Survival of the fittest... memories

Even though most of us aren't concerned with physical survival on a day-to-day basis, the concept of "survival" remains a potent one -- just think of the persistent success of TV shows like Survivor and Lost. Perhaps this popularity has to do with more than just good advertising and an interesting plot twist. Perhaps it also has to do with the fundamental nature of survival itself.

Darwin's mechanism for evolution -- natural selection -- has often been reduced to the catch-phrase "survival of the fittest." There's more to it than that, of course, but if survival is such an important aspect of evolution, then wouldn't it make sense that traits -- even TV show preferences -- that have to do with survival are more likely to be passed on to successive generations?

A team led by James Nairne used similar lines of thinking as the basis for an investigation of the nature of a different trait: memory. They reasoned that if the brain evolved for survival, then we might be more likely to remember words related to survival then other words. Three groups of volunteers were shown the same thirty words and asked to rate them on one of three different scales. The first group was told to imagine they needed to survive in the wild grasslands of a foreign country, and rate each word for how important it was to their survival. The second group imagined moving to a foreign country and buying a house there, and rated each word on its importance for the move. The final group just rated the words for pleasantness.

The ratings were actually just a means of keeping the readers focused on the words in a particular context -- either survival-related or not survival-related. The key came at the end of the rating session. Now volunteers were surprised with a memory task: they had to write down as many of the words they could remember from the rating session. Here are the results:

Remember, each group rated the same set of innocuous words like broccoli, eagle, screwdriver, and carbon. Yet those who were imagining themselves in a survival situation remembered significantly more of the words than those who were not. Further experiments replicated these results. In one experiment, the same participants rated both "survival" and "moving" words, with the same result. In another, readers were tested on their memory in multiple-choice format, and again words were remembered better in the survival context.

A final experiment required individuals to rate words either for their utility in a survival situation, or how well they elicited a personal memory. This self-referential memory has been found to be reliably more accurate than other memories in previous studies. Once again, the survival context led to better memory:

So even compared with one of the best memory-enhancing devices -- self-reference -- the survival context led to more correct responses. Across the four experiments in the study, 78 percent of those studied showed better survival memories than other memories.

One reviewer suggested that the reason survival memories were better was due to the popularity of shows like Survivor and Lost. So the researchers repeated the study, this time asking participants if they regularly watched either show. Less than 10 percent did, and there was no difference in the study results even when considering the participants who never watched the shows.

Nairne et al. are careful not to make the claim that "survival" is the only factor in whether an item is remembered, but they do make a compelling argument that the nature of the way we recall things is very likely related to evolutionary mechanisms.

Nairne, J.S., Thompson, S.R., & Pandeirada, J.N.S. (2007). Adaptive memory: Survival processing enhances retention. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33(2), 263-273.