Math Strategy: What is Subitizing? (French and English Videos)

Subitizing: What is It?

Math Strategy: recognizing a quantity without counting each item

Math strand: Number Sense and Numeration


English video:



French version:




Overview:

Subitizing is being able to instantly recognize how many are in a set by looking at them and not counting each item. For most people we can only subitize small sets (less than 5) unless they are in some kind of familiar pattern. For larger sets of numbers, we tend to decompose the set into smaller sets that we can instantly recognize.

We start subitizing small sets of items such as 2 and 3 and recognize and quickly visualize an arrangement as a quantity. This strategy helps children to determine “how many”. When children are shown a variety of dot patterns, some will count each dot and some will be able to identify the number by subitizing. One example is counting the pips on the faces of a die: when you roll a six, the arrangement of pips on the die eventually gets memorized as a quantity of 6 and you don't need to count each pip. Until that arrangement is familiar, one might see this as three rows of two as being equal to six or two columns of three to equal six or other ideas.

Many activities exist to help students subitize. You may decide to show images quickly for a few seconds to imprint this image in the mind versus allowing too much time to count each item. You may put images of quantities on cards like flash cards and flash a card for a few seconds and then put the card down so the students cannot see it anymore. At first you may need to leave the card visible for longer to allow students to count. But remember, the goal is to get students to tell how many without counting (Subitize). How many do you see? How do you see them? are common questions you may ask. TIP: In our video there are two representations of 4. It is important that students understand that a quantity can be modelled in different ways and still be the same quantity. (conservation of number). Similarly, different representations should be subitized such as dots, dots in five-frames, dots in ten-frames, fingers, and tally marks.

How this supports student learning:

Subitizing is fundamental to the development of a strong sense of number. The ability to subitize small numbers helps to minimize the amount of information to be held mentally as well as the amount of work to be done. It is a more efficient way of determining 'how many'. It helps students develop skills, such as unitizing, counting on, and composing and decomposing numbers, all valuable components of number sense.


Where to next?

Provide multiple opportunities to practice and master subitizing of small numbers.

Subitizing activities can be found in the texts, “Number Talks” by Sherry Parrish and “What to Look For” by Alex Lawson, page 190 and the Primary Guide to Effective Mathematics Instruction Number Sense and Numeration http://www.eworkshop.on.ca/edu/resources/guides/Guide_Math_K_3_NSN.pdf


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