Rapidly acquired shape and face aftereffects are retinotopic and local in origin

Visual adaptation results in aftereffects that exaggerate the difference between successively experienced stimuli. In the tilt aftereffect (TAE), for example, the perceived orientation of a test line is repelled from the orientation of an adapting line. This principle also applies to more complex stimuli. Adaptation to faces can displace the next face viewed along axes such as identity, gender, ethnicity and specific emotions (Webster et al., 2004). The TAE field has been proposed as a general mechanism by which perceptual differences between shapes, including faces, could be enhanced through the systematic application of local TAEs (Dickinson, Almeida, et al., 2010). In this way perception of faces could be systematically modified along any dimension of interest defined by face morphology. Because the time course of adaptation for the TAE is rapid (Sekuler & Littlejohn, 1974) the same needs to be true for shapes and faces and Experiment 1 of this study shows that it is. Moreover, the orientation selective cells in early visual cortex are retinotopically arranged with limited receptive field sizes and so are sensitive to stimuli in particular regions of the visual field. A TAE field explanation for shape and face adaptation requires, therefore, that the shape and face aftereffects are retinotopic and Experiment 2 obtains this result. Experiment 3 exploits the folded face illusion to demonstrate that adaptation to a simple orientation field can also result in a shift in the perceived emotion in a face.