Affective Touch is encoded by pupil dilation as a comprehensive social
phenomenon
Abstract
Affective Touch plays a pivotal role in regulating emotions, fostering
social bonds, and nurturing affiliations with others. Its emotional and
arousing dimensions rely on specific features of tactile stimulations
characterizing gentle human caresses, such as touch velocity and the
nature of the stroking source. While previous research has examined the
physiological responses to these individual features of Affective Touch,
no study has explored how they interact to shape autonomic activity. In
this study, we investigated whether and how both the nature of the
touching effector (Human hand vs. Artificial hand) and touch type
(Dynamic vs. Static) influenced the participants’ pupil dilation and
their subjective experience during tactile stimulation. We observed that
when participants received a dynamic touch, they displayed an increase
in pupil dilation when the touch was promoted by a human compared to an
artificial hand, and that such discrimination was absent for static
touch. Also, dynamic touch promoted by a human hand invoked a
supralinear enhancement of pupil dilation indicating that the
combination of these two features induced a significantly stronger
autonomic activation than the summed effects of each separately.
Moreover, this specific type of touch was perceived as the most pleasant
compared to all other tactile stimulations. Overall, our results suggest
that pupil dilation could map the pleasant experience of human-to-human
tactile interactions, supporting the notion that the autonomic nervous
system encodes the emotional and hedonic aspects associated with
Affective Touch as a complex and holistic social experience, rather than
solely responding to its low-level sensory properties.