Does affective touch influence the virtual reality full body illusion?

The sense of how we experience our physical body as our own represents a fundamental component of human self-awareness. Body ownership can be studied with bodily illusions which are generated by inducing a visuo-tactile conflict where individuals experience illusionary ownership over a fake body or body part, such as a rubber hand. Previous studies showed that different types of touch modulate the strength of experienced ownership over a rubber hand. Specifically, participants experienced more ownership after the rubber hand illusion was induced through affective touch vs non-affective touch. It is, however, unclear whether this effect would also occur for an entire fake body. The aim of this study was, therefore, to investigate whether affective touch modulates the strength of ownership in a virtual reality full body illusion. To elicit this illusion, we used slow (3 cm/s; affective touch) and fast (30 cm/s; non-affective touch) stroking velocities on the participants' abdomen. Both stroking velocities were performed either synchronous or asynchronous (control condition), while participants viewed a virtual body from a first-person-perspective. In our first study, we found that participants experienced more subjective ownership over a virtual body in the affective touch condition, compared to the non-affective touch condition. In our second study, we found higher levels of subjective ownership for synchronous stimulation, compared to asynchronous, for both touch conditions, but failed to replicate the findings from study 1 that show a difference between affective and non-affective touch. We, therefore, cannot conclude unequivocally that affective touch enhances the full-body illusion. Future research is required to study the effects of affective touch on body ownership.

Autistic Traits Related to the Importance of Interpersonal Touch and Appreciation of Observed Touch during COVID-19 Social Distancing.

Studies have confirmed the significance of touch for psychological wellbeing. Social distancing regulations during the COVID-19 pandemic reduced people's ability to engage in interpersonal touch and caused increased an appreciation for observed touch, as well as a longing for touch within the neurotypical population. Yet, while the impact of social distancing and the importance of touch are evident in neurotypical individuals, it remains unclear how these factors manifest in autistic individuals. Previous research has related high levels of autistic traits to reduced levels of perceived pleasantness of touch and a reduced interest in interpersonal touch. Our study aimed to examine the differences in the appreciation of observed touch and longing for touch during social distancing between individuals with low and high levels of autistic traits. We conducted an online survey on autistic traits, the appreciation of observed CT-optimal touch and longing for touch. Consistent with our predictions, our results confirmed that individuals with high levels of autistic traits evaluated videos depicting CT-optimal touch less favorably compared to those with lower scores on autistic traits. Additionally, only the group with low levels of autistic traits exhibited a longing for touch during social distancing, whereas the group with high levels of autistic traits did not. The results provide insights in the appreciation of touch in relation to autistic traits during the unique circumstances of the COVID-19 pandemic.

Visual perception of the arm manipulates the experienced pleasantness of touch.

Touch, such as a caress, can be interpreted as very pleasant. The emotional valence assigned to touch is likely related to certain bottom-up factors, such as optimal activation of C-tactile (CT) afferents. It is however unclear if besides somatosensory input, contextual factors related to the own body also play a role in the perceived pleasantness of touch. To test this, we manipulated visual appearance of the participant's arm (veridical vision, no vision, pixelated moving statistic projected onto the arm (i.e. crawling skin)). We used slow velocity stroking (CT optimal stroking) with a soft brush to induce pleasant touch, and fast velocity stroking as a control condition. After each visual condition we asked participants (N=23) to rate the emotional valence of the stroking they felt. After slow velocity stroking ratings on perceived pleasantness (but not on perceived unpleasantness) were modulated by visual condition, with veridical vision of the arm resulting in higher pleasantness ratings than both no vision and pixelated vision. We conclude that contextual processes affect the perceived pleasantness of touch. These findings shed a new light on the underlying mechanisms of how humans experience pleasant touch and show that pleasant touch not solely dependents on bottom up information.