Within-session dynamics of categorical and memory mechanisms in pigeons.

The current experiments used categorical mid-session reversal (MSR) to examine how eight pigeons utilized categorical and item-specific mechanisms to learn and solve a novel variation of this task. Employing a fixed order of trial-unique pictorial items from two categories (flowers and cars) on each simultaneous discrimination trial, categorical and item-specific information was available during each session's 80 trials. Choices to one category were rewarded for the first 40 trials, after which the correct category was reversed (e.g., car correct early → flower correct late). This procedure selectively impacts the time-modulated utility of categorical identification, but leaves exclusively item-specific information intact. Results revealed that categorical control emerged rapidly and before item-specific memorization, which came after extended experience. Both types of control occurred within a session, with control modulated by their time-based relative utility. The implications for the timing, ordering, and attention by animals to categorical and item-specific information is considered.