

This paper presents a study looking into the effects of walking and the use of visual and audio feedback on the application of pressure for linear targeting. Positional and Rate-based control methods are compared in order to determine which allows for more stable and accurate selections, both while sitting and mobile. Results suggest that Rate-based control is superior for both mobile (walking) and static (sitting) linear targeting, and that mobility significantly increases errors, selection time and subjective workload. The use of only audio feedback significantly increased errors and task time for Positional control and static Rate-based control, but not mobile Rate-based control. Despite this, the results still suggest that audio control of pressure interaction while walking is highly accurate and usable.

Perception of ultrasonic haptic feedback on the hand: localisation and apparent motion

Ultrasonic haptic feedback is a promising means of providing tactile sensations in mid-air without encumbering the user with an actuator. However, controlled and rigorous HCI research is needed to understand the basic characteristics of perception of this new feedback medium, and so how best to utilise ultrasonic haptics in an interface. This paper describes two experiments conducted into two fundamental aspects of ultrasonic haptic perception: 1) localisation of a static point and 2) the perception of motion. Understanding these would provide insight into 1) the spatial resolution of an ultrasonic interface and 2) what forms of feedback give the most convincing illusion of movement. Results show an average localisation error of 8.5mm, with higher error along the longitudinal axis. Convincing sensations of motion were produced when travelling longer distances, using longer stimulus durations and stimulating multiple points along the trajectory. Guidelines for feedback design are given.

Baby it's cold outside: the influence of ambient temperature and humidity on thermal feedback

Thermal feedback is a new area of research in HCI and, as such, there has been very little investigation of the impact of environmental factors on its use for interaction. To address this shortcoming we conducted an experiment to investigate how ambient temperature and humidity could affect the usability of thermal feedback. If environmental conditions affect perception significantly, then it may not be suitable for mobile interactions. Evaluations were conducted outdoors in varying environmental conditions over a period of 5 months. Results showed that the ambient temperature has a significant impact on peoples ability to detect stimuli and also their perception of these stimuli. Humidity has a negligible effect for most humidity values. Despite this, previous thermal feedback design recommendations still hold in varying temperatures and humidities showing that thermal feedback is a useful tool for mobile interaction.

Hot Under the Collar: Mapping Thermal Feedback to Dimensional Models of Emotion

There are inherent associations between temperature and emotion in language, cognition and subjective experience [22,42]. However, there exists no systematic mapping of thermal feedback to models of emotion that could be used by designers and users to convey a range of emotions in HCI. A common way of classifying emotions and quantifying emotional experience is through ratings along valence and arousal dimensions, originating from Russells circumplex model [32]. Therefore, the research in this paper mapped subjective ratings of a range of thermal stimuli to the circumplex model to understand the range of emotions that might be conveyed through thermal feedback. However, as the suitability of the model varies depending on the type of emotional stimuli [31], we also compared the goodness of fit of ratings between the circumplex and vector [8,31] models of emotion. The results showed that thermal feedback was interpreted as representing a limited range of emotions concentrated in just two quadrants or categories of the circumplex: high valence, low arousal and low valence, high arousal. Warm stimuli were perceived as more pleasant/positive than cool stimuli and altering either the rate or extent of temperature change affected both valence and arousal axes simultaneously. The results showed a significantly better fit to a vector model than to the circumplex.

Feeling it: the roles of stiffness, deformation range and feedback in the control of deformable ui

There has been little discussion on how the materials used to create deformable devices, and the subsequent interactions, might influence user performance and preference. In this paper we evaluated how the stiffness and required deformation extent (bending up and down bimanually) of mobile phone-shaped deformable devices influenced how precisely participants were able to move to and maintain target extents of deformation (bend). Given the inherent haptic feedback available from deforming devices (over rigid devices), we also compared performance with, and without, external visual feedback. User perception and preference regarding the different devices were also elicited. Results show that, while device stiffness did not significantly affect task performance, user comfort and preferences were strongly in favour of softer materials (0.45 N·m/rad) and moderate amounts of deformation. Removing external visual feedback led to less precise user input, but inaccuracy remained low enough to suggest non-visual interaction with deformable devices is feasible.

Augmenting media with thermal stimulation

Thermal interfaces are a new area of research in HCI, with one of their main benefits being the potential to influence emotion. To date, studies investigating thermal feedback for affective interaction have either provided concepts and prototypes, or looked at the affective element of thermal stimuli in isolation. This research is the first to look in-depth at how thermal stimuli can be used to influence the perception of different media. We conducted two studies which looked at the effect of thermal stimuli on subjective emotional responses to media. In the first we presented visual information designed to evoke emotional responses in conjunction with different thermal stimuli. In the second we used different methods to present thermal stimuli in conjunction with music. Our results highlight the possibility of using thermal stimuli to create more affective interactions in a variety of media interaction scenarios.

In the Heat of the Moment: Subjective Interpretations of Thermal Feedback During Interaction

Research has shown that thermal feedback can be an engaging and convincing means of conveying experimenter-predefined meanings, e.g., material properties or message types. However, thermal perception is subjective and its meaning in interaction can be ambiguous. Interface designers may not be sure how users could naïvely interpret thermal feedback during interaction. Little is also known about how users would choose thermal cues to convey their own meanings. The research in this paper tested subjective interpretations of thermal stimuli in three different scenarios: social media activity, a colleagues presence and the extent of use of digital content. Participants were also asked to assign their own thermal stimuli to personal experiences, to help us understand what kinds of stimuli people associate with different meanings. The results showed strong agreement among participants concerning what warmth (presence, activity, quality) and cool mean (absence, poor quality). Guidelines for the design of thermal feedback are presented to help others create effective thermal interfaces.

The effect of clothing on thermal feedback perception

Thermal feedback is a new area of research in HCI. To date, studies investigating thermal feedback for interaction have focused on virtual reality, abstract uses of thermal output or on use in highly controlled lab settings. This paper is one of the first to look at how environmental factors, in our case clothing, might affect user perception of thermal feedback and therefore usability of thermal feedback. We present a study into how well users perceive hot and cold stimuli on the hand, thigh and waist. Evaluations were carried out with cotton and nylon between the thermal stimulators and the skin. Results showed that the presence of clothing requires higher intensity thermal changes for detection but that these changes are more comfortable than direct stimulation on skin.