A group of students investigated the effect of caffeine on how quickly they could react. They measured their reaction times using the ruler-drop test shown ...
Question 1 Report
A group of students investigated the effect of caffeine on how quickly they could react. They measured their reaction times using the ruler-drop test shown in Fig. 7.1, in which one student releases a ruler without warning and the other tries to catch it as quickly as possible. The distance the ruler falls before it is caught can be converted into a reaction time. Each student was tested once before drinking a cup of coffee containing caffeine, and again a short time after drinking it. The reaction times obtained, in seconds, are given in Table 7.1. A student is using the results to work with the data and to think about the nerve pathway involved in catching the ruler.
| Student | Reaction time before coffee / s | Reaction time after coffee / s |
|---|---|---|
| A | 0.28 | 0.24 |
| B | 0.30 | 0.25 |
| C | 0.26 | 0.22 |
| D | 0.32 | 0.27 |
(a) Calculate the mean reaction time of the four students before drinking coffee. [2]
(b) State the effect of caffeine on the reaction times of the students. [1]
(c) Describe how impulses travel from the eyes to the hand muscles as a student catches the falling ruler. [3]
(d) State two variables that should be kept the same to make this a fair test. [2]
Answer Details
This combines a mean calculation with the reflex/nervous pathway. A mean is the sum of the values divided by how many there are.
- (a) \( \text{mean}=\dfrac{0.28+0.30+0.26+0.32}{4}=\dfrac{1.16}{4}=0.29\ \text{s} \) [2].
- (b) Caffeine reduces / shortens the reaction time (the response becomes faster) [1].
- (c) Light stimulates the receptors in the retina of the eye [1]; a sensory neurone carries the impulse to the brain (CNS) [1]; a motor neurone carries an impulse to the hand muscles, which contract to catch the ruler [1].
- (d) Any two: the same distance the ruler is dropped; the same hand used to catch; the same person dropping the ruler; the same amount of caffeine [2].
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