Computer simulation of pigeons' performance on a spatial memory task.

Delayed matching of key location is a useful paradigm for the study of pigeons' short-term memory for a spatial location. On each trial a randomly selected key from a matrix of keys is lit briefly as a sample and followed by a retention interval. During the ensuing choice period the sample and one of the non-sample keys are lit; choice of the sample is correct and rewarded whereas choice of the distractor key is not. The computer simulation of performance on this task is based on a simple model: We assume that the pigeon has knowledge of the location of the keys stored in a map-like reference memory. We also assume that short-term memory involves an attention focus or "pointer" that "drifts" on the surface of this map. The pointer migrates from a randomly determined position during the intertrial interval towards the location of the sample when this stimulus is presented. It wanders randomly from its previous position when this cue is no longer present in the retention interval. During the test for retention the bird selects the location (i.e., sample or distractor) closer to the location of the pointer on the map of the matrix. The simulation successfully reproduced several of the phenomena observed in delayed matching of location experiments and provided an account of some hitherto perplexing results. As well, the model successfully predicted some new empirical data.