LEARNING AND MEMORY FOR HIERARCHICAL RELATIONSHIPS IN THE MONKEY - EFFECTS OF AGING

Young and aged rhesus monkeys were tested on 2 versions of a transitiv e inference task measuring learning and memory for hierarchical relati onships. Animals initially acquired 4 object discrimination problems a rranged such that the relationship between the stimuli followed the hi erarchy A > B > C > D > E. The second version of the task was similar but involved a series of 7 objects. Learning and memory for the hierar chical relationships were evaluated during probe trials in which novel pairs of nonadjacent items (e.g., B and D) were presented for a respo nse. Standard task accuracy measures failed to distinguish young and a ged subjects at any point in training. In contrast, response latency e ffects that are indicative of relational information processing in you ng monkeys were entirely absent in aged subjects. The findings highlig ht the value of a relational memory framework for establishing a detai led neuropsychological account of cognitive aging in the monkey.