Properties of time-place learning by pigeons, Columba livia.

Pigeons received discrimination training in which food reinforcement for key pecking was conditional upon both spatial and temporal cues. In Experiment 1 food was available for periods of 15 min at each of four locations (pecking keys) during a 60-min trial. However, unlike the procedures used in a previous experiment (Wilkie and Willson, 1992, Experiment 2), food availability did not change over time from one location to the next in a simple monotonic (e.g. counterclockwise) manner. Despite making food available in a figure-eight pattern, pigeons' key pecking was still jointly controlled by the spatial and temporal cues. Experiment 2 sought evidence on the nature of the timing mechanism underlying this behavior. The results of manipulations such as turning all of the keys off, and removing and replacing the subjects, suggested that a stopwatch-like mechanism with properties of stop/restart and reset underlies pigeons' time-place learning, at least with the temporal parameters used in these experiments. This finding contrasts with others in the literature that suggests that a circadian mechanism controls birds visits to different spatial locations. It will be important in future research to determine the relations between the different timing systems involved in time-place learning by foragers.