Humans' inborn "number sense" improves during school years, declines during old age and remains linked throughout the entire lifespan to academic mathematics achievement. So says a Johns Hopkins University study that has used the Web to collect data from more than 10,000 people ages 11 to 85. "Number sense" describes human and animals' inborn ability to intuitively size up the number of objects in their everyday environments.

Citizen scientists can take the same test used in this experiment by visiting the Panamath Web site. During the test, participants see a random number of circles on screen for 600 milliseconds (0.6 seconds). Their job is to decide whether there were more yellow circles or more blue circles.

Panamath measures a participant's Approximate Number System (ANS) aptitude. The simple task of deciding whether there are more blue dots or yellow dots in a brief flash says a lot about the accuracy of one's basic gut sense for numbers. Participants can view the results of their test immediately afterward and compare their performance with others in their age group.