While “subitizing” may not be a well-known word, it is certainly an important mathematical skill. It is the ability to instantly recognize the amount of objects without actually counting them. Much like the importance of being able to calculate estimates, subitizing is something that comes up in the everyday lives of students. One example is counting the dots on the faces of dice: when you roll a six, chances are you don’t actually count out each of the dots. Rather, you have come to recognize the pattern of three rows of two as being equal to six.
According to The National Council of Teachers and Mathematics, one key part of effective subitizing is developing pattern recognition. Moreover, this mathematical skill allows students to gain a grasp of numbers and advance to higher levels of addition. As an activity, the NCTM suggests taking “snapshots”. Taking snapshots means showing an image of a collection of objects to the student for just a second, then asking him or her to take a mental “snapshot” in order to identify how many objects are included in the image.
As author of Subitizing: What Is It? Why Teach It? Douglas Clements says, “Students can use pattern recognition to discover essential properties of numbers, such as conservation and compensation. They can develop such capabilities as unitizing, counting on, and composing and decomposing numbers, as well as their understanding of arithmetic and place value—all valuable components of number sense.”
Be sure to check out this short video for more information:
Take a look at these subitizing lessons:
Subitizing cards (PDF download)
Here are some great apps for strengthening students’ subitizing and group counting skills: