Test Your Reaction!
What You'll Need
-
A ruler that's 12 inches (30 cm) long
-
A friend
- Reaction time chart (copy this chart on a piece of paper or index card)
![chart for recording reaction times for 2 different people](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/chart/2932268-1-eng-US/chart_full_495.png 428w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/chart/2932268-1-eng-US/chart_full_990.png 428w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/chart/2932268-1-eng-US/chart_full_1468.png 428w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/chart/2932268-1-eng-US/chart_full_1980.png 428w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/chart/2932268-1-eng-US/chart_full_2475.png 428w)
What To Do
![1](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-1/2933319-1-eng-US/number-1_full_495.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-1/2933319-1-eng-US/number-1_full_990.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-1/2933319-1-eng-US/number-1_full_1468.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-1/2933319-1-eng-US/number-1_full_1980.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-1/2933319-1-eng-US/number-1_full_2475.png 110w)
Your friend picks up the ruler with the thumb and index finger.
Make sure that your friend holds the ruler at the end with the highest measurement (12 in) and let it hang freely.
![ruler dangling from a hand](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-1-photo/2932172-1-eng-US/step-1-photo_full_495.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-1-photo/2932172-1-eng-US/step-1-photo_full_990.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-1-photo/2932172-1-eng-US/step-1-photo_full_1468.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-1-photo/2932172-1-eng-US/step-1-photo_full_1980.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-1-photo/2932172-1-eng-US/step-1-photo_full_2475.gif 290w)
![2](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-2/2933331-1-eng-US/number-2_full_495.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-2/2933331-1-eng-US/number-2_full_990.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-2/2933331-1-eng-US/number-2_full_1468.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-2/2933331-1-eng-US/number-2_full_1980.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-2/2933331-1-eng-US/number-2_full_2475.png 110w)
Hold your arm in front of you. Open up your hand and spread your fingers.
Your friend positions the dangling ruler above your hand. Make sure that the bottom edge of the ruler is even with the top of your spread fingers.
![one boy holding a ruler from the top while a second boy has hand at the bottom waiting to catch it](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-2-photo/2932184-1-eng-US/step-2-photo_full_495.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-2-photo/2932184-1-eng-US/step-2-photo_full_990.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-2-photo/2932184-1-eng-US/step-2-photo_full_1468.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-2-photo/2932184-1-eng-US/step-2-photo_full_1980.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-2-photo/2932184-1-eng-US/step-2-photo_full_2475.gif 290w)
![3](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-3/2933343-1-eng-US/number-3_full_495.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-3/2933343-1-eng-US/number-3_full_990.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-3/2933343-1-eng-US/number-3_full_1468.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-3/2933343-1-eng-US/number-3_full_1980.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-3/2933343-1-eng-US/number-3_full_2475.png 110w)
Get ready! Your friend will release the ruler without warning, letting it slip downward.
The moment you see the ruler released, quickly close your hand.
![ruler caught by hand](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-3-photo/2932196-1-eng-US/step-3-photo_full_495.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-3-photo/2932196-1-eng-US/step-3-photo_full_990.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-3-photo/2932196-1-eng-US/step-3-photo_full_1468.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-3-photo/2932196-1-eng-US/step-3-photo_full_1980.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-3-photo/2932196-1-eng-US/step-3-photo_full_2475.gif 290w)
![4](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-4/2933355-1-eng-US/number-4_full_495.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-4/2933355-1-eng-US/number-4_full_990.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-4/2933355-1-eng-US/number-4_full_1468.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-4/2933355-1-eng-US/number-4_full_1980.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-4/2933355-1-eng-US/number-4_full_2475.png 110w)
Still holding the ruler, look at where the top edge of your hand meets the ruler. Record this "measurement" in the Reaction Time Chart.
![recording measurements in a chart](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-4-photo/2932208-1-eng-US/step-4-photo_full_495.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-4-photo/2932208-1-eng-US/step-4-photo_full_990.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-4-photo/2932208-1-eng-US/step-4-photo_full_1468.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-4-photo/2932208-1-eng-US/step-4-photo_full_1980.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-4-photo/2932208-1-eng-US/step-4-photo_full_2475.gif 290w)
![5](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-5/2933372-1-eng-US/number-5_full_495.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-5/2933372-1-eng-US/number-5_full_990.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-5/2933372-1-eng-US/number-5_full_1468.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-5/2933372-1-eng-US/number-5_full_1980.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-5/2933372-1-eng-US/number-5_full_2475.png 110w)
Try this two more times.
Then figure out the average by adding the three measurements and dividing the sum by three. This is the average distance that the ruler dropped before you stopped its fall.
![ruler caught in a hand](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-5-photo/2932220-1-eng-US/step-5-photo_full_495.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-5-photo/2932220-1-eng-US/step-5-photo_full_990.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-5-photo/2932220-1-eng-US/step-5-photo_full_1468.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-5-photo/2932220-1-eng-US/step-5-photo_full_1980.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-5-photo/2932220-1-eng-US/step-5-photo_full_2475.gif 290w)
![6](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-6/2933389-1-eng-US/number-6_full_495.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-6/2933389-1-eng-US/number-6_full_990.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-6/2933389-1-eng-US/number-6_full_1468.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-6/2933389-1-eng-US/number-6_full_1980.png 110w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/number-6/2933389-1-eng-US/number-6_full_2475.png 110w)
Switch roles with your friend and repeat Steps 1 to 5 to find out who's quicker. (The lower the number, the faster you are.)
Practice makes perfect. Try this activity a few more times to improve your reaction time.
![chart filled in with times and measurements](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-6-photo/2932232-1-eng-US/step-6-photo_full_495.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-6-photo/2932232-1-eng-US/step-6-photo_full_990.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-6-photo/2932232-1-eng-US/step-6-photo_full_1468.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-6-photo/2932232-1-eng-US/step-6-photo_full_1980.gif 290w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/brain/test-your-reaction/step-6-photo/2932232-1-eng-US/step-6-photo_full_2475.gif 290w)