Research Article Adaptive Memory Fitness Relevance and the Hunter-Gatherer Mind James S. Nairne, 1 Josefa N.S. Pandeirada, 2 Karie J. Gregory, 1 and Joshua E. Van Arsdall 1 1 Purdue University and 2 University of Aveiro ABSTRACT—Recent studies suggest that human memory systems are ‘‘tuned’’ to remember information that is processed in terms of its fitness value. When people are asked to rate the relevance of words to a survival scenario, performance on subsequent surprise memory tests exceeds that obtained after most other known encoding techniques. The present experiments explored this effect using sur- vival scenarios designed to mimic the division of labor thought to characterize early hunter-gatherer societies. It has been suggested that males and females have different cognitive specializations due to the unique survival tasks (hunting and gathering, respectively) they typically per- formed during periods of human evolution; the present experiments tested whether such specializations might be apparent in memory for words rated for relevance to these activities. Males and females were asked to rate the rele- vance of random words to prototypical hunting and gathering scenarios or to matched, non-fitness-relevant control scenarios (gathering food on a scavenger hunt or in a hunting contest). Surprise retention tests revealed superior memory for the words when they were rated for relevance to hunting and gathering scenarios, compared with when they were rated for relevance to the control scenarios, but no sex differences were found in memory performance. Central to the functionalist agenda in human memory research is the assumption that human memory systems are functionally de- signed (e.g., Klein, Cosmides, Tooby, & Chance, 2002; Nairne, 2005; Sherry & Schacter, 1987). Like other biological systems, memory likely evolved to enhance fitness (survival and reproduc- tion). Accordingly, memory systems may be specially ‘‘tuned’’ to retain information that is fitness relevant. Studies supporting this proposal have shown that thinking about the relevance of infor- mation to a survival situation produces excellent long-term reten- tion (Kang, McDermott, & Cohen, 2008; Nairne, Thompson, & Pandeirada, 2007; Weinstein, Bugg, & Roediger, 2008). In fact, a few seconds of survival processing produces better free recall than virtually all other known memory-enhancement techniques (Nairne & Pandeirada, 2008a; Nairne, Pandeirada, & Thompson, 2008). In the prototypical survival experiment, participants are asked to imagine themselves stranded in the grasslands of a foreign land, without any basic survival materials. Participants are told that over the next few months, they will need to find steady supplies of food and water and to protect themselves from predators. Next, randomly selected words are presented, and participants are asked to rate the relevance of each word to the imagined scenario. In a later surprise memory test, participants typically remember the words rated for relevance to this fitness-relevant scenario better than they re- member words rated for relevance to matched encoding scenarios that are not fitness relevant (e.g., moving to a foreign land or spending time at a vacation resort). Such ‘‘survival-based’’ retention is also better than retention after traditional ‘‘deep’’-processing tasks (Craik & Tulving, 1975), such as thinking about the meaning of an item or forming a visual image. As a product of natural selection, human memory evolved be- cause it enhanced fitness in specific environments of evolutionary adaptedness (Bowlby, 1969; Tooby & Cosmides, 1992), that is, the environments that were present during the extended periods of human evolution. The products of evolution are rooted in the past, by definition, and are likely to reflect the environmentally deter- mined selection pressures faced by human ancestors. Evolutionary psychologists (e.g., Symons, 1992) generally believe that the ma- jority of humans’ cognitive ‘‘sculpting’’ occurred during the Pleis- tocene era (from approximately 1.8 million to 10,000 years ago), during which the human species lived largely as foragers. Conse- quently, memory processing should bear the imprint of the selection pressures faced by foragers; memory should be geared toward re- taining information that is relevant to the specific adaptive prob- lems faced in hunting-and-gathering environments. 1 Address correspondence to James S. Nairne, Department of Psy- chological Sciences, Purdue University, 703 Third St., West Lafay- ette, IN 47907-2081, e-mail: nairne@psych.purdue.edu. 1 This reasoning is simplistic in some respects. For example, knowledge about ancestral environments is limited; forager ‘‘problems’’ undoubtedly varied across disparate environments. Even so, it is possible to generate hypotheses based on a hunter-gatherer model and attempt resolution in the empirical domain. PSYCHOLOGICAL SCIENCE 740 Volume 20—Number 6 Copyright r 2009 Association for Psychological Science