Contrast-based face adaptation: a new method for exploring the organization of face-space

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Faces are some of the most complex visual stimuli that the human brain processes. An important question in research on object recognition is how the visual system organizes and accesses neural representations of faces. Adaptation is a powerful experimental technique: by examining how responses to different faces are affected by preview of a particular face, we can understand what the system encodes about faces, how these are represented, and how these representations interact. We have developed a new adaptation technique that asks how the amount of contrast needed to perceive a specific face is affected by preview of the same or other faces. Our technique has shown that a short preview facilitates perception of the same face, but inhibits perception of other faces. We can use this effect to ask a series of key questions. Does the degree of inhibition depend upon the similarity of the other face to the adapting face? Is there a distinct segregation of face space by gender? How do representations of the identity of the face and representations of facial expression interact? Is the organization of these representations dependent on face-expert mechanisms that are not available when faces are seen upside-down? Our plan is to test the hypotheses driving these questions and use computational models of neural networks to simulate the findings and to suggest how the neural representations of these complex visual stimuli might be organized and interact. This type of knowledge will advance our understanding of the storage of object information and the mechanisms that contribute to the rapid and effortless recognition performance of the human visual system.