Required Practical 06: Reaction Time

About this practical...

This is a very simple experiment that can be used to incorporate lots of other parts of biology and experimental science. You will basically drop a ruler through a student's open hand. When they see it fall, they grab it. This allows you to calculate means, spot anomalies, compare data and to even calculate time using S=ut + ½at2. You can also use this to test hypotheses like "does caffeine increase reaction rate?" and complete a double blind trial.


1. In groups, select a person to be the tester and the person to be tested.

2. The tester holds a metre rule above the open hand of the person being tested. Both people should look at the hand of the person being tested so that there are no clues as to when the ruler is going to be dropped.

3. The tester lets the ruler drop and the person being tested must close their hand around the ruler to catch it. The distance that the ruler falls (in cm) can be converted into seconds.

4. Repeat this many times and record each reaction time into a table. Swap roles and repeat so that the reaction time of all students can be recorded.

This experiment will allow you to look into the medical trial process too. Once everyone has a "baseline" result, everyone in the class can be given a drink. I provide two trays of drinks, one is diet cola and one is caffeine free diet cola (red cups and white cups. Students are not told which is which. Buy a cheap brand that does not have a distinctive taste - CHECK FOR ALLERGIES etc). After drinking a cup, I discuss that caffeine is supposed to speed up your reactions and students can see if they can work out which.

When complete, look at how robust the method is and look at how it compares with a double blind trial.

Safety & Managing Risks

Although there is no need for any chemical, biological or electrical risk awareness for the main experiment here, ensure that the environment is free from trip hazards etc. The main area of concern is drinking in the lab - double check for allergies and ensure that there is no way for the drink to become contaminated. For more detailed information, please consult CLEAPSS.

Technician notes:

Meter rules (if requested, ones with reaction times overlay applied)

Teacher may request anonymised drinks - ensure hygiene

This page was updated on: 8th January 2022