Innate number sense peaks at age 30, declines with aging

Humans and many other animals have an innate ability to quickly sense which of two groups contains the largest number of objects, a skill that is thought to be related to other mathematical abilities. A new study that relied on 10,000 volunteers who took a test on the Internet suggests that this ability peaks around age 30, then declines with age, researchers reported Monday. The fact that this ability improves with age in children and adolescents suggests that it may be possible to intervene in school to improve mathematical ability, the team reported in the Proceedings of the National Academy of Science.

The ability to distinguish between two groups based on size is a universal characteristic of humans -- even those in cultures that do not practice explicit mathematics -- as well as many animals. This ability is, interestingly, one of the few that can be measured in children, adults and the elderly, providing a unique way to investigate how the mind transforms from infancy to senescence. A team headed by mathematician Justin Halberda of the Johns Hopkins University in Baltimore decided to examine this ability by posting a test online. In the test, a series of 300 images of blue and yellow dots were flashed for 200 milliseconds each. The subject was then required to identify which color was represented by the most dots. An example of the test is posted here. Participants were also asked to fill out a questionnaire about their age and how well they thought they did in math in school compared with their classmates. More than 10,000 people between the ages of 11 and 85 from around the world participated in the study voluntarily.

The team found that scores on the test improved gradually throughout the school years, peaking around age 30, then declining. Nonetheless, there were large individual differences in scores among people of the same age. Those differences appeared to be modestly linked to school performance: Those with the best innate number sense reported the highest ability in math in school. A subgroup of nearly 500 subjects were also asked to report their math scores on the SAT. Again, a higher innate numbers sense was associated with higher SAT scores.

“The encouragingly protracted course of developmental change in [numbers sense] precision and the large individual differences across the lifespan raise the possibility of interventions to improve number sense across a range of ages,” the authors wrote. They did not, however, suggest what those interventions might be.