Investigating Reaction Time

Investigating Reaction Time

What Is Reaction Time?

Reaction time is the time it takes to respond to a stimulus. It involves a stimulus → nervous system → response.

💡 Key Concept: Reaction times can be affected by factors like caffeine, fatigue, distraction, and practice.

The Ruler Drop Test – Measuring Reaction Time

Apparatus Needed

✔ A 30cm ruler
✔ A partner
✔ A table and chair
✔ Optional: Caffeine source (e.g. energy drink), stopwatch

Method

1️ One person sits with their arm resting on a table.
2️ Hold a ruler vertically above their hand with the 0cm line level with their thumb.
3️ Without warning, drop the ruler.
4️ The person catches the ruler as quickly as possible.
5️ Record the measurement where their thumb catches the ruler (in cm).
6️ Use a conversion table or formula to convert the distance into reaction time.
7️ Repeat several times and calculate an average.
8️ Swap roles and repeat (e.g. before and after drinking caffeine).

👉 Suggested Image: A diagram of the ruler drop test setup.

Optional Extensions

✔ Test the effects of caffeine, talking, or phone use on reaction time.
✔ Compare results between different age groups or genders.

Variables in the Experiment

Variable Type

Example

Independent

Caffeine intake or distraction level

Dependent

Reaction time (distance the ruler falls)

Control

Same ruler, same hand, same conditions

Questions 

  1. What does reaction time measure?
  2. What is the dependent variable in the ruler drop test?
  3. Name two factors that might affect reaction time.
  4. Why do we repeat the test and take an average?
  5. How can you improve accuracy in this test?

Summary 

  • Reaction time is the time between a stimulus and a response.
  • It can be measured using the ruler drop test.
  • Reaction time is affected by factors such as caffeine and distractions.
  • Ensuring a fair test involves controlling variables and repeating trials.