Adaptive memory: nature's criterion and the functionalist agenda.

Memory researchers traditionally ignore function in favor of largely structural analyses. For example, it is well known that forming a visual image improves retention, and various proximate mechanisms have been proposed to account for the advantage (e.g., elaboration of the memory trace), but next to nothing is known about why memory evolved such sensitivities. Why did nature craft a memory system that is sensitive to imagery or the processing of meaning? Functional analyses are critical to progress in memory research for two main reasons: First, as in applied research, functional analyses provide the necessary criteria for measuring progress; second, there are good reasons to believe that modern cognitive processes continue to bear the imprint of ancestral selection pressures (i.e., cognitive systems are functionally designed). We review empirical evidence supporting the idea that memory evolved to enhance reproductive fitness; as a consequence, to maximize retention in basic and applied settings it is useful to develop encoding techniques that are congruent with the natural design of memory systems.