The nervous system controls & coordinates our reactions to thousands of stimuli each day. Some of these reactions are reflexes, but many are voluntary reactions, responses that are consciously initiated. Reaction time is the time interval from the instant of stimulation to the instant of a voluntary response. All responses result from the formation of impulses by stimulation & the transmission of these impulses along neurons to effectors that bring about the response.

In reflexes, impulses flow over predetermined "automated" neural pathways involving very few neurons, & they do not require processing by the cerebral cortex. In contrast, voluntary reactions involve a greater number of neurons & synapses, & require processing of impulses by the cerebral cortex. Therefore, reflexes have much shorter response time than voluntary reactions.

The reaction time for a voluntary response is the sum of the times required for:

- a receptor to form impulses in a response to a stimulus

- transmission of impulses to an integration center of the cerebral cortex

- processing the impulses in the integration center

- transmission of impulses to effectors

- response by effectors

Do you think people differ in their reaction times to the same stimulus? In this experiment, you will test the null hypothesis that there is no difference in the reaction times of different persons in responding to the same stimulus with the same predetermined response.

MEASURING REACTION TIMES

You will measure reaction time using a ruler and a watch (there are special rulers - called reaction time rulers- for this purpose, but they are unavailable to us)

1. The subject sits on a chair with the experimenter standing facing the subject.

2. The experimenter holds the top of the ruler between thumb and forefinger at about eye level or higher (of experimenter) - we may need to make adjustments to this depending on size of rulers.

3. The subject places the thumb and forefinger of dominant hand about an inch apart and on each side of the bottom of the ruler. The subject's attention is focused on the ruler at thumb level.

4. When the subject indicates s/he is ready, the experimenter, within 10sec, releases the ruler. The subject, seeing the falling ruler, catches it between the thumb and forefinger as quickly as possible.

5. The reaction time is recorded- as closely as possible - use increments on ruler.

(i.e. if drop and catches on 6 first time and on 4 second time - then has been quicker)

6. The test is repeated 5 times and the reaction is averaged. If any reaction is grossly different, discard it and repeat the test to obtain 5 results that are fairly consistent.

RESULTS

- record the 5 results

- calculate your average reaction distance

- Do you think practice and learning will decrease your reaction distance? Repeat the reaction - test 20 times without recording the reaction distance. Then repeat the test 5 times and record your reaction distances.

- calculate your average reaction after practicing the test 20 times.

Did your reaction distance decrease with practice?

State a conclusion from the results.

In what activities is a faster reaction time advantageous?