COLUMBUS, Ohio - Believe it or not, a 5-year-old could beat most adults on a recognition memory test, at least under specific conditions, according to a new study.
These findings run counter to what has been known for years from memory research - namely, that memory develops from early childhood to young adulthood, with young adults having much better memory than children.
In one study, children were accurate 31 percent of the time in identifying pictures of animals they had seen earlier, while adults were accurate only 7 percent of the time.
And the memory difference was not because adults already have their mind filled with appointments, to-do lists and other various grown-up issues.
The memory accuracy of adults is hurt by the fact that they know more than children and tend to apply this knowledge when learning new information, the findings showed.
"It's one case where knowledge can actually decrease memory accuracy," said Vladimir Sloutsky, co-author of the study and professor and director of the Center for Cognitive Science at Ohio State University.
Sloutsky, who is also associate dean for research at the university's College of Human Ecology, co-authored the study with Anna Fisher, a graduate student at Ohio State. Their research will appear in the August 2004 edition of the journal Psychological Science.
The issue is how people perform a type of reasoning called induction, in which a person uses particular facts to reach general principles. One way of doing induction is by category. For example, if a person learns that a particular cat has a large brain, he can induce that other animals in the same category - in this case "cats" - also have large brains. This is the way most adults perform induction.
But you can also do induction in other ways, such as by similarity. Using the same example, a person could induce that any animal that looks similar to the cat with a large brain, also must have a large brain. In this research, the findings showed that this is how children most often perform induction.
In one study, the researchers showed 77 young children (average age of 5 years) and 71 college students 30 pictures of cats, bears and birds. In some cases, the subjects were first shown a picture of a cat and informed that it had "beta cells inside its body." They were then presented with the 30 pictures of animals, one at a time, and were asked whether each of the animals also had beta cells.
After this phase of the study was done, the participants were shown 28 pictures and asked whether each was "old" - exactly the same picture shown previously - or new. None of the participants knew they were going to be tested about their memory of the pictures.
This is where the children were four times better than adults -- a 31 percent accuracy rate compared to only 7 percent for grown-ups. The reason, Sloutsky said, was because children used similarity-based induction when they were examining the pictures the first time. When they were asked whether each pictured animal had "beta cells" like the first cat they were shown, they looked carefully to see if the animal looked similar to the original cat.
On the other hand, the adults used category-based induction: once they determined whether the animal pictured was a cat or not, they paid no more attention to the details of the picture. So when they were tested later, the adults didn't know the pictures as well as the children.
"When people use category information, they will filter out unrelated information," Sloutsky said. "The adults didn't care about a specific cat - all they wanted to know was whether the animal was a cat or not.
"The children, though, were comparing similarity - whether the animals looked like that first cat who had the beta cells. So they remembered specific items about each picture that helped them remember it later."
The study also included a comparison group in which participants were simply shown the pictures of the 30 animals and told to remember them for a recognition test. In this case - which didn't involve inductive reasoning - adults were accurate 42 percent of the time, compared to only 27 percent for the children.
In a second experiment, the researchers taught 5-year-old children to use category-based induction just like adults do. When they did that, the memory accuracy of the children dropped to the level of adults. This provides additional evidence that it was the type of inductive reasoning the participants used that determined their accuracy, Sloutsky said. It also provides strong evidence that children usually use similarity-based induction, rather than category-based.
While some researchers have believed that children used similarity-based induction, others argue for what is called the "naïve theory," which states that children use category-based induction, just like adults.
"Our study supports the similarity-based approach in children and presents evidence that would be very difficult to account for under the naïve theory," Sloutsky said. "If children used category-based induction, they should not have had higher memory accuracy than adults."
The research was supported by a grant from the National Science Foundation.
Written by Jeff Grabmeier