On the Correlation Between Tactile Stimulation and Pleasantness

Several studies in the affective haptics research field showed the potential of using haptic technology to convey emotions in remote communications. In this context, it is of interest to simplify the haptic feedback without altering the informative content of the stimulus, with a two-fold advantage. On one side, it would allow the development of affective haptic devices whose technological complexity is limited, hence more compatible with wearability and portability requirements. On the other side, having a simplified set of stimuli would decrease the amount of data to be transmitted, thus improving the overall quality of remote haptic interactions. In this work, we investigated the correlation between the parameters regulating a caress-like stimulation and the perceived pleasantness. This was done by means of two experiments, in which we asked subjects to adjust the temperature and the motion velocity of a set of stimuli in order to find the most pleasant combination. Results indicated that subjects preferred different values of temperature and velocity of the stimulus depending on the proposed tactile stimulation. A small difference in the pleasantness ratings was observed between caresses provided with linear movements and those given as discrete sequences of taps. In particular, participants preferred linear movements set at 34.5 \,^{\circ }\mathrm{C} and 3.4 \,\mathrm{c}\mathrm{m}\mathrm{s}^{-1}. As regards caress-like stimuli provided with discrete sequences of taps, the preferred temperature and velocity were 33.2 \,\mathrm{^{\circ }C} and 2.9 \,\mathrm{c}\mathrm{m}\mathrm{s}^{-1}, respectively. The presence of vibration had a little effect on the perceived pleasantness.