This was not in and of itself evidence for a relationship between S–R compatibility and reaction time; an alternate hypothesis posited that the delay was simply the result of the sensory information taking longer to reach neural processing centers when hemispheres are crossed.
This alternate hypothesis was disproven by a follow-up trial in which Fitts and Seeger had subjects cross their arms, so that the left hand would press the right button and vice versa; the difference between reaction times of subjects in the standard and crossed-arms trials was statistically insignificant, even though the neural signal traveled a greater distance.
[2] The reverse scenario was tested in a 1954 experiment by Richard L. Deninger and Paul Fitts, in which it was demonstrated that subjects responded more quickly when the stimulus and response were compatible.
[5] In 2000, T. E. Roswarski and Robert Proctor conducted a variation of the original Fitts and Seeger experiment involving auditory tones in each ear instead of lights.
[8] In 1998, Mike Tucker and Rob Ellis conducted an experiment at the University of Plymouth which expanded the concept of S–R compatibility to higher-order cognition.
In their experiment, subjects were given two buttons, one on their left and one on their right, and shown a series of pictures of familiar objects like frying pans and teacups.
As another example, red lights are universally associated with "stop" and green with "go", and a reversed configuration will result in a longer reaction time.