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Summary of Reference

Clements, Douglas H.

Subitizing: What is it? Why Teach it?

Bibliographic data:
Clements, D. H. (1999). Subitizing: What is it? Why teach it? Teaching Children Mathematics, March, 400-405.

Subitizing (subitising) is the process of determining how many units there are in a group without explicitly counting them.

Early researchers believed that counting or measurement did not imply a true understanding of numbers, but that subitizing did. Implicit was the suggestion that whereas measurement focused on the whole and counting focused on the unit, only subitizing focused on the whole and the unit; therefore subitizing underlay number ideas. Later, researchers in the 1970s and 1980s determined that young children can subitize small number sets without being able to count them and some lines of research suggested that subitizing is a necessary precursor to counting.

There is, however, some dispute over this line of research and conclusion. Other researchers have concluded that subitizing is either a shortcut to counting or a rapid form of counting.

Whichever is correct, it seems that subitizing is an important mathematical skill (involving perception and conception), and one that can be ‘taught’ or ‘promoted’ depending on one’s definition of taught. This paper describes a number of simple classroom activities designed to develop subitizing skills. From there it is a short step to developing ideas about addition and subtraction, and later wider number sense skills, from conceptual subitizing skills.