The inversion effect in infancy: the role of internal and external features.

The present work examined the changing role of inner and outer facial features in the recognition of upright and inverted faces in 5-, 7-, and 9-month-olds. Study 1 established that the "inversion effect" (impaired recognition of an inverted face) was present in infants as young as 5 months. In Study 2, internal and external features were inverted separately. Disrupting the internal configuration by inversion impaired recognition at all ages; disrupting the external configuration impaired recognition only at 5-months. In Study 3, an upright familiar face was paired with one having either novel internal or novel external features. The results confirmed that the 5-month-olds used only the external features to recognize faces, whereas older infants were as adept at using internal features as external ones. These findings suggest a shift, after 5 months, away from dependence on external features for face recognition and toward greater reliance on internal ones.