Multisensory and Gaze-Contingent Stimulation of the Own Face

When observers’ own face is stroked in synchrony, but not in asynchrony with another face, they tend to perceive that face as more similar to their own and report that it belongs to them. This “enfacement effect” appears to be a compelling illusion and also modulates social cognitive processes. This thesis further examined the effect of such synchronous multisensory stimulation on physical and psychological aspects of the self. Chapter 2 explored whether multisensory facial stimulation can reduce racial prejudice. White observers’ faces were stroked with a cotton bud while they watched a black face being stroked in synchrony. This was compared with a no-touch and an asynchronous stroking condition. Across three experiments, observers consistently reported an enfacement illusion after the synchronous condition. However, this effect did not produce concurrent changes in implicit or explicit racial prejudice.

Chapter 3 explored whether a similar enfacement effect can be elicited with a novel gaze-contingent mirror paradigm. In this paradigm, an onscreen face either mimicked observers’ own eye-gaze behaviour (congruent condition), moved its eyes in different directions to observers’ eyes (incongruent condition), or remains unresponsive to the observers’ gaze (neutral condition). Observers experienced a consistent enfacement illusion after the congruent condition across two of three experiments. However, while the mimicry of the onscreen face affected observers’ phenomenological experience, it did not alter their perceptual self-representations.

A final experiment, in Chapter 4, further investigated the cognitive locus of the enfacement effect by using ERPs. Observers were exposed to blocks of synchronous and asynchronous stimulation. ERPs were then recorded while observers were presented with images of (a) a synchronously stimulated face, (b) an asynchronously stimulated face, (c) their own face, (d) one of two unfamiliar filler faces and (e) an unfamiliar target face. Observers consistently reported an enfacement illusion after the synchronous condition. However, this enfacement effect was not evident in ERP components reflecting early perceptual encoding of the face (i.e., N170) or subsequent identity- and affect-related markers, such as the N250 and the P300.

Altogether the results of this thesis show that it is possible to enface a face, even when it belongs to a different ethnic group to that of the observer. This effect is such that observers report that the enfaced face belongs to them. Interestingly, a similar phenomenological enfacement experience can be obtained with gaze-contingent mirror paradigm. However, this enfacement effect seems to be too short-lived to be reflected in ERP components.