Hicks law states that reaction time increases as the number of available options increases, though the increase in reaction time decreases as more options are added (1). The brain has limited capacity to process multiple tasks simultaneously, leading to worse performance on each task (2). If a second stimulus is presented shortly after a first, reaction time to the second is significantly slowed due to the brain still processing the first stimulus (3).

1. Hicks law states that the greater the number of possibilities
available to a performer the longer it takes for them to react.
This acts in a curved continuum, meaning
that as the number of possibilities
increases the step up in reaction time
decreases.
E.g.
Simple/1 choice=low reaction time
2 choices = much higher reaction time than 1 choice.
3 choices = slightly higher reaction time than 2 choices.
4 choices = not much higher reaction time than 3 choices.
The biggest jump is 1 to 2 options as this is where there
is a decision added into the reaction time.
1

2. The brain has a limited capacity for processing information. As
we try to do more than one thing at once our performance in
doing them suffers.
One theory of why this happens is Single Channel Hypothesis.
This means that the brain only has one channel for processing
information which must continually switch between tasks if this
is required.
A different take on the same theory is Multi Channel
Hypothesis. This means that the brain has several channels
each dedicated to a different task, so performance only suffers
if two similar tasks are attempted.
Walking and talking = easy
Bouncing 2 balls = hard
2

3. If we encounter a stimulus we react to it quickly.
If a second stimulus is presented quickly after the first our
reaction time is significantly slowed.
It is thought this is because we are still busy dealing with the
first stimulus.
3
First stimulus First response
Second
Stimulus
Second
Response
PRP
It should be noted that if two stimuli are presented very close
together (less than 50 microseconds), the two tend to be
grouped together and processed simultaneously avoiding PRP.
(McMorris 2004)