1. REACTION TIME

2. Learning objectives
understand the nature of response time, reaction time and movement time
understand the role of working memory in choice reaction time
break reaction time down into its component parts
understand the nature of the Hick-Hyman Law
understand the role and effect of probability on choice reaction time
understand the nature of the psychological refractory period
be aware of some of the factors affecting reaction time

3. Response time
Response time is the time from the introduction of a stimulus to the completion of the action required to deal with the problem
It is made up of reaction time plus movement time
Reaction time is the time from the presentation of a stimulus to the beginning of an overt response
Movement time is the time taken to carry out the motor aspects of the performance

4. Response time REACTION TIME MOVEMENT TIME BEGINNING OF RESPONSE
STIMULUS
END OF RESPONSE
RESPONSE TIME

5. Reaction time subdivisions
Reception time
Time for information to pass from peripheral senses to sensory cortices
Opto-motor integration time, which consists of
stimulus identification
stimulus evaluation
motor preparation (preparing the movement to be undertaken)
Motor outflow time
Transmission of information from the premotor cortex to the muscles
Opto-motor integration time is responsible for almost all inter- and intraindividual differences

6. Inter- and intraindividual differences
Simple reaction time (one stimulus and one predetermined response) is faster than choice reaction time (several stimuli and a different response for each stimulus)
With simple RT, stimulus evaluation and motor preparation can take place before stimulus presentation
Hick-Hyman Law
As the number of stimulus-response couplings are doubled, RT is increased
If RT is plotted against the log of the stimulus-response couplings there is a linear increase
Each time RT increases by about 150 ms

7. Probability and reaction time
If a stimulus is likely to occur 90% or 80% of the time it is reacted to faster than when it is likely to occur 50% of the time
Possible reasons:
We focus on most likely stimulus (Alain and Proteau, 1980)
We prepare most likely response (Dillon et al., 1989)

8. Psychological refractory period
When 2 stimuli are presented close together RT to S2 is slower than normal RT
The brain can only deal with 1 stimulus at a time
S2 only begins to be processed during movement time to S1

9. S2 S1 R1 R2
PRP
S1 stimulus 1
S2 stimulus 2
R1 response 1
R2 response 2
PRP psychological refractory period
If S2 is presented <50 ms after S1 the two stimuli can be treated as one.
Practice can not eliminate PRP but can lessen the effect .

10. Stimulus and response factors
Stimulus strength
stronger stimuli elicit quicker RT
Stimulus familiarity
we react faster to stimuli with which we are familiar
Sensory modality
auditory stimuli elicit the fastest reaction times
visual – slowed by time taken to transduce light waves to nerve impulses (electric)
tactile - depends on where the stimulus is applied
Psychological set
Sensory set (focusing on stimulus identification and evaluation) is faster than motor set (focusing on motor preparation)

11. Foreperiods
Foreperiod is the time from the warning signal to the presentation of the stimulus (set then bang in a 100 m race)
Constant foreperiods result in very fast RT
Short foreperiods result in slow RT
person has little time to prepare a response
Long foreperiods result in slow RT
individual can not maintain attention and/or physical readiness

12. Response complexity The more complex the response the slower the RT
Motor preparation takes longer
Stimulus illuminated
When the participant sees that the yellow sign is illuminated, he/she must move their finger from the red button directly to the black (Task 1) or to the black button via the green buttons (Task 2). RT is measured from the illumination of the yellow sign to the lifting of the finger from the red button. RT will be longer for Task 2, even though that initial part is the same in Tasks 1 and 2.

13. Response compatibility
If the stimulus and response are compatible, RT is faster than when they are incompatible
Compatible situation. The blue sign is illuminated, therefore the person has to press the blue button which is on the same side as the blue sign.
Non-compatible situation. Again the blue sign is illuminated, therefore the person has to press the blue button but it is on the opposite side to the blue button. RT will be slower than in the compatible situation.

14. Development and reaction time
RT improves steadily from birth to about 17 years
It plateaus until about 20 years
Then begins to deteriorate
a slow deterioration and nonlinear in nature
increases post-50 years are probably due to decreases in brain blood flow and cell loss particularly in the prefrontal cortex
reception times can be affected by decline of the senses