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Thumbs Up for the Thumb
By John Cowens
This digit enables us to "get a grip" like no other primate on the planet! But what happens when we try to do without it?
Online Extra: For the list of materials needed for this activity and the data table click here.
Want to write with a pen or pencil, or button your favorite jeans? Tasks that employ fine motor skills are often "all thumbs."
Long ago, I played basketball on my high school team. When my ball-handling skills were unacceptable, which was often, the coach would blow his whistle at me and yell, "You're all thumbs! Concentrate!" Now that I've had more than 30 years to think about the coach's thumb idiom, I realize that the thumb is an important digit…especially in playing basketball.
The incredible opposable thumb
Apes and primates are able to grab objects with more efficiency due to their opposable thumbs. A human can easily fold the "pinky" and "ring" fingers across the palm to meet the thumb, as well as complete delicate tasks such as grasping objects. Interdigital grips might also include the tips of thumb and index finger (holding a piece of candy) or thumb and sides of the index and third finger (holding a pencil).
Human thumbs are so important for gripping that during the Gallic wars, Julius Caesar ordered the thumbs of captured warriors amputated, which made it almost impossible to bear arms. This practice was later used in a number of wars and in the slave trade.
Let's have a thumb war
Challenge your students to complete a variety of tasks (using a doorknob, picking up small objects, writing their names, unscrewing a jar lid, etc.) without using their thumbs.
Procedures:
- Instruct students to observe their hands while moving their thumbs in a number of directions.
- Ask students to perform various tasks (buttoning clothing, picking up a dime, etc.) while paying attention to the involvement of their thumbs. (Click here for a data table that includes the complete list of tasks as well as space for rating the difficulty of the tasks.)
- Record each task's level of difficulty using the following rating scale: 1 = very difficult, 2 = difficult, 3 = easy, 4 = very easy. Record the time it took to complete the task. If the task takes longer than five minutes, write "U" for unsuccessful. Record the level of thumb involvement for each of the tasks using the following rating scale: 1 = thumb not needed, 2 = thumb slightly used, 3 = thumb used throughout the task, 4 = extensive thumb usage.
- Have the students help each other use masking tape to tape their thumbs to the side of their hands. Be careful not to wrap the tape so tightly that blood is unable to circulate.
- Repeat the same tasks with taped hands. Pay attention to any difference in the performance of the tasks. Enter observations on the data table.
Looking at the results
The least amount of thumb involvement is required for tasks like writing with a marking pen on a large piece of paper, zipping a zipper or picking up a chair. The most thumb involvement is required for tasks like writing with a pen or pencil, buttoning jeans or picking up coins. Tasks that use fine motor skills tend to involve the thumb. Much human technological development has been directly linked to the thumb and the fine motor skills dependent on it. The use of tools, surgical skills, any skill that requires manipulating small objects depends on the use of the opposable thumb.
Questions
- Were the tasks more difficult with or without an opposable thumb?
- How did you adapt your "normal" handling techniques without the use of your thumbs to perform each task?
- Which tasks required the least amount of thumb usage? Which required the greatest?
- Of the tasks performed, which used fine motor skills (those requiring small hand movements) and which used gross motor skills (those involving larger movements using arm and back muscles)? Is there a correlation between thumb use and the type of motor skills involved?
- Explain why you do or do not believe that the opposable thumb has helped humans adapt to their environment and survive.
Extensions
Ask your students to write about how our lives would be without thumbs. How might the design of tools, utensils, clothing, shelter, etc. be altered? How might sports be different? How might transportation be different?
Draw and describe an invention for thumbless hands that would help us perform everyday activities.
Online explorations
Online Extra: For the list of materials needed for this activity and the data table click here.
John Cowens teaches science at Fleming Middle School in Grants Pass, OR.
