Approximate number system

The approximate number system (ANS) is a hypothetical physiological basis for the intuitive "number sense". As its name suggests, it only provides an approximate sense of number, and is not an accurate symbolic computation system. There is some evidence that the ANS is capable of simple operations such as addition and is also present in non-human animals.

Some research results suggest that the functioning of the human ANS may involve the intraparietal sulcus of the brain. Children with developmental dyscalculia were found to have less gray matter in the left intraparietal sulcus.