A year adds up to big changes in brain

Third grade a turning point in how kids solve math problems

Neuroscientists have confirmed what any kid knows: Third grade changes everything. Compared to kids just out of second grade, recent third-grade graduates use their brains in an entirely different way when solving math problems, a study in an upcoming NeuroImage finds.   

“I think this is really fascinating,” says cognitive neuroscientist Daniel Ansari of the University of Western Ontario in London, Canada. “Anybody who doesn’t believe that development is important needs to read this paper, because it really shows how dynamically the brain changes as we learn.”

Cognitive neuroscientist Vinod Menon of the Stanford University School of Medicine and his colleagues recruited 90 children, aged 7 to 9, who had just completed either second or third grade.

The youngsters calculated easy (3 + 1 = 4) or more complex (8 + 5 = 13) addition problems while Menon and his team scanned the children’s brains using functional MRI.

Third-graders’ brains behaved very differently than second-graders’, the team found. “It’s not a minor change,” Menon says. “At this point, what’s clear is that the brain and brain function is undergoing major changes.”

Overall, second-graders’ brains tackled the easy and hard problems about the same way. Third-graders’ brains responded very differently to the easy and the hard questions. This may reflect a cognitive strategy shift as third-graders grow more adept at handling the easy problems.

Third-graders showed heightened activity in a brain region important for working memory, which keeps relevant info handy. Earlier studies of older children found that this region, the left dorsolateral prefrontal cortex, was less active with age while doing math, so the new results may reflect an age-specific approach to math that later gives way to something else, the authors suggest.

Connections between the dorsolateral prefrontal region and regions in the back of the brain, some of which are involved in vision, were also stronger in the third-graders as they crunched numbers, the team found.

It’s not yet clear whether the differences were actually caused by math classes. Normal development may cause some of the changes, but training and skill acquisition probably play a role, too, says developmental psychologist Ann Dowker of the University of Oxford in England. “A lot of it will be due to the fact that the children are receiving instruction, practice and exposure to arithmetic.”

Ansari says that researchers need to figure out what these brain changes actually mean. “School changes your brain, but what do we do with that?” he says. “That’s the next big question.” So far, scientists don’t know whether these changes correlate with stronger math performance, particular kinds of math training or how good a child will be at math in the future.  

Studies like this may ultimately help educators figure out the best kinds of math instruction, Ansari says, though the science isn’t strong enough yet. “It’s very risky at the moment to say you can get definite answers from brain imaging about how to teach children math,” he says. Yet one day, brain scans might serve as a means of testing the effectiveness of competing instruction methods, such as rote memory learning and more concept-based approaches.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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