Scientists Changing Theories About Memory

Memory

Scientists try to unlock keys to memory. iStock.com hide caption

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Everyone knows that frustrating feeling when something is just "on the tip of your tongue." Like when you run into an old acquaintance on the street — you know you know the person's name, but it just seems slightly out of your grasp.

Neuroscientists are now studying that phenomenon with brain scanners, and their research is completely changing their view of how human memory works, explains Jonah Lehrer, editor-at-large at Seed magazine and author of Proust Was a Neuroscientist.

Scientists can watch the brain's activity as subjects struggle to remember slightly obscure words. What they see, says Lehrer, is the activity of the brain's frontal lobes, the brain's search mechanisms. "The brain is saying, 'I know that word is in here somewhere.' You can see the brain searching itself," says Lehrer. "It's this kind of frantic, manic process. The brain is very upset because it can't find what it certainly knows."

Lehrer says that what scientists are seeing is "metacognition" — the process of the brain thinking about how it thinks.

By looking at brain activity during the scans, scientists are concluding that earlier notions of how memory works need to be revised. The old model of memory, says Lehrer, is that the brain was like an immense filing cabinet, where knowledge was stored in a logical order. "Now, thanks to 'tip of the tongue' research," says Lehrer, "they're realizing that it's not like a file cabinet at all but like a very, very messy desk, cluttered with big piles of paper, so when you misplace a word or a name, what you're trying to do is find one piece of paper amid all these billions and billions of piles of paper."

But, as those of us with messy desks know, there are all sorts of sorts of ways finding that one piece of paper in the clutter when we need to. We may know it's near another piece of paper about the same subject. We might know that it was put in a pile at the same time as another piece of paper we see on top.

Scientists are discovering that the brain works in a similar way, and the way people remember "tip of the tongue" is one indication. For example, if someone is having trouble remembering the word "contraband" they'll be much more likely to come up with the word if someone else mentions the word "continue," which has a similar first syllable. The connections can be second-hand as well. Someone trying to remember the word "biopsy" may remember it if shown a photo of a motorcycle — the motorcycle might suggest a "bicycle," whose first syllable would then lead them to the proper answer.

"It's astonishing how rare 'tip of the tongue' moments are considering all the stuff we have crammed into our head," Lehrer says. He says scientists have measured it to occur about once a week on average and adds that, although the frequency increases with age, it's not for the reasons most people assume.

"Most people think that as you lose memories with age, what happens is the memories disappear, they vanish," he explains. But that's not the case — the memories are probably still there, but the frontal lobes of the brain lose their volume with age, making it harder for the brain to search itself. "It's this kind of paradoxical moment — the memories are there, they're in your neurons," says Lehrer, "and yet your brain can't find that name because your frontal lobes have shrunk a little bit."

Wouldn't it be easier for our memories and better for us as a species if our brains stored information in a more orderly way, as in the filing cabinet model? Lehrer points out that our brains are a byproduct of evolution. "Natural selection is a hacker, not an engineer," he says. "We're not always designed in the most logical way possible."

But, as one researcher told him, that lack of logic also has its benefits: "If our brain wasn't so messy, we wouldn't be so creative. Messiness also allows us to find those serendipitous connections that we don't expect to connect."

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