What does a crowded bus have to do with your ability to learn math? If you can tell by a quick glance whether more people are in the front or the back, chances are you had an easier time with numbers in school, a new study reveals. Success in mathematics has already been linked to factors such as short-term memory. Many experts also suspected a role for the approximate number system (ANS), a sort of mental sense that allows us to judge the relative quantities of various objects, such as people in the front or back of a bus. But no one had studied the extent to which this ability varies in people, or whether it relates to math proficiency.
Psychologist Justin Halberda of the Johns Hopkins University in Baltimore, Maryland, and his colleagues tested the ANS in 14-year-olds. The 64 children watched a computer screen that flashed split-second images of blue and yellow dots in various ratios. A handful aced the test; they could easily identify the more abundant color in ratios as fine as 9:10. Others had trouble with ratios as low as 2:3. “We were surprised to see this very wide variation,” Halberda says.
The researchers were even more surprised to see how strongly the acuity of the ANS correlated with the students’ test scores, going as far back as kindergarten. The ANS explained a whopping 28% to 32% of the variation of third-grade performance on two national tests, called the TEMA-2 and WJ-RCALC, for example. “This was really astounding,” Halberda says. The relationship held even when they controlled for IQ, spatial reasoning, short-term memory, and 13 other factors, the team reports online this week in Nature. It’s not clear exactly how the ANS might improve skill in formal mathematics; possibly it helps one judge whether an answer to a math problem is even plausible.