Subitizing

Subitizing is the rapid, accurate and effortless ability to perceive the number of items in a small set, typically four or fewer, without counting or otherwise relying on language or arithmetic. Within that range a person can state a set size almost instantly. Sets larger than about four or five items generally cannot be subitized unless they form a familiar pattern, such as the dots on a die. The term was coined in 1949 by psychologist E. L. Kaufman and colleagues, from the Latin subitus, meaning sudden. Measured reaction times confirm the distinction: judging a quantity outside the subitizing range costs 250 to 350 milliseconds per additional item, while judging one inside the range costs only 40 to 100 milliseconds per item. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/