Subitizing: What is it? Why teach it?

Three pictures hang in front of a sixmonth-old child. The first shows two dots, the others show one dot and three dots. The infant hears three drumbeats. Her eyes move to the picture with three dots.

Young children spontaneously use the ability to recognize and discriminate small numbers of objects (Klein and Starkey 1988). But some elementary school children cannot immediately name the number of pips showing on dice. What is this ability? When and how does it develop? Is it a special way of counting? Should we teach it?

Subitizing: A Long History

Subitizing is "instantly seeing how many." From a Latin word meaning suddenly, subitizing is the direct perceptual apprehension of the numerosity of a group. In the first half of the century, researchers believed that counting did not imply a true understanding of number but that subitizing did (e.g., Douglass [1925]). Many saw the role of subitizing as a developmental prerequisite to counting. Freeman (1912) suggested that whereas measurement focused on the whole and counting focused on the unit, only subitizing focused on both the whole and the unit; therefore, subitizing underlay number ideas. Carper (1942) agreed that subitizing was more accurate than counting and more effective in abstract situations.

In the second half of the century, educators developed several models of subitizing and counting. They based some models on the same notion that subitizing was a more "basic" skill than counting (Klahr and Wallace 1976; Schaeffer, Eggleston, and Scott 1974). One reason was that children can subitize directly through interactions with the environment, without social interactions. Supporting this position, Fitzhugh (1978) found that some children could subitize sets of one or two but were not able to count them. None of these very young children, however, was able to count any sets that he or she could not subitize. She concluded that subitizing is a necessary precursor to counting. Certainly, research with infants suggests that young children possess and spontaneously use subitizing to represent the number contained in small sets and that subitizing emerges before counting (Klein and Starkey 1988).

As logical as this position seems, counterarguments exist. In 1924, Beckmann found that younger children used counting rather than subitizing (cited in Solter [1976]). Others agreed that children develop subitizing...