## The Placebo Effect: Do You Believe Your Teacher?

Tests To Do!

How fast do your nerves send and receive messages? Involuntary reflexes are very fast, travelling in milliseconds. The nerve impulses in the neurons that control these reflexes act without even bothering to be processed by the brain! In fact, the fastest impulses reach 520 kilometres (320 miles) per hour! Our conscious muscular response to a stimulus takes a much longer route. See just how fast your brain and nerves respond to stimuli in this experiment.

#### Method

This activity is designed to measure your reaction time in catching a dropped metre ruler.

1. Sit with your forearm on a table surface so the hand extends over the edge.

2. Have your partner hold the metre stick with the zero end just above, but not touching, your thumb and fingers.

4. Catch the stick as quickly as you can between your thumb and fingers.

5. Record the centimetre mark where you caught the stick.

6. Repeat steps 3, 4 and 5 ten times. Have your partner vary the waiting time before each drop. Record the results on a chart.

7. Cross out the highest and lowest numbers on your chart, so only eight numbers are left. Find the mean (average) of these numbers and record it.

8. Repeat this experiment with your partner catching the stick. Record the results.

9. Convert the distance into your reaction time with the chart below.

Here is a table to convert the distance on the ruler to the reaction time. For example, if you caught the ruler at the 20 cm mark, then your reaction time is equal to 0.20 seconds (200 ms). Remember that there are 1,000 milliseconds (ms) in 1 second.

Distance on ruler Time
5 cm 0.10 s (100 ms)
10 cm 0.14 s (140 ms)
15 cm 0.17 s (170 ms)
20 cm 0.20 s (200 ms)
25.5 cm 0.23 s (230 ms)
30.5 cm 0.25 sc (250 ms)
43 cm 0.30 s (300 ms)
61 cm 0.35 s (350 ms)
79 cm 0.40 s (400 ms)
99 cm 0.45 s (450 ms)