Overt and covert identification of fragmented objects inferred from performance and electrophysiological measures

The authors investigated visual processing leading to object identification by manipulating the number of fragments and nature of the study. During th e study, participants either named or drew objects in Experiment 1 and drew them all in Experiment 2. During the test, participants made an identifica tion judgment at each of 6 different fragmentation levels for studied and n ew objects. Fewer fragments were needed to identify studied than unstudied objects. Reaction times were faster for studied than unstudied objects both at identification and at the preceding level. Event-related brain potentia ls (ERPs) to unidentified objects were characterized by a late negativity i n contrast to a positivity to identified objects. ERPs to studied but not t o new objects contained a smaller and later version of the identification p ositivity at level just prior to identification, which was not due to diffe rential response confidence. Much covert visual analysis and even object id entification may precede overt identification, depending on the nature of p rior experience.