ARI SHAPIRO, HOST:
The human brain knows what it knows. Brain scientists call this awareness of our own thoughts metacognition. It's a concept that Donald Rumsfeld, the former secretary of defense, memorably explained to reporters this way.
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DONALD RUMSFELD: There are known knowns. There are things we know we know. We also know there are known unknowns. That is to say, we know there are some things we do not know.
SHAPIRO: NPR's Jon Hamilton reports that scientists now have a better understanding of where this remarkable ability came from and how it works all thanks to a study of rats.
JON HAMILTON, BYLINE: The human brain spends a lot of time monitoring what we know. And Victoria Templer of Providence College says that's really useful.
VICTORIA TEMPLER: Say you're going over to a friend's house for a party and you ask yourself, do I know how to get there?
HAMILTON: Templer says our brains instantly know whether to say, yes, I remember the way, or, no, better check Google Maps. This awareness of our own memories is a special type of metacognition. It's called metamemory. It sounds like a pretty sophisticated ability, but Templer found evidence that rhesus monkeys could do it. And she wondered whether rats could, too.
TEMPLER: Their brain structures are actually very similar to ours.
HAMILTON: Templer had nine rats learn to recognize several odors.
TEMPLER: Cinnamon, thyme, coffee...
HAMILTON: And paprika. First the rats were exposed to one of these odors in a cup. A bit later, they took a test to see if they could pick out that same odor among several cups. If the rats got it right, they got a Froot Loop. If they got it wrong, they got nothing. The next step was to see whether the rats could use metamemory.
TEMPLER: So they're given the choice - do you want to answer this memory question...
HAMILTON: And try for the whole Froot Loop.
TEMPLER: ...Or do you want to not take that memory test at all and get a less-preferred but guaranteed reward?
HAMILTON: A quarter of a Froot Loop, which would indicate that they knew they didn't know. Templer says this created a dilemma for each rat.
TEMPLER: It would rather have a quarter of a Froot Loop than nothing. But a rat's going to want a whole Froot Loop, right?
HAMILTON: To make the best decision, the rats would have to assess their own memories. And Templer reports in the journal Animal Cognition that they did. When animals knew they remembered an odor, they went for the whole Froot Loop. When they knew they didn't remember an odor, they skipped the test and settled for a quarter of a Froot Loop. What they didn't do much was simply guess and risk no Froot Loop at all. Templer says knowing that rats possess metamemory could have practical applications.
TEMPLER: It can help us hopefully have an animal model to study memory dysfunction in - you know, for early-stage drug trials.
HAMILTON: To find treatments for diseases like Alzheimer's, which often affects a person's metamemory. The finding also suggests an evolutionary path from a primitive ability in rats to humans' highly developed ability to monitor their own thoughts. Michael Beran of Georgia State University studies the cognitive abilities of primates. He says even humans aren't born with metamemory.
MICHAEL BERAN: So you'll ask a child at 3, do you know who the first president was? And they'll say, yes, of course I do. Who is it? I don't know. Whereas by time a child is 5 or 6, you start to see them do things like pause when being asked a question. Well, do you know who the first president was? And you'll see that pause, and then they'll go, no, I don't; who was it?
HAMILTON: Beran says rats and people probably use metamemory in very different ways. He says for a rat, it's about knowing whether you remember that predator in the distance. For people, he says, metamemory is more likely to help us navigate social interactions.
BERAN: I'm notorious for walking across campus and seeing a former student and immediately knowing that I know who she is but also knowing that I don't know her name right now.
HAMILTON: A situation Donald Rumsfeld might call a known unknown. Jon Hamilton, NPR News.
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