The brain

• Measuring a person's reaction time


  1. Person 1 sits on stool with good posture

  2. Person 1 places dominant arm across table with hand overhanging

  3. Person 2 holds ruler vertically with 0 cm mark between Person 1's thumb and first finger

  4. Person 2 tells Person 1 to prepare to catch ruler

  5. Person 2 drops ruler at random time

  6. Person 1 catches ruler with thumb and first finger

  7. Person 2 records measurement at top of Person 1's thumb

  8. Repeat test several times and calculate mean

  9. Switch roles, Person 1 tests Person 2's reaction time
• Independent variable


  The variable that is changed (the person having reaction time tested)
• Dependent variable


  The variable that is measured (the reaction time)
• Control variables

  • Constant stick working distance between thumb and first finger
  • Measure ruler at top of thumb
  • Keep conditions in room the same (lighting, background noise)
• Changing control variables could affect the dependent variable (reaction time)
• Other independent variables that could be investigated:
• Investigating effect of practice


  One person catches ruler many times, see if reaction time changes
• Investigating effect of hand used

  Test with dominant hand, then non-dominant hand of same person
• Investigating effect of caffeine

  1. Test subject drinks measured amount of cola 30 mins before, compare to normal reaction time

  2. Also test with caffeine-free cola
• Need to check test subjects have no medical issues affected by caffeine
• Tests should be carried out in lab where hazardous chemicals are not normally used