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Hand trying to catch falling object.

Design for Safety activity C3. Find out first-hand how distractions can affect our reaction times.

Activity C3: Distraction [ZIP, 221 KB]

How to use this activity

It’s useful to find out what your students already know. Discuss what they know about reaction time.

What is meant by reaction time? Do they have any ideas about how to measure reaction time?

The measurements taken in this activity are in centimetres. Using a ruler is a useful way of measuring how quickly they react but the measurement in cm is not a reaction time itself, it allows a comparison of reaction time.

Should you want to develop this conversation further – and the maths involved – here is a conversion table adapted from Neuroscience for Kids.


Distance to Time - Reaction Rate Chart


5 cm

10 cm

15 cm

20 cm

25.5 cm

30.5 cm


0.10 sec

0.14 sec

0.17 sec

0.20 sec

0.23 sec

0.25 sec

Neuroscience for Kids - Reflexes(external link)

Try the reaction time test yourself first so you are familiar with the technique. If the 30cm ruler falls before students can catch it then use a metre ruler.

These investigations require students to repeat the technique multiple times. Accuracy, perseverance, and impartiality are all characteristics of scientists worth discussing in class. Impartiality means not wanting to skew the results one way or the other – for example by trying to be the best!

Ask the students to work in pairs to critique the way they carry out this investigation. Questions to help them think about this are:

  • How sure are you of your results?
  • What were the possible shortcomings of this method?
  • How impartial and consistent were you? Was it tempting to be competitive and change the results slightly?
  • How many times was the experiment repeated? Why so many times?
  • How confident are you that the measurements are accurate?
  • Did these results surprise you? In what way?

Where it fits in the New Zealand Curriculum

Nature of Science strand

Investigating in Science – exploring, predicting, defining, analysing.

  • Science activities can be used to develop any of the Nature of Science sub strands.
  • Identify aspects of Investigating in Science that your students need to get better at or understand more fully.
  • Then frame your unit to be very clear about these things when you do them.

NZ Curriculum | Science achievement objectives(external link)

Capability focus

Critique Evidence. 

The five science capabilities (TKI - Science online)(external link)

Contextual strand

Living World, Achievement Objective: Life Processes; recognise that there are life processes common to all living things.

Big science idea

Your brain controls how fast your body can react to a stimulus.


  • Your brain controls your reaction time.
  • If your brain is distracted your body will react more slowly.

Capability concepts

  • Investigations need to be reliable and robust (control variables, repeat trials).
  • Scientists often ask critical questions about how reliable an investigations method is.
  • Strong claims are made from strong evidence.

Possible learning objectives

The students can…

  • explain why it is important to repeat the same test many times
  • use evidence to make a claim about the effect of distractions on reaction time
  • discuss the strengths and weaknesses of their investigation technique.
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