Arousal and short-term memory: Effects of caffeine and trial spacing on delayed-alternation performance

Two experiments tested the prediction of Kesner’s (1973) parallel memory-stores theory that arousal reduces retention in short-term memory. Using rats as subjects, the effect of caffeine on delayed-alternation performance in a spatial discrimination was investigated. Trial spacing was also manipulated, both alone and in combination with the drug variable. The results showed that, with massed trials, caffeine facilitated alternation at the short delay and inhibited it at the longer delays tested. Using spaced trials, caffeine decreased alternation at all delays. Spaced trials produced overall superior performance as compared with massed trials. This pattern of results is consistent with the view that caffeine reduces short-term retention but, paradoxically, can also increase performance under massed trials by decreasing proactive interference (i.e., retention) from earlier trials.