Have I seen you before? Evaluating the learning of naturalistic faces and faces in art

People are highly skilled at recognizing familiar faces due to the development of identity representations that are invariant to viewpoint and low-level features. However, how such view-invariant representations emerge for unfamiliar faces remains debated. This EEG study examined the neurophysiological basis of face learning, and how viewpoint generalization is shaped by experience (i.e., increasing familiarity) and stimulus realism. Adult participants performed an identity-matching task with novel faces varying along a realism continuum, from photographs to less and more abstract artistic styles (Renaissance vs. Cubism). Identity (same vs. different) and viewpoint (repeated vs. changed) were orthogonally manipulated within face pairs. Early face structural encoding (N170; 150-190 ms) was modulated by face realism and by viewpoint-related perceptual demands. The subsequent N250r (220-270 ms) was sensitive to the formation of viewpoint-invariant identity representations in memory, with different temporal dynamics across face types: viewpoint tolerance increased gradually for photographs with repeated exposure, whereas it emerged earlier for stylized faces. After repeated exposure, a reliable N250r was also observed for unseen, novel views, suggesting that learning supports progressively more stable and potentially more abstract identity representations. These findings are discussed in light of stimulus structure and the role of top-down processes in the formation of view-invariant representations.