Do People Show Enhanced Memory For Survival-relevant Information?

Survival is one of the most important adaptive problems. In face of survival pressure, human memory system might make some adjustment. Recently, Nairne et al., (2007) demonstrated a striking memory phenomenon, namely survival advantage: words rated for relevance to a grasslands survival scenario were remembered better than identical words encoded under other deep processing conditions (relevance to moving a new house, pleasantness judgment, and self-reference). Enhanced memory for survival-relevant information might be a possible strategy for mankind to solve adaptive problems. Based on the findings of survival advantage, the aim of the present study was to examine whether the strategy truly exists. Three experiments were listed below:Experiment 1: By adopting a similar experimental paradigm to Nairne et al., (2007), Weinstein et al., (2008) found that the grasslands survival scenario produced better recall than a city survival scenario. Grassland might be a primary scenario in the human evolutionary history, but city is a rather new scenario to mankind. Therefore, they argued that the result might reflect adaptive bias for survival. However, grasslands might be more dangerous than cities, so their study could not rule out the effect of the feeling of danger which might enhances retention. In order to clarify this controversy, here we introduced a new encoding condition - desert survival scenario, which is more dangerous. The results show that: free recall performance under grassland survival scenario outperformed its counterpart under city survival scenario, but were not better than performance under desert survival scenario. The findings were consistent with Weinstein et al.'s evolutionary account.Experiment 2: By employing a similar experimental paradigm, Nairne et al., (in press) also found that a prototypical hunting (for survival) scenario produced better recall than a hunting contest (for winning a game) scenario. Here we adopted identical instructions and procedures to Nairne et al., (in press), but used pictures and words as study materials and recognition as memory test. However, no significant difference between two encoding conditions was found, and it suggested that survival advantage might be only sensitive to recall rather than recognition.Experiment 3: Both Nairne et al., (2007) and Experiment 1 showed that, participants showed enhanced retention to high-survival value words rather than low-survival words. Nevertheless, this effect might be also explained by the congruity effect, i.e. high ratings in encoding phase corresponds high memory performance (no matter how to rate). To explore these two possible accounts, we asked the participants: (1) to judge the printed color of the studied words (red, green, yellow, green); (2) to make yes/no judgments in recognition task; (3) and finally to rate survival-relevance of studied words to grasslands survival scenario. The ratings of "hit" words were no more than the ratings of "miss" words, which suggested that people do not show enhanced memories for higher survival value words.In conclusion: (1) Comparing to the control conditions, when judging survival values of items in a certain imagined situation (e.g. grasslands survival scenario), people showed enhanced memory for survival-relevant information (in recall but not recognition); (2) When the encoding condition is unrelated to survival problems, participants do not show this adaptive bias.