Life Science

Legacy of the Stone-Age Mind

Research suggests we remember better when we’re in survival mode

January 29, 2010

Imagine you are stranded in the grasslands of a foreign land, with nothing but the clothes on your back.  In order to survive, you’ll need to find steady supplies of food and water and protect yourself from predators.

You now share the mindset of our savannah-wandering ancestors, and, says one researcher, being in that mindset can improve your memory.

James Nairne, a psychology professor who studies the evolution of memory at Purdue University in West Lafayette, Indiana, has found that people better remember items from a list when they put themselves in the place of prehistoric humans, and imagine how those items might help them survive.

Human memory has evolved, Nairne suggests, so that thinking of something in terms of its fitness-relevance — how it could help us survive and reproduce in our ancestral environment — makes us more likely to remember it.

“Getting people to think about survival works [to improve memory] really well, presumably because that’s why our memory systems developed in the first place,” Nairne says.

Scientists agree that mental traits, like physical ones, are shaped by natural selection. Evolutionary psychologists investigate how the selection pressures our distant ancestors might have faced shaped our cognitive functions.

Most evolutionary psychology research has focused on stimuli rather than processes, what we think about rather than how we think about it.  But Nairne’s work centers on how people remember when their survival is at stake. He looks at how situation influences memory — specifically, a situation our ancestors likely faced during the Pleistocene Era, which ended 10,000 years ago, when most scientists think our modern cognitive traits developed.

Nairne asked one group of participants to put themselves in the footprints of early humans: You are stranded in the grasslands of a foreign land… He then asked them to rate how relevant each word in a list was to their survival.  Some words (“bear,” “tree”) fit with the wilderness survival scenario; others (“truck,” “screwdriver”) didn’t.

Participants in other groups saw the same words, but were asked to think about them in ways that psychologists have previously shown improve memory: thinking about how pleasant the words are, for example, or visualizing them.

Nairne found that considering the fitness-relevance of the words, more than any other scenario, improved participants’ performance on a surprise memory test.

Henry Roediger III, who studies memory at Washington University in St. Louis, Missouri, was impressed by the result.  “[Nairne] picked all the tasks that have been shown to be very good for memory, then showed his particular task was better than the best task that had been studied over the past thirty years,” Roediger says.

Just how fitness-relevance boosts memory is still uncertain. But Daniel Schacter, a memory researcher at Harvard University, says that while the mechanism is a mystery, the effect is real.

“We don’t really know the exact underlying basis,” Schacter says, “but whatever it is, thinking about survival engages the processes that … push memory in a positive direction.”

Roediger wondered if a modern survival scenario would have the same effect, or if, as Nairne hypothesized, fitness-relevance was specific to the savannah. Roediger asked participants to rate the relevance of words in a survival scenario located either in the grasslands or in a modern city, figuring a city scenario would facilitate memory more than a wilderness one, since “familiar things are generally easier to remember than unfamiliar things.”

“I was really surprised when we got the opposite effect,” he recalls — participants remembered more words when they thought about surviving in the grasslands than in an urban environment.

Nairne, too, is testing the limits of the fitness-relevance memory boost. He has found that participants remember things better when they imagine hunting or scavenging for food out of necessity than when they imagine hunting for sport or joining a recreational scavenger hunt. It seems that improved memory in fitness-relevant situations is tied not just to the kinds of tasks required of our distant ancestors, but to how important those tasks were to their survival.

Although there are some promising results, evolutionary psychology is a contentious discipline.  While Nairne’s work steers clear of making often-contested evolutionary claims based on certain stimuli, like an innate fear of spiders, there are still methodological obstacles.

“With psychological traits, there’s no fossil record,” says Lawrence Shapiro, a philosophy professor at the University of Wisconsin, Madison, who writes about evolutionary psychology. Without a definitive record of our ancestral psychology, “it’s difficult to determine whether a psychological trait is really an [evolutionary] adaptation.”

“Evolution of memory is a very tough issue to get at directly,” acknowledges Schacter. But, he adds, “if you don’t try to get at the topic, you’re probably not going to make much progress at all.”

Even if the particular evolutionary pressures that gave rise to fitness-relevance aren’t clear, Nairne hopes that elucidating the origins of memory will help us understand its current function.

