List item memory in rats: effects of delay and delay task.

The Serial Position Effect (SPE) was studied in rats using 2 manipulations analogous to those that have been shown to decrease the recency effect but leave the primacy effect intact in human Ss. In Part 1, delays (5 s to 60 s) were imposed between exposure to a sequence of arms presented in a 12-arm radial maze and a subsequent test phase. In Part 2, the effect of free access to food in a short (10-s) delay was examined. The results from Parts 1 and 2 showed that the primacy and recency effects were differentially sensitive to the delay and events within it. In particular the recency effect was found to be more sensitive to disruption from these sources. The present demonstration of a reduction in recency with procedures analogous to those used with humans extends the evidence, suggesting that the SPE obtained in rats and humans is a similar phenomenon.