Subitizing and Guided Math Groups: Part 1
Subitizing is being able to look at a number and know how many without counting. It refers to “rapid, accurate and confident judgments performed for small numbers of items. It comes from the Latin adjective subitus (meaning “sudden”)” and has to do with immediately knowing how many items one sees for a small set of numbers. When we are talking about larger sets we often estimate or count.
There are two types of subitizing. Perceptual subitizing is looking at the number and knowing how many without any mathematical processes taking place. Conceptual subitizing is based in mathematical processes, such as looking at the parts and the whole. An example of this iswhen you see the eight domino and you know that it is five on one side and three on the other and that makes eight. Spatial patterns are just one kind. Other patterns include kinesthetic ones such as finger patterns, rhythmic and spatial-auditory (Clements, 1999).
We usually teach students to subitize up to ten. See http://www.poweroften.ca/index.php?option=com_content&view=article&id=37&Itemid=103
Spatial arrangements make subitizing easy or hard. Rectangular arrangements seem to be the easiest followed by linear, circular and scrambled arrangements increasing in difficulty (cited Clements, 1999). You can use dot cards, domino cards, number-cube cards and ten frames to teach subitizing. You can also use bingo chips and interlocking cubes.
Subitizing is a fundamental skill in the development of students’ understanding of number (Baroody, 1987). Clements (1999) writes that students can use subitizing to develop understanding of number, conservation and compensation. In part 2 we will discuss this further.