Effects of right or left face stimulation on self and other perception in enfacement illusion.

Enfacement illusion is a visuo-tactile illusion elicited by being touched on one's own face while observing another face being touched at the same time, resulting in a change in self-face recognition. Left-face stimulation is usually preferred in enfacement studies. We investigated whether left or right face stimulation has any effect on the vividness of the illusion and if any relationship exists between emphatic abilities, personality traits and vividness of the illusion. The enfacement procedure included two stimuli: a cotton swab touching to face and a syringe approaching to face. We assessed subjective feeling of the illusion using a questionnaire and morphed face evaluations between self and other. Additionally, galvanic skin response (GSR) was measured. The results indicated that the syringe elicited higher GSR than that of touching and left face stimulation was much more sensitive in discriminating synchronous and asynchronous conditions. We found a significant relationship between self-to-other morph evaluations and GSR when the left side of the face was stimulated synchronously. However, a significant relationship was found between other-to-self evaluations and GSR when the right side of the face was stimulated asynchronously. We also noted significant correlations between vividness of the illusion and emphatic concern, extraversion and psychoticism traits.