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 the study, participants either named or drew objects in Experiment 1 and drew them all in Experiment 2. During the test, participants made an identification judgment at each of 6 different fragmentation levels for studied and new 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 potentials (ERPs) to unidentified objects were characterized by a late negativity in contrast to a positivity to identified objects. ERPs to studied but not to new objects contained a smaller and later version of the identification positivity at level just prior to identification, which was not due to differential response confidence. Much covert visual analysis and even object identification may precede overt identification, depending on the nature of prior experience.