Sunday, April 27, 2008

Subitize


Alex the parrot


Every once in a while, I come across a word that is new to me, usually something totally out of my field. This one comes from psychology, but it has worked its way into math discussions.

The verb is subitize, and the noun subitization has also been formed. It means to correctly perceive the exact number in a small set without actually counting. The Italian word subito means “at once,” and it is a descendant of the Latin subitus, sudden and unexpected.

The Oxford English Dictionary tells us precisely where the word came from in a 1949 citation of E. L. KAUFMAN et al. in American Journal of Psychology, LXII. 520: “A new term is needed for the discrimination of stimulus-numbers of 6 and below... The term proposed is subitize... We are indebted to Dr. Cornelia C. Coulter, the Department of Classical Languages and Literatures, Mount Holyoke College, for suggesting this term.”

Here is the word in context:

“The infantile sense of numbers is restricted to collections of only four or five objects, and the data suggests that infants and adults manipulate such collections using a mental process quite distinct from counting. For small collections, both adults and infants perceive the "numerosity" of the collection directly, somewhat like we perceive shape or color. This direct, intuitive perception of numerosity is called subitization, and it is the first number skill that we develop. When we see three objects, we don't count "one, two, three," instead we are simply aware of the group's "threeness." Most people can subitize up to seven or eight objects, switching to a variety of counting strategies for larger collections.” [Number Blindness: A Hidden Challenge for Mathematics by Ashish Ranpura]

Someone named Al has even created a game that utilizes “subitize.”

Sidebar: Subitizing: What Is It? Why Teach It? By Douglas H. Clements



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