Cognitive Daily

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.

Comments

#1 Keely
April 5, 2007

I’ve never commented before, but this is such a crazy coincidence that I just had to speak up. I’m a freshman at Purdue University– and Dr. Nairne is my intro psych professor! Its an honors psych class and we discuss papers on evolutionary psychology about every other week. We covered Dr. Nairne’s paper just a few weeks ago. Some of my classmates have actually participated in other studies related to this one. The paper is very interesting, but I’ll be more interested in the results of other projects stemming from this one. I’m a biology major and evolutionary mechanisms playing a role in the way we think just makes sense to me. I’m glad Dr. Nairne has done this foundational work to prove this general idea, but I’m hungry for more details.
#2 Dave Munger
April 5, 2007

That’s great. I’m especially glad to hear that Dr. Nairne asks you to read original journal articles in intro psych — so many intro classes just follow the textbook.
#3 Hao
April 5, 2007

The data is nice, but correlations of mean survival ratings with number of subjects who remembered that word would be really cool data.
#4 Amy
April 5, 2007

Eh, I’m a bit underwhelmed. The finding is interesting, but I’d guess what’s probably going on is simply arousal: when imagining yourself in a survival situation, you are more aroused (in the technical sense, not the sexual sense — i.e., more emotionally engaged and alert). There’s lots of research suggesting that arousal can improve memory, as well as other aspects of performance.

If it is arousal, in a way these results arise because the brain evolved for survival — but because we tend to get emotionally engaged when we think about survival, NOT because our memories in particular evolved for survival. (Not sure if that was the claim, but the more restricted claim just doesn’t seem that different from what is already known).
#5 Alan Kellogg
April 6, 2007

Any,

And what’s wrong with arousal. If getting a fellow’s attention improves his odds of survival, I say that’s a good thing.

So we know about the bennies of piquing a person’s interest. It’s nice to get confirmation in another area. Not everybody knows what you know.
#6 Dave Munger
April 6, 2007

Actually, Amy’s got a good point. How would we do if we rated the same words for other, arousing qualities? What if we rated each word for its utility in organizing a romantic tryst?

Arguably, however, sex is survival-related too. Indeed, practically everything survival-related is also arousing, so I think what we’ve really got here is a chicken-and-egg problem.
#7 Dave
April 6, 2007

Given that the self-referential encoding is as effective as they claim, it seems strange that the self-referential condition isn’t significantly better than the moving/pleasantness conditions. Actually, the method used in the self-referential condition is slightly different from that used in the experiment producing the first graph, but in the paper there’s another experiment that replicates the results from the first graph using the method of the second, that is, a within-subject method (all subjects alternate between blocks of survival- and autobiographical-based ratings). If you have access to APA journals online, you can read the paper here.
#8 Alan Kellogg
April 7, 2007

#6

Sounds like a thesis candidate to me. What is the best way of arousing a person’s interest in a subject as to maximize retention of information?
#9 Rob
April 8, 2007

I am underwhelmed– in one case, people have to construct a narrative, have to use the words in a connected fashion. In the other two, words are considered in isolation, as near random bits of data. I really don’t see how survival per se enters the question. I bet you would get the same results if the scenario was to build a house, or plan a meal, or travel downtown. But then again, those, like all activities really, are at the end of the day survival related, so one wonders what exactly is being established.