Viewpoint dependence in adaptation to facial identity.

We produced morph sequences between identities at a variety of viewpoints, ranging from the three quarter leftward facing view, to the three quarter rightward facing view. We measured the strength of identity adaptation as a function of changing test viewpoint whilst keep the adaptation viewpoint constant, and as a function of adaptation viewpoint whilst keeping test viewpoint constant. Our results show a substantial decrease in adaptation as the angle between adaptation and test viewpoint increases. These findings persisted when we introduced controls for low-level retinotopic adaptation, leading us to conclude that our results show strong evidence for viewpoint dependence in the high-level encoding of facial identity. Our findings support models in which identity is encoded, to a large degree, by viewpoint dependent non-retinotopic neural mechanisms. Functional imaging studies suggest the fusiform gyrus as the most likely location for this mechanism.