Memory organization of objects by shape similarity : clustering and interresponse time effects in free emission and free recall

Abstract

According to some perceptual theories of long-term memory and knowledge, object representations are organized according to shape similarity and other perceptual schemes. A prediction derived from the perceptual theories is that participants' free emission and free recall retrieval sequences should show clustering of object nouns by shape category, with shorter interresponse times for shape cluster (e.g., snake, rope) as compared to shape switch (snake, globe) transitions. However, some amodal theories state that such effects should not occur. The free emission and free recall results supported the perceptual theories, with significant shape clustering, a shape cluster speed advantage in interresponse times, and strategies and mnemonics (reported post-task) that included perceptual similarities and relations. A neural explanation, based in part on Hebb's (1949) ideas and on recent neuroscientific evidence, is proposed to account for the results.