Simon task

In psychology, the Simon effect refers to the finding that reaction times are usually faster, and reactions are usually more accurate, when the stimulus occurs in the same relative location as the response, even if the stimulus location is irrelevant to the task. It is named for J. R. Simon who first published the effect in the late 1960s. Simon's original explanation for the effect was that there is an innate tendency to respond toward the source of stimulation.

According to the simple models of information processing that existed at the time, there are three stages of processing: stimulus identification, response selection, and response execution or the motor stage. The Simon Effect is generally thought to involve interference which occurs in the response-selection stage. This is similar to, yet distinct from, the interference that produces the better-known Stroop effect.

In Simon's original study, two lights (the stimulus) were placed on a rotating circular panel. This device would be rotated at varying degrees (away from the horizontal plane). Simon wished to see if an alteration of the spatial relationship, relative to the response keys, affected performance. Age was also a probable factor in reaction time. As predicted the reaction time of the groups increased based on the relative position of the light stimulus (age was not a factor). The reaction time increased by as much as 30%. (Simon & Wolf, 1963).

However, what is usually seen as the first genuine demonstration of the effect that became known as the Simon effect is by Simon & Rudell (1967). Here, they had participants respond to the words "left" and "right" that were randomly presented to the left or right ear. Although the auditory location was completely irrelevant to the task, participants showed marked increases in reaction latency if the location of the stimulus was not the same as the required response (if, for example, they were to react left to a word that was presented in the right ear).

A typical demonstration of the Simon effect involves placing a participant in front of a computer monitor and a panel with two buttons on it, which he or she may press. The participant is told that they should press the button on the right when they see something red appear on the screen, and the button on the left when they see something green. Participants are usually told to ignore the location of the stimulus and base their response on the task-relevant color.

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