How Can I Be Sure Whether I Am Left-Handed?

About 90 percent of Americans are right-handed, while about 10 percent are left-handed. While most people are pretty confident about whether they are left- or right-handed, there is a surprisingly large number of people who are unsure about their handedness.

So what can you do if you want to be sure whether you are left-handed or right-handed?

For starters, it is important to know that in handedness research, two different forms of handedness are assessed:

• Hand preference refers to whether someone subjectively prefers the left or the right hand for manual activities.
• Hand performance refers to whether someone is actually objectively better in performing specific manual tasks with the left or the right hand (e.g., faster or more accurate).

Testing hand preference

As hand preference is highly subjective, it is commonly assessed by just asking someone about their preferences using a questionnaire. The key here is to look at a wide range of everyday behaviors, not just at writing. While most people identify themselves as left- or right-handers depending on which hand they use when holding a pen during writing, this information might be misleading.

Therefore, psychologists interested in handedness typically use questionnaires that assess multiple types of activities that are performed with the hands. For example, the Edinburgh Handedness Inventory (Oldfield, 1971), the most widely used handedness questionnaire, assesses 10 types of activities. It not only asks about whether someone prefers to write or draw with the left or the right hand, but also about other behaviors, like striking a match or using a spoon. Other questionnaires have even more questions: For example, the Waterloo Handedness Questionnaire assesses 32 different types of activities that are performed with the hands (Steenhuis et al., 1990).

If you want to assess your own hand preference, ask yourself whether you prefer to write with the left or the right hand, but also think of a number of other everyday activities that you typically perform with one hand, such as using a toothbrush, a knife, etc:

• Do you always or mostly use the left hand for all of these activities, not only writing? Then chances are high that you are indeed left-handed.
• If you always or mostly use the right hand, you probably are right-handed.
• If you, however, use one hand for roughly half of the activities and the other hand for the other half activities, chances are high that you are mixed-handed—even if you strongly prefer one hand for writing.

Testing hand performance

While many tasks that are used in psychological departments to test hand performance require more or less complicated laboratory equipment, there is an easy way to test hand performance at home: the handwriting speed test (Provins & Magliaro, 1993).

All you need is a pen, a few sheets of paper, and the stopwatch app on your smartphone. Now, place a sheet of paper in front of you and take the pen in your right hand. Put the pen on the paper and ask a friend or family member to handle the stopwatch app. Once they give you the signal to start, write down the alphabet from A to Z as one word as quickly as possible. Once you are finished with the Z, the other person stops the time and writes it down. Then do the same thing again, but with your left hand. After this, do it two more times with the right and the left hand, so that you have completed three runs with each hand.

Now calculate the average times you needed to write the alphabet with your left hand and with your right hand. Compare the times—which hand was faster?

As you probably expect, left-handers write faster with their left hand, and right-handers faster with their right hand. In the original study by Provins and Magliaro (1993), participants tended to be more than double as fast with their dominant as with their non-dominant hand.