The Human Nervous System (OCR GCSE Biology A, Combined (Gateway Science Suite)): Revision Notes

Aim: To measure and investigate factors affecting human reaction time.

Method:

1. Prepare the Test:

• One person (the subject) should sit on a chair with their forearm resting on the edge of a table so that their hand hangs over the side.
• The other person (the tester) should hold the ruler vertically so that the 0 cm mark is in line with the top of the subject's thumb and forefinger, but not touching them.

2. Conduct the Test:

• The tester releases the ruler without warning, and the subject must catch it as quickly as possible between their thumb and forefinger.
• Record the measurement at the point where the ruler was caught (in centimetres).

3. Repeat and Calculate:

• Repeat the test several times and record all results.
• Calculate the average distance the ruler fell before being caught.
• Use a conversion table (or formula) to convert this distance into a reaction time.

4. Investigate Variables:

• Independent Variable: Change the conditions to test different factors that might affect reaction time. For example:
• Distraction: Have the subject perform a mental task (like counting backwards) while catching the ruler.
• Practice: Repeat the test multiple times to see if reaction time improves with practice.

• Dependent Variable: The reaction time (calculated from the ruler drop distance).
• Control Variables: Ensure that the same ruler is used, and the height at which the ruler is held is consistent.

Data Analysis:

• Record the distance in centimetres and calculate the corresponding reaction times.
• Compare reaction times under different conditions to see how various factors affect them.

Conclusion:

• Analyse the results to determine which factors had a significant effect on reaction time.
• Consider how these results apply to real-life situations where quick reactions are necessary (e.g., driving).

Evaluation:

• Consider the accuracy of the method (e.g., human error in measurement).
• Suggest improvements, such as using a digital timer for more precise reaction time measurement.