Evolution, memory processes, and the survival processing benefit to memory : an examination of the unpredictability hypothesis

Abstract

Nairne, Thompson, and Pandeirada (2007) found an advantage in recall for items that were earlier rated for their survival utility in a hypothetical grasslands scenario. This pattern has repeatedly been shown, typically when comparing survival utility ratings given using a grassland scenario to those given using a modern city scenario. This advantage has been attributed to a grassland setting being similar to the critical ancestral environment of early humans. However, recent work has found this effect in situations entirely unrelated to ancestral environments (e.g., outer space), suggesting that the grasslands scenario is not critical to the effect. Moreover, recent anthropological evidence suggests that early humans lived in a time of high climate variability that, in turn, led to a chronically unpredictable environment during the time period most critical to the evolution of modern humans. Thus, rather than having adapted to one specific environment (i.e., grasslands), early humans may have adapted to environmental unpredictability itself. The proposed series of experiments will investigate the hypothesis that uncertainty may be a modifying factor in the survival processing advantage in memory. In the first experiment, participants were given either a randomized or a blocked series of four rating tasks followed by a subsequent test of recall. The second experiment explored the effect of a task relevant background image that also functioned as a means of isolating trials (90% vs 10%) on recall. The third experiment examined the effect of changing biome images (45% vs 45% vs 10%) on recall.