| Four experiments examined the hypotheses that arousing and stressful reactions enhance long term memory for associated experiences, and individual differences may modulate this effect. To induce arousal, research participants engaged in a cold pressor task in which they immersed their nondominant arm in ice water. Cortisol and self report measures of arousal confirmed that experiencing the ice water was more stressful than a comparable experience with warm water. Despite varying the stimuli (words, pictures) and their emotional value (positive, negative, neutral), the time between the learning and stress inductions (0 to 1 minute), and the possibility of post-learning mental rehearsal, each experiment produced a significant reversal of the hypothesized effect. That is, in each experiment, exposure to a stressor interfered with, rather than enhanced, long term memory for associated material. This result is qualified by two additional observations. First, when the ice water failed to elevate arousal, it also led to significantly poorer long term memory. Second, individual differences in gender, extraversion, and in hormonerelevant conditions (menstral cycle and oral contraceptive use) significantly affected the stress-memory relationship. For example, both women introverts in the arousal condition and women extaverts in the control condition showed poor recall, whereas the reverse pattern produced good recall, suggesting an inverted U-shaped relationship between arousal and long term memory. I conclude that the relationship between arousal and long term memory is more bounded than previously believed and varies with individual differences in traits and states relevant to gender, extraversion, reactivity, and homone levels. |
