Abstract:

Words processed under a survival scenario have a remarkable advantage over those processed in other deep processing conditions (e.g. pleasantness rating, self-reference, moving scenario, and intentional learning). This robust phenomenon is known as survival-processing advantage effect. Nairne, Thompson and Pandeirada (2007) suggested that our memory systems were naturally adjusted to process and store fitness-relevant information which was beneficial to surviving and reproducing. However, this evolutionary-based explanation has little empirical support. The current study aimed to confirm this assumption directly. According to the assumption that the survival-processing advantage effect is due to the pressure brought by natural selection, we inferred that it should be equally found among individuals of different ages. Meanwhile, considering the fitness-relevance assumption, processing words in other fitness-relevant contexts using the same paradigm as survival processing should also yield better memory. Two experiments were conducted in the current study. In the first experiment, 300 participants were randomly chosen from five age groups (8, 10, 12, 21, and 64 years old). The participants were then assigned to the primitive hunting scenario or the hunting contest scenario. Primitive hunting scenario described a dangerous surrounding which participants imagined to hunt for the survival of their tribe. By contrast, the hunting contest scenario did not involve life safety. In this scenario, participants were instructed to imagine taking a hunting contest. All the participants were also asked to assess to what extent each word was relevant to the activities in the imaginative scenario. The instructions for the free recall appeared unexpectedly after a two-minute distraction task. In the second experiment, 150 undergraduates were randomly recruited and assigned to one of the five rating tasks: survival, mate selection, pregnancy, raising a child, and self-reference. The survival scenario needed participants imagine to survive without basic materials in foreign grasslands. The mate selection, pregnancy, raising a child scenarios were all related to reproduction. By contrast, the self-reference was unrelated to survival or reproduction and a namely fitness-irrelevant task. The procedures of word assessment and free recall were similar to Experiment 1. In both experiments, the accuracy of free recall, the ratings, and the rating latencies were recorded for analysis. The results of Experiment 1 revealed that the proportion of correct recall was higher in the primitive hunting condition than in the hunting contest condition across age groups. That is, we observed a typical survival-processing advantage effect in all groups. More importantly, there was no significant difference in the amount of survival benefit. Additionally, there were no statistical differences in the rating latencies and the ratings between primitive hunting condition and hunting contest condition within age group. The results of Experiment 2 showed that recall performances in the “mate selection” scenario and the “raising a child” scenario were better than that in fitness-irrelevant task, suggesting a reproduction advantage. The pregnancy condition did not show a memory advantage possibly because pregnancy was less important in terms of evolutionary significance, especially for the younger participants who were lack of experiences about pregnancy. Also, the error rate of free recall, the rating latencies and the ratings were similar to the results of the first experiment. There were no differences between conditions. In accordance with the natural selection explanation, the survival advantages occurred in different ages and the magnitude of the effects did not differ among ages. These results suggested that people prioritized the processing of fitness-relevant information independent of development. However, this conclusion needed to be further verified due to a low power of the ANOVA test. The higher accuracy of free recall found in the scenario of mate selection and raising a child suggested that reproduction-processing and survival-processing had memory advantages compared to fitness-irrelevant processing. Our findings provided good evidence for the natural selection explanation.

Key words: survival-processing advantage effect, natural selection theory, age, reproduction-processing