Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

A common carnival game is to ask people to guess the number of jellybeans packed into a jar. The chances that anyone will get the exact number right are low. But what about the chances that someone will guess 17 or 147,000? Probably even less than the chances of guessing the correct answer; 17 and 147,000 just seem irrational. Why? After all, if the beans cannot be taken out and counted one-at-a-time, how can someone tell that an estimate is too high or too low?

It turns out that in addition to verbal counting (something clearly learned), people appear to possess hardwired mental and neural mechanisms for estimating numbers. To put it colloquially, it is what might be called an ability to guesstimate, or “ballpark.” Experimental psychologists call it the “Approximate Number Sense,” and recent research with an experimental paradigm of the same name has begun to uncover the underlying computations and neural mechanisms that support the ability to guesstimate.

This video demonstrates standard procedures for investigating nonverbal numerical estimation with the Approximate Number Sense Test.