The ability to perceive and distinguish faces is a fundamental role of the visual
system, though how the visual system accomplishes this goal remains poorly understood.
A common method used to explore the neural mechanisms underlying face perception is
to examine face adaptation aftereffects. For instance, when an observer views a distorted
face (e.g. contracted) for a prolonged period of time, a normal face will appear to be
distorted in the opposite direction (e.g. expanded). Several studies have utilized these
adaptation aftereffects in order to investigate how adaptation transfers across different
types of faces, to test whether common or separate neural pathways code different facial
attributes. Two attributes that are thought to be processed by largely separate neural
subsystems are the expression and identity of the face. In the present study, we examined
the selectivity of face aftereffects for differences in gender or expression, in order to
further elucidate how expression and identity are encoded in the brain. We tested the
prediction that adaptation should show stronger transfer across changes in facial
expression because expression changes do not alter the perceived identity of faces. The
results of this study showed weak selectivity for changes in expression or gender, as well
as modest differences between these two forms of natural facial variation. The results
thus were inconsistent with the proposal that variant features of the face, like an
expression change, will have less influence on adaptation than an invariant change, like
gender or identity. Instead, the results suggest that changes in expression or gender have
comparable effects, and may be represented in similar ways at least with regard to the
mechanisms mediating face adaptation
