Thumb War
Is there are correlation between thumb length and winning a thumb war?

scientific method


1. Review the rules of how to declare a thumb war (see below).

Pairs of students will engage in three wars. The winner of the thumb war will be the student that wins 2 out of 3 times. If one student is left handed and one is right handed, the students will engage first in a battle of right hands, then in a battle of left hands. If each contestant wins one of the first two battles, a coin toss will determine which hand will fight the third and final battle.

The two students engaging in a thumb war will sit across from one another at a table. The students will interlock fingers, thumbs facing up. When both students have agreed they are comfortable, they will say "One-Two-Three-Four. I declare a thumb war" while moving their thumbs left and right over one another as they count. Once this is done, the battle shall commence. The object of each battle will be to pin and hold your opponent's thumb down for three seconds. A three second count will be done by the person who has pinned the thumb of their opponent by counting, “one-thousand-one, one-thousand-two, one-thousand-three”.

Students will be expected to:
  • avoid potentially injurious, excessive arm movement,
  • count actual time when timing pin falls (i.e. not speedily in order to win),
  • be honest
  • win or lose gracefully

2. Each student should make a hypothesis about whether they believe the length of a student’s thumb will help their chances of winning. Will the student with the longest thumb win more often? Will the student with the shortest thumb win more often? Is thumb length not a factor when determining who will win or lose a thumb war? Explain the reasoning for your hypothesis.

3. Measure the length of each group members’ thumb and place the information in the table below. To be consistent, have each student straighten the thumb out in a straight line and measure from the start of the proximal phalange of the thumb (at the joint where the thumb connects to hand) to the tip of the thumb (don’t count thumb nails).

Note: the number of wins will be left blank until the next step.

Group Member
Thumb Length (cm)
Number of wins

4. Each member of a group should have a thumb war with all other members. The number of wins of each team member should be recorded in the table above.

5. To get a better data sample and be able to draw better conclusions the experiment should be repeated. Have each member of the group have a thumb war with all other members of the group and add the wins to the table above.

Analyze Data
Answer the following questions:
  • Who had the most thumb war wins? Is their thumb the longest or the shortest of the group?
  • Who had the least thumb war wins? Is their thumb the longest or the shortest of the group?
  • Create a number of wins versus thumb length graph.

Draw Conclusions
  • Does the number of wins depend on thumb length? Give evidence to support your answer.
  • Was your hypothesis confirmed? Why or why not?
  • Make an inference to explain the results of the experiment.
  • What other factors might influence who wins a thumb war?

The focus of this lesson is using the scientific method to solve a problem. Students should come up with their own conclusions about whether thumb length affects how often a person wins a thumb war.

*Adapted from the lesson plan “Teaching the Scientific Method through Thumb Wars” by Shraddha Subramaniam.

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