Effect of arousal and retention delay on memory: a meta-analysis.

Two meta-analyses were conducted to examine the magnitude of the interaction between arousal and retention delay on various types of memory, e.g., verbal, visual, etc., as initially reported by Kleinsmith and Kaplan in 1963 and 1964. Results of the first meta-analysis (29 studies, N = 2,637) indicated that the interaction was robust (d = .779), with low arousal leading to better immediate memory than high arousal, whereas high arousal led to better delayed memory than low arousal. Incorporating additional studies, a subsequent meta-analysis (48 studies, N = 3,143) on the effect of arousal on memory, taking retention delay as a moderator, provided further support. At a 2-min. delay, low arousal led to better immediate memory than high arousal (d = -.459). This difference decreased at a 20-min. delay (d = .106), when directions of high and low arousal effects on memory appeared to reverse. At longer delays than 20 min., high arousal led to better delayed memory than low arousal (ds = .753, .219, and .472, for delays of 45-min., 1-day, and more than 1-day, respectively).