IRIS Pigmentation and Reactive Motor Performance

Worthy's (1974) hypothesis that brown-eyed subjects respond faster than blue-eyed subjects on reactive motor tasks was tested. Experiment 1 compared dark-brown and blue-eyed subjects on rotary pursuit and choice response time tasks. There was a tendency for the predicted effect, but it was only evident for choice responding where speed was the principal performance criterion. In Experiment 2 iris pigmentation effects were found to be limited to the reaction-time component, but not the movement time component, of a simple motor response. Differences in the filtering of lightwaves and in CNS neuro-pigmentation are mechanisms commonly used to explain these findings. Iris pigmentation effects were found for both auditory and visual stimuli, thus supporting the neuro-pigmentation explanation.