(1) A and B two persons make a couple.
B holds a measure scale, and A places his or her fingers at the place of 0 scales of the measure.
A can not touch the scale.
(2)B suddenly releases the scale and then A tries to pick up the measure as quick as possible.
Rough time of taking place of the reaction can refer to the table below.
Distance of measure drops (cm) 10 15 20 25 30
Time required to fall (second) 0.14 0.17 0.20 0.23 0.25
In this case, the nervous system works as following.
eye → sensory nerve → cerebrum → spinal cord → motor nerve → hand muscle
If B makes to call "Yes" when B releases the scale, it becomes a route from the ear.
And the tip of a finger of A is touched to the measure from the beginning. The route from the skin will be examined.