Exercise 4.1: Measuring your Reaction Time

Experiment Time - Measuring your Reaction Time

In the following experiment you will measure your reaction time by measuring the distance a meter stick falls through your fingers before you can stop it. You will need the help of another person to carry out this experiment. If you don't have a meter stick, use a small piece of wood and then use a ruler or measuring tape to measure the distance the stick fell.

Problem: What is your reaction time when catching a dropped meter stick?

Hypothesis: (an educated guess at the answer) How far do you believe the stick will fall through your fingers before you stop it.

Experimental Design: Your reaction time is the manipulated variable, while the distance the stick travels is the responding variable. A control is any part of the experiment that stays the same as the procedure is tried again and again. In this case the controls would be how you are sitting, where you are placing you hand and fingers, the way the other person drops the stick - you get the idea. Procedures 2 - 9 are controls.


1. Read through the entire procedure before you start.
2. Sit at a table so that your arm rests on the table and your hand is out over the edge.
3. Hold your thumb and forefinger about 3 cm apart.
4. Keep your eye on the end of the stick.
5. Have the other person hold the bottom of the stick even with the opening in your
6. Predict how far it will fall.
7. Your partner will drop the stick without notice.
8. You will close your thumb and forefinger as quickly as you can.
9. Measure the distance between the end of the stick and where you caught it.
10. Record your prediction and actual measurement in the table below.
11. Repeat the procedure four more times.


Trial Number
Predicted Distance
Distance Stick Drop
Average distance stick drops in cm:
Sum of drops divided by 5 =
Sum of drops divided by 5 =


1. 1. What was the difference between your first prediction and the actual drop distance. Why do you think they different?
2. Did the drop distance in cm decrease each time you did a trial? If your answer was yes, try to explain why that happened.
3. How accurate were your measurements for each trial?
4. Explain where reaction time could be important in day-to-day living.

Further Expermimentation

1. a) What problems occurred during the experiment? For example, did you manage to maintain the 'controls' during the various trials or did some of them change? (Review the list of controls in the procedure.)
b) List the controls you used as well.


2. If you were to do the experiment again, how would you change the procedures?