Subitizing: What is It?

Subitizing is when students can recognize a quantity without counting each item, rather visually recognizing the set.

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. This is called 'perceptual' subitizing. For larger sets of numbers, we tend to decompose the set into smaller sets that we can instantly recognize and add together. This is called 'conceptual' subitizing.

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 a variety of smaller groups of pips (ex: three rows of two as being equal to six or two columns of three to equal six).

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?' and '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.

Supporting Students to Subitize

Throughout classroom experiences, students will have many opportunities to subitize in the real world. When we randomly ask students 'how many' of an item there are, they are working to subitize either perceptually or conceptually, depending on the size of the set. As students engage in play, educators can strategically pose questions about their toys they are playing with. For example, when playing with the colored blocks the teacher might cover a small set with a paper and ask "how many blocks are there?" Quick reveals of the sets are a fun way to turn this concept into a game!

Games & Activities to Support Subitizing:

Where to Next?

Once students are confident with subitizing, they can be encouraged to move toward more efficient strategies such as Counting Three Times or Counting On.