Face adaptation : behavioural and electrophysiological studies on the perception of eye gaze and gender
Whereas the investigation of perceptual aftereffects has a very long tradition in studies on low-level vision, the report and analysis of face-related high-level aftereffects is a very recent line of research. Webster et al. (2004, Nature) first showed a visual aftereffect on the perception of face gender by demonstrating that adaptation to male faces biased the subsequent classification of androgynous faces towards female gender. Similar adaptation effects have also been observed for one of the most important social signals: human eye gaze. Jenkins et al. (2006, Psychological Science) found that adaptation to gaze in one direction virtually eliminated participants’ ability to perceive smaller gaze deviations in the same direction. The present thesis further examined these high-level face aftereffects by determining the temporal characteristics of gaze adaptation and by analysing the neural correlates of eye gaze and gender adaptation. A behavioural study on the temporal decay of gaze adaptation effects shed further light on their basic characteristics: not only was the aftereffect surprisingly long-lasting, but its exponential decay revealed remarkable similarity with the time course of low-level adaptation effects. Further, in a series of event-related potential (ERP) studies it was found that the N170 was only marginally affected by both eye gaze and gender adaptation, whereas pronounced effects of both kinds of adaptation emerged in the P3 component with smaller amplitudes in response to test stimuli similar to the adaptation condition. Finally, gaze adaptation was found to affect ERPs in an earlier time interval ~250-350 ms which appeared to be sensitive to the discrimination between direct vs. averted gaze even when this was only an illusionary percept induced by adaptation. Together, these studies extend previous knowledge of the temporal parameters and the neural correlates of high-level face adaptation.