thumb|An observer may be able to instantly judge how many red circles are present without counting them, but would find it harder to do so for the greater number of blue circles. Subitizing is the rapid, accurate, and effortless ability to perceive small quantities of items in a set, typically when there are four or fewer items, without relying on linguistic or arithmetic processes. The term refers to the sensation of instantly knowing how many objects are in the visual scene when their number falls within the subitizing range.
thumb|An observer may be able to instantly judge how many red circles are present without counting them, but would find it harder to do so for the greater number of blue circles. Subitizing is the rapid, accurate, and effortless ability to perceive small quantities of items in a set, typically when there are four or fewer items, without relying on linguistic or arithmetic processes. The term refers to the sensation of instantly knowing how many objects are in the visual scene when their number falls within the subitizing range.
Sets larger than about four to five items cannot be subitized unless the items appear in a pattern with which the person is familiar (such as the six dots on one face of a die). Large, familiar sets might be counted one-by-one (or the person might calculate the number through a rapid calculation if they can mentally group the elements into a few small sets). A person could also estimate the number of a large seta skill similar to, but different from, subitizing. The term subitizing was coined in 1949 by E. L. Kaufman et al., and is derived from the Latin adjective subitus (meaning "sudden").
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).