Repetition priming of possible and impossible objects from ERP and behavioral perspectives

Theorists postulate that two-dimensional objects that can exist in three dimensions (3D, labeled "possible") are represented by a structural description system (SDS). Objects that cannot because of anomalous structural features (labeled "impossible") are not represented by the SDS. To test these assumptions, ERPs and RTs were recorded while subjects classified possible and impossible objects (each presented three times) as left- or right-facing. Repetition of both types of objects led to RT facilitation. ERP repetition priming occurred only for possible objects, which took the form of a long-duration increase in positive amplitude from about 500 ms for second and third relative to first presentations. The data suggest that RT priming of impossible objects depends on part-based structural encoding, whereas ERP priming most likely reflects contact, upon repetition, with a unitized representation that exists only for possible objects.