Active and passive-touch during interpersonal multisensory stimulation change self–other boundaries

Abstract

In the "enfacement" illusion seeing an unfamiliar face being touched at the same time as one's own face evokes changes in self-face recognition. We investigated the contribution of proprioceptive and motor signals derived from self-generated actions in the sensory-driven malleability of self-other boundaries during the "enfacement" illusion. Changes in self-face recognition during active- and passive-touch interpersonal visuo-tactile stimulation were quantified by means of psychophysical and psychometric tasks. Active- and passive-touch evoked comparable changes in the categorical boundaries of self-other distinction, changing the extent to which the other is assimilated into the mental self-representation. Actively touching or simply feeling touch on one's own face with concurrent observed touch on someone else's face seems to elicit comparable changes in self-recognition, suggesting that afferent input might be sufficient for updating one's body-image, although some components of the experience of self-identification seem to be more affected by passive- than by active-touch.