What is the Approximate Number System?

The approximate number system (ANS) is a cognitive system that supports the estimation and comparison of quantities without relying on language or symbols. Its precision is commonly summarized by a Weber fraction (w), with a smaller w meaning a sharper, less "noisy" number sense.

The ANS plays a crucial role in the development of other numerical abilities, such as the concept of exact number and simple arithmetic. The precision level of a child's ANS has been shown to predict subsequent mathematical achievement in school.

This task is a recreation of the dot-comparison test used by Halberda, Ly, Wilmer, Naiman & Germine (2012), which sampled more than 10,000 participants online and found that ANS precision improves through adolescence, peaks around age 30, and correlates with self-reported school mathematics performance across the entire lifespan.

On each trial, a brief flash of two colors of dots appears (blue and yellow by default — configurable in Settings). Judge, as quickly and accurately as possible, which color had more dots. The ratio between the two quantities varies from trial to trial — your accuracy across ratios is used to estimate your personal Weber fraction.