Question

First, give one real-life example for each of these reaction types. Then, explain which type declines more with normal aging, and why.

"simple" reaction time (one stimulus -> one response) e.g. a light changes color (stop or go)

"choice" reaction time (two stimuli -> choosing tow different responses) e.g. noise or ight (light hand or foot)

Answer 1

Reaction time is the time elapsed between the onset of a suddenly presented and unanticipated signal to the beginning to response to it or it measures ability to quickly respond to stimulus. It reflects the time it takes to receive, interpret a stimulus, get information from memory or decide and to initiate a response to it.

Stimulus -> Sensory Neuron -> Spinal Cord or Brain -> Motor Neuron –>Response

It important in many sports and day to day activities. Measurement of reaction times is one of the fundamental concepts in cognitive psychology.

Simple reaction time (SRT) is minimal time taken to respond to single stimulus.

Example: SRT is required –

· Crossing road at zebra crossing when traffic light is red for vehicles.

· when a track runner accelerates in response to the starting gun,

· or when a driver accelerates in response to a green light.

Choice reaction time (CRT) is minimal time taken to respond to two or multiple stimuli.

For example:

· At the times of power cut, when traffic lights are not in order then deciding according to whistle blown by and hand signals of traffic police man (three stimuli traffic lights not giving proper signal, sound of whistle, hand signals).

· In a football match a player receive stimuli from the eyes (position of other players, the ball etc), the ears (calling from players, the referee, even spectators), and kinaesthetic sense (the performer's position, their options etc). The more choices a person has, the more information needs processing, and the longer it takes to process, a slower reaction time is recorded. Skilled player reduces reaction time by selecting the most important information, and by anticipating other players actions and the path of the ball quickly.

Simple reaction time depends on nerve connections and signal pathways, is 'hard wired' in your body composition and cannot be improved. Another type of reaction time, choice reaction time, is the time taken between stimulus and action which requires a choice. Choice reaction time can be improved by practice and training.

Reaction time also becomes more variable with age. Both simple and complex reaction time declines with age but decline is more marked for complex reaction time.

· Simple reaction time shortens from infancy into the late 20s, then increases slowly until the 50s and 60s, and then lengthens faster as the person gets into his 70s and beyond.

· Age effect is more marked for complex reaction time tasks

Variability in older adults was usually associated with multiple factors: -

· Age related changes in body affects neural integrity. Older adults have more cross-communication occurs between two cerebral hemispheres through corpus callosum, which can act as either a bridge or a dam between brain hemispheres. This cross communication is very important during two-sided motor skills and certain cognitive functions, but one-sided motor skills requiring strong focus from only one side, the corpus callosum switches roles and serves as a sort of dam between hemispheres. With age, breakdowns in the corpus callosum occur, breaking down the dam effect, and causing more cross-talk to occur between hemispheres, even when it’s not required or during rest also. It is undesirable as the opposite side of the brain controls the part of the body that is moving. So, when both sides of the brain communicate simultaneously while only one side of the body tries to move, confusion and slower responses result.

· Reflexes slows down with age. Physical changes in nerve fibres slow the speed of conduction and the parts of the brain involved in motor control lose cells over time. This effect of age on reflexes and reaction time varies greatly from person to person.

· Changes in sensory perception like poor vision, decreased hearing capacity, reduced mobility may also slower recognition of stimuli.

· Behavioural tendency of older people to be more careful and monitor their responses more thoroughly. When troubled / distracted older people also tend to devote their exclusive attention to one stimulus, and ignore another stimulus, more completely than younger people.

· Other factors which affect reaction time in elderly and are responsible for variation in reaction time among people of same age group are gender, dominant hemisphere - left or right, practice and training, exercise, distraction, alcohol, punishment, stress, anxiety, personality type, use of stimulant drugs, and illness. The most important thing is many of them are modifiable.