HOMEOSTASIS: RP7/reaction time

• Measuring a person's reaction time

  1. Person 1 sits on a stool with good upright posture

  2. Person 1 places the forearm of their dominant arm across the table with hand overhanging the edge

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

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

  5. Person 2 drops the ruler at a random time

  6. Person 1 catches the ruler with thumb and first finger as quickly as possible

  7. Person 2 records the measurement on the ruler level with Person 1's thumb

  8. Repeat the test several times and calculate the mean
• Reaction time


  The time taken for a person to respond to a stimulus
• The two people then switch places with Person 1 testing the reaction time of Person 2
• Independent variable


  The variable that is changed in an experiment
• Dependent variable


  The variable that is measured for each change in the independent variable
• Control variables


  • Variables that are kept constant to avoid affecting the dependent variable
  • Examples: distance between thumb and first finger, measuring at top of thumb, room conditions
• Practicing catching the ruler

  Reaction time becomes shorter
• Using dominant hand vs non-dominant hand


  Reaction time is shorter with dominant hand
• Consuming caffeine before the test


  Reaction time may change
• Need to check for any medical issues that could be affected by caffeine
• The test should be carried out in a lab where hazardous chemicals are not normally used