numerosity

Numerosity is the ability to perceive and estimate the number of items in a group without counting each one individually. It’s an innate skill that allows humans and animals to quickly judge quantities, such as recognizing a crowd size or selecting the larger pile of objects. This sense helps us make decisions in everyday life—like avoiding obstacles or choosing the quicker line at a checkout—by assessing amounts efficiently. While it’s not as precise as counting, numerosity provides a rapid, intuitive sense of quantity that underpins more deliberate mathematical reasoning.