Spatial associative memory: A possible species difference in rats and pigeons

Previous research has shown that pigeons can remember which of four spatially distinct responses was last reinforced, for at least 72 h. The present study sought to replicate this finding using rats. Rats were tested in an operant chamber containing four spatially distinct levers. In each session one lever was randomly selected to provide reinforcement for 15 min. This reinforced period was preceded by a non-reinforced period that was 30 s long, on average. During the non-reinforced period the amount the rat pressed on the previously reinforced lever was compared to responding on the other three levers, and was taken as a measure of memory. Sessions were separated either by 17 min, 24 or 72 h. Unlike pigeons, rats responded at chance levels following each of these retention intervals. This finding adds to previous research suggesting differences in cognitive processes in rats and pigeons.