Clicking on the link below will bring up an image in a new window (you may need to disable pop-up blockers to do this). The picture contains five rows of asterisks. Your job is to count them as quickly as possible. Try using your finger to point and help keep track.

Now try the same task again, only this time, keep your hands flat on the table while you count.

If you’re like most people, this second task was a little more difficult for you. It’s not that you *need* to use your finger to help you count, it just seems to help things along a bit. When you weren’t using your finger to point, you may have found yourself nodding your head to help keep pace with all those asterisks.

A team led by Richard Carlson gave 24 tests like this to 17 students, and verified that pointing to help count asterisks resulted in faster and more accurate counts. But why? Maybe the fact that the items being counted are *all* asterisks tripped up the students, and they had to use their fingers just to keep their place. Carlson’s team repeated the study, only using a variety of different symbols, not just asterisks. They found the same result. Even for a simple counting task, pointing at the things we count makes it easier. But once again the question arises: how is it that simply pointing at things helps us count?

The team repeated the first experiment, but this time they videotaped the students as they completed the task. Once again, half the time the students were allowed to point at the asterisks, and the other half the time they were not.

Two research assistants watched the videos (which were just side-views of the student volunteers’ heads) and noted when they saw the heads nodding. The two assistants agreed on what constituted a nod 87 percent of the time. So how does nodding correspond to pointing and accuracy? Here are some results:

When viewers weren’t allowed to point, they nearly always nodded as they counted. What’s more, non-pointers who nodded were significantly more accurate than non-nodders. It’s beginning to look like the body movements themselves are somehow assisting in the counting process.

Carlson’s team speculates that when we count, we actually use body movements as placeholders — memory aids that improve our ability to count.

In a fourth experiment, they extend this reasoning beyond counting to adding numbers. Volunteers were presented with sets of cubes — real cubes, not images on the computer — printed with numbers from 2 to 6. Each cube had the same number on all sides (e.g. the “2” cube was always a 2; turning it did not affect its value). A computer told the experimenter how many of each cube to present to the volunteers, and also generated a starting value ranging from 7 to 18.

The task was to add up the values of each cube, plus the starting value. So, for example, a participant might see five cubes, valued at 2, 4, 4, 5, and 6, and be given a starting value of 8. The correct response would be 29. The cubes were presented in a small, open cardboard box, and respondents were encouraged to talk their way through the problem. Half the time, they were allowed to touch and move the cubes, the other half the time, they had to keep their hands flat on the table. Here are the results:

For a small number of cubes, being allowed to touch and move the cubes made no difference in the results, but as the number of cubes increased, the effect became dramatic — accuracy plummeted and reaction time increased when students were not allowed to touch the cubes. The students who weren’t allowed to move the cubes also talked to themselves significantly more often as they tried to work through the problems.

Carlson’s team believes that speech may take a similar role to hand movements when doing simple problems like these. Both actions help people keep track of the numbers while they work through the problem. But some of the words used in talking through a problem don’t serve this function. When you say “3 and 3 is 6,” only the numbers serve to help you keep track. The researchers argue that “and” and “is” in this phrase function more like nodding, to keep rhythm as you work.

So using your body, like using your voice, can help you work through arithmetic problems — but some parts of your body help more than others.

Related: Children learn best when teaching is out of sync.

Carlson, R.A., Avraamides, M.N., Cary, M., Strasberg, S. (2007). What do the hands externalize in simple arithmetic?. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33(4), 747-756. DOI: 10.1037/0278-7393.33.4.747