Practical activity

Plan and carry out an investigation into the effect of a factor on human reaction times

You can carry out a number of investigations to determine the effect of a specific factor on human reaction times.

A suitable investigation could be the effect of caffeine or the amount of background noise in the room. A simple method to measure the effect is to use the ruler drop test.

Ruler drop test

  1. Work with a partner.
  2. Person A holds out their hand with a gap between their thumb and first finger.
  3. Person B holds the ruler with the zero at the top of person A's thumb
  4. Person B drops the ruler without telling Person A and Person A must catch it.
  5. The number level with the top of person A's thumb is recorded in a suitable table. Repeat this five times without background noise and five times with background noise.
  6. Swap places, and record another ten attempts.
  7. You can use the conversion table to help convert your ruler measurements into reaction time or just record the catch distance in cm.
On the left-hand side two hands hold both end of a ruler from top to bottom. On the right hand side one hand has just let go and the second hand at the bottom has caught ruler.
DistanceTime
1 cm50 ms
5 cm90 ms
10 cm140 ms
15 cm170 ms
20 cm200 ms
25 cm230 ms
30 cm250 ms

Example results:

AttemptDistance on ruler with noiseDistance on ruler without noise
125 cm18 cm
238 cm15 cm
336 cm22 cm
431 cm24 cm
538 cm13 cm
Question

What effect does noise have on the speed of reaction, measured in centimetres? [2 marks]

There is a clear difference between length of ruler that passed through the fingers before they managed to catch it, with and without noise. [1 mark]

For example, the first set of data, with noise – 25 cm compared to without noise – 18 cm. It suggests that noise reduces the response times of the person in this experiment. [1 mark]

Tip: include at least two or three sets of data from the results.