REACTION TIME

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

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

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

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

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

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)

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

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 .

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)

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

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.

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.

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