Rats’ memory for serially presented flavors: Effects of interstimulus interval and generalization decrement

Abstract

In four experiments, the effect of sequential exposure to a series of five novel flavors on the subsequent neophobic response of water-deprived rats to those flavors when they were presented simultaneously was examined. After a list-test interval of 30 min and a list-interstimulus interval of 10 sec, the rats generally consumed more of the first and last flavors presented in the initial sequence. This finding was taken to reflect the existence of primacy and recency effects. Experiment 1 provided evidence that successive contamination can occur between flavors in the initial list, making subsequent recognition of later flavors in the list more difficult. However, this effect was overcome by presentation of water between each flavor during the list exposure. Experiments 2 and 4 showed that primacy was not a necessary result of successive contamination in this procedure, by demonstrating that increasing the interstimulus interval between list items decreased the size of the primacy effect. This result suggests that rats’ memory for serially presented items may be controlled by mechanisms different from those typically implicated in the human verbal memory literature. In Experiment 3, the question of whether the testing procedure adopted here could have introduced sources of artifactually produced serialposition effects was explored, but no such influence was found.