Rats acquire a low-response-cost daily time-place task with differential amounts of food.

Gallistel (1990) theorized that when animals encounter a biologically significant event, they automatically form a tripartite code consisting of the time, place, and nature of the event. Recent research examining such time-place learning (TPL) has shown that rats are reluctant to perform TPL tasks and appear to do so only under high-response-cost situations (Thorpe, Bates, & Wilkie, 2003; Widman, Gordon, & Timberlake, 2000). In the present study, we trained rats on a low-response-cost daily TPL task, in which the amount of food varied with the spatiotemporal contingencies. It was found that rats readily learned this task. We hypothesize that, rather than automatically encoding a tripartite code when faced with a biologically important event, rats instead automatically encode bipartite codes consisting of time-event and event-place information.