Mental Math Linked to Eye Motion, Brain Scans Show

Ker Than
for National Geographic News
May 8, 2009
When you do math in your head, you're using a recycled product.

Structures in the human brain once devoted only to visualizing spaces are now also involved in performing simple mental math, according to a new study.

The find supports theories that the brain "recycled" more primitive neural structures to accommodate the cultural innovations such as reading and mathematics that gave humans an evolutionary edge.

Scientists in France used a computer program to record brain activity when participants were looking left or right.

The team then used the program to predict when participants were mentally adding or subtracting based on their brain activity.

(Related: "Brain Scans 'Read Minds' With Surprising Accuracy.")

When people performed addition, they triggered the same patterns of brain activity that light up when they looked right. When they did subtraction, the left-looking brain patterns activated.

Previous studies have shown that numbers and space perception are closely linked in the brain, and this new research could help explain why, said study leader Andre Knops of the French health organization INSERM in Gif-sur-Yvette.

The research might also lead to better ways of teaching math in schools, Knops added.

"Teachers could emphasize the link between numbers and space by making use of spatial relations between numbers," he suggested—although such approaches would first have to be validated and tested by educators.

Findings published in this week's issue of the journal Science.

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