Pauli Laitinen

Feel-good touch: finding the most pleasant tactile feedback for a mobile touch screen button

Earlier research has shown the benefits of tactile feedback for touch screen widgets in all metrics: performance, usability and user experience. In our current research the goal was to go deeper in understanding the characteristics of a tactile click for virtual buttons. More specifically we wanted to find a tactile click which is the most pleasant to use with a finger. We used two actuator solutions in a small mobile touch screen: piezo actuators or a standard vibration motor. We conducted three experiments: The first and second experiments aimed to find the most pleasant tactile feedback done with the piezo actuators or a vibration motor, respectively, and the third one combined and compared the results from the first two experiments. The results from the first two experiments showed significant differences for the perceived pleasantness of the tactile clicks, and we used these most pleasant clicks in the comparison experiment in addition to the condition with no tactile feedback. Our findings confirmed results from earlier studies showing that tactile feedback is superior to a nontactile condition when virtual buttons are used with the finger regardless of the technology behind the tactile feedback. Another finding suggests that the users perceived the feedback done with piezo actuators slightly more pleasant than the vibration motor based feedback, although not statistically significantly. These results indicate that it is possible to modify the characteristics of the virtual button tactile clicks towards the most pleasant ones, and on the other hand this knowledge can help designers to create better touch screen virtual buttons and keyboards.

Crossmodal congruence: the look, feel and sound of touchscreen widgets

Our research considers the following question: how can visual, audio and tactile feedback be combined in a congruent manner for use with touchscreen graphical widgets? For example, if a touchscreen display presents different styles of visual buttons, what should each of those buttons feel and sound like? This paper presents the results of an experiment conducted to investigate methods of congruently combining visual and combined audio/tactile feedback by manipulating the different parameters of each modality. The results indicate trends with individual visual parameters such as shape, size and height being combined congruently with audio/tactile parameters such as texture, duration and different actuator technologies. We draw further on the experiment results using individual quality ratings to evaluate the perceived quality of our touchscreen buttons then reveal a correlation between perceived quality and crossmodal congruence. The results of this research will enable mobile touchscreen UI designers to create realistic, congruent buttons by selecting the most appropriate audio and tactile counterparts of visual button styles.

Designing tactile feedback for piezo buttons

The present aim was to study the preference of tactile feedback stimulations given by non-physical (i.e., solid) piezo-actuated buttons. Participants (n=16) ranked 16 different tactile feedback stimuli varied by 4 output delays and 4 vibration durations. The results showed that the mean ranks of the stimuli differed significantly from each other. The timing parameters of delay and duration interacted with each other, for example, so that preference of certain vibration duration fluctuated in response to different output delays. Using a very short time window (i.e., 10-453 ms) combining both delay and duration parameters of the feedback could result either in favorable or significantly less favorable subjective experience. The results suggest that a preferred perception of tactile feedback from non-physical buttons requires careful design and controlling of the timing parameters.

Designing haptic feedback for touch display: experimental study of perceived intensity and integration of haptic and audio

We studied the subjectively perceived intensity of the haptic feedback and the effects of the integration of the audio and haptic feedback. The purpose of the study was to specify design principles for haptic feedback on a piezo actuator enhanced mobile touch display device. The results of the study showed that the best corresponding physical parameter to perceived feedback intensity was the acceleration of the haptic stimulus pulse. It was also noticed that the audio stimuli was biasing the perception of the haptic stimuli intensity. These results clarify the principles behind haptic feedback design and imply that the multisensory integration should be stressed when designing haptic interaction.

Emotional responses to haptic stimuli in laboratory versus travelling by bus contexts

The present aim was to study if emotional ratings of haptic stimuli are affected by different contexts. A touchscreen device was used to produce 8 stimuli in laboratory and travelling by bus conditions. The stimuli were varied by amplitude, burst number and rise time. 10 participants were to rate the stimuli using four emotion related bipolar scales: pleasantness, arousal, approachability, and dominance. The results showed that the stimuli were rated as more pleasant, less arousing, and less dominant in the bus than in the laboratory. The stimuli with three bursts and high amplitudes were rated as significantly more unpleasant, arousing, and dominating than the low amplitude stimuli with one burst. The results suggest that simple haptic stimulation can evoke different emotional responses. The results can be utilized when designing, for example, pleasant or dominating haptic feedback.