“We now know that if you get people to think about how something relates to a survival situation, they will remember it better than [if you use] virtually all known techniques,” he says. “Whether that’s due to survival or something else, that’s an important thing to know.”

About the Author

Valerie Ross

Valerie Ross studied cognitive neuroscience and creative writing at Stanford University. While it was her fascination with understanding and explaining the mind and brain that first got her interested in science writing, Valerie has now written about everything from the neuroscience of memory to drug-resistant bacteria to general relativity. She has interned with Scientific American Mind, Discover, and Popular Mechanics.



Samantha Stein says:

Don’t we take the known for granted? Remembering survival points in a familiar surrounding on the surface seems easier thus we don’t store it with the same urgency as we would survival tactics in the complete unknown.

h_h says:

It is not clear in the article if one of the control techniques used a similar associative technique to the technique under test. A control technique which uses a similar method but is not related to survival is needed. For example, a list of items which participants rate in order of usefulness for the purpose of making a toy house or a similar objective irrelevant to survival.

Scott says:

I would think we would want to test peoples memories under actual survival stress. Like when they are half starved. Or when they are having projectiles lobbed at them. Or after being turned down for sex.
This study was more about the relationship between a particular fantasy and memory. Did they try–imagine you are a ninja?

Caroline says:

Gee Scott I didn’t realise that turning down a man’s offer of sex was experienced as a survival stress for him. This sounds like an interesting area of research. Now I feel responsible for all my ex lovers stress levels (or were you kidding?!).

The rows of Kounov
The yet unknown four properties of static charge, which were verified and proved by many experiments during an empirical research, explain not only the grouping of rocks in the rows of Kounov but also in many other cases. Men made hills were built across the whole world during the megalithic ages. There are about 100.000 of them on the American continent only. The known fact that friction of two different materials produces static charge has not been applied to flows of water (underground quells, streams, rivers, sea currents) yet. Water molecules create static charge due to their friction with rocks. The charge of water current produces three conductive energetic parts (aura, zones, and inter-zones) in the same way as charges of other matter. These penetrate every matter and create a conductive 3-D raster across the whole globe (the first yet unknown property of static charge). If we place a piece of any matter into one of the three energetic parts of a water current (a rock or earth in our case) that has a lower value of charge a spontaneous transfer of energy occurs between both pieces of matter until their energetic potentials have been equalized (the second yet unknown property of static charge).
The charge of the mound of Kounov did not probably have the value required and it was necessary to increase it. It was possible to perform this in two ways. One was adding more rock and the other adding auxiliary charges. The constructors of the mound decided to add auxiliary charges. They probably monitored the adjustment of the chemical composition of the charge of the mound.
The individual stones in the row were separated by such a distance that their auras overlapped each other. This fulfilled the condition for the creation of the common charge (third yet unknown property of static charge), which gained energy from the three dimensional conductive raster until its value was greater than the energetic value of the mound. After that the lower charge of the mound started to gain energy from charges of the row of rocks. The number of rows of rocks was given by the requirement of the constructors for the energetic value of the mound. By adding every additional row its energy increased. During the equalization of the energetic potentials a transfer of chemical properties occurs in between the charges at the same time (fourth yet unknown property of static charge). By combining rocks of different chemical compositions it is possible to correct the chemical properties of their common charge.
Looking at the bottoming on the individual stones in the rows by small stones it can be concluded that the place of the mound was “energetically hungry”. The small stones reduced the area of the surface that was in contact with the subsoil, which reduced the transfer of energy from the charge of the row of stones into the ground. The great area of the rows allowed for gaining energy from a great area of the energetic raster. This is a unique and admirable way of solving the increase of energy of the existing charge.
From our civilization point of view the technical development of ancient cultures is incomprehensible, but only until we realize that we missed something fundamental about static charge in the last century. Menhirs, dolmens, Logan stones, cromlechs and other similar small structures were used for curative purposes. The purpose of great megalithic structures with an energetic regulation like for example Teotihuacan, San Lorenzo, the pyramid of Akapan and many others that were built in a laborious way remains a mystery.
The above stated properties of static charge explain a lot not only in history but also hint that many yet unknown properties of static charge still wait for their uncovering.
Miroslav Provod

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