Poster F118, Tuesday, March 27, 8:00-10:00 am, Exhibit Hall C
The relation between affective touch and pupil size
Chris Dijkerman1, Roel van Hooijdonk1, Sebastiaan Mathot2, Evelien Schat1, Hannah Spencer1, Stefan van der Stigchel1; 1Utrecht University, The Netherlands, 2University of Groningen, the Netherlands
Interpersonal touch is known to influence human communication and emotion. Affective touch is defined as soft stroke on hairy skin with a velocity of 1-10cms-1. This type of touch activates low-threshold unmyelinated mechanoreceptors, known as C-tactile afferents, which have been proposed to play a unique role in hedonic valence and emotion of touch. For other sensory modalities, hedonic processing has been associated with pupil dilation. However, it is unclear whether pupil dilation can be modulated by hedonic touch. The current study investigated how pupil size reacts to both affective and non-affective stroking. Pupil size data was obtained to investigate differences between stroking conditions. Additionally, an adjusted version of the Touch Perception Task (TPT) was used to assess subjective touch pleasantness ratings. Affective (3cms-1) and non-affective stroking (0.3 and 30cms-1) stroking was applied to the dorsal side of the right hand. Results revealed that stroking velocity had a significant effect on TPT-item scores, showing higher positive and lower negative ratings for the affective touch compared to non-affective touch, thereby replicating previous studies. Results, however, revealed no specific pupil dilation for the 3cms-1 condition, instead a logarithmic relation was found between pupil size dilation and stroking velocity. Theze results suggest that pupil size dilation is related to stimulus intensity (e.g. stroking velocity) rather than specific c-tactile stimulation.
Topic Area: PERCEPTION & ACTION: Multisensory