Summary
Introduction
If you write with your right hand, you may also prefer to draw, throw a ball, or eat food with your right hand, but have you ever wondered if your right foot is also more dominant than your left foot? What about your right eye and ear — do you prefer to use them more than your left ones? In this activity, you will get to find out whether people have a sidedness — that is, whether they generally prefer to do activities with one side of their body — and what that might say about their brain.Materials
- Paper
- Pen or pencil
- A coin
- Paper towel tube or toilet paper tube
- A sea shell or phone
- At least 5 volunteers
Prep Work
- Prepare a small data table on a piece of paper to record your results in. Going down the left side of the paper, write "Hand," "Foot," "Eye," and "Ear." Going across the top of the paper, write your volunteers' names.
Instructions
- Ask your first volunteer to write their name on a piece of paper.
Which hand do they write their name with? - Record the result (writing either "Right" or "Left") in your data table in the row labeled "Hand," under the volunteer's name.
- Place a coin on the floor directly in front of your first volunteer. Ask them to step onto the coin. Which foot is used to step on the coin? Record the result in your data table in the "Foot" row, under the volunteer's name.
- Give your first volunteer a paper towel tube or toilet paper tube and ask them to look at a distant object through it. Which eye do they use to look through the tube? Record the result in your data table in the "Eye" row, under the volunteer's name.
- Give your first volunteer a sea shell or phone and ask them to listen to it. Which ear do they put the shell or phone up to?
- Record the result in your data table in the "Ear" column, under the volunteer's name.
- Repeat this process with at least four other volunteers. Be sure to record the results under the new volunteer's name each time.
- Look at your data table, are more of your volunteers right-handed or left-handed? What about right-footed versus left-footed, right-eyed versus left-eyed, and right-eared versus left-eared?
Is one side more common overall than the other?
- How many people that are right-handed are also right-footed (and vice-versa)? What about for the other possible combinations?
Based on your data, do you think people have sidedness or not? Why?
What Happened?
You probably already know that most people are right-handed. Most scientific studies find that between 70% and 90% of people are right-handed. From this activity, you probably saw that most people who are right-handed are also right-sided overall. That is, they usually prefer to use their right foot, eye, and ear as well. But there are certainly exceptions, particularly with eyes and ears. The same trend exists with left-handed people. A person who is left-handed is more likely to also be left-footed, left-eyed, and left-eared. A person's preference for using either their right or left side for each task develops during childhood. But sometimes how a child is taught to do a task can overrule their preferences. For example, if you come across someone who is left-footed, left-eyed, and left-eared but right-handed it is very likely that they were predisposed to be left-handed but taught to write with their right hand in school as a child.
Overall, while around 70% to 90% of the global population is right-handed, it is thought that a smaller percentage is right-footed, an even smaller percentage is right-eyed, and yet an even smaller percentage is right-eared (perhaps a little over half), but this trend is unlikely to be visible using only five volunteers.
Digging Deeper
Each person's brain is divided into two sides, the left and right hemispheres. In some cases, doing a certain activity may make one hemisphere more active than the other. For example, when someone processes language, one hemisphere is usually more active than the other. However, doing this or other activities is not absolutely separated into using one hemisphere or the other, or even certain hemisphere parts. Different brain areas are certainly important for different things, such as speech, hearing, and sight. But if part of a hemisphere is damaged when a person's young, other parts of the brain can often take over doing whatever the damaged part of the brain used to do.
What do the brain's hemispheres have to do with sidedness? As was mentioned, when someone is processing language, one hemisphere is usually working harder than the other. Specifically, when processing language right-handed people usually use the left hemisphere while left-handed people often use the right hemisphere or both hemispheres. Consequently there is some correlation, however limited, between the side(s) we use in our brain and the side we use on our body. This preference to use one side of the body over the other is known as sidedness, laterality, or left/right dominance.
Ask an Expert
For Further Exploration
- In this activity you only used one test to check for dominance in your volunteer's hands, feet, eyes, and ears. Using additional tests would help you check and confirm your results. Can you think of other ways to test for sidedness using objects from around your home? Using other tests, are the results the same as the ones you got doing the original activity?
- If you collect additional data on your volunteers and test more volunteers, you can check your results and also test whether sidedness is linked to another factor. Does the trend in your results hold as you test more volunteers? Do you see a correlation between sidedness and other factors, like age, gender, or being genetically related?
- Sometimes sidedness can run in families. Try to find volunteers from different families and then group your results by family. Do different families have similar or different percentages?
