Assessment of eye dominance through response time

The present study examined the effectiveness of a new technique for the assessment of eye dominance. 41 undergraduates of both sexes completed the Edinburgh Handedness Inventory, as well as two conventional performance indexes of eye dominance. Then each subject was positioned before the video monitor of a microcomputer and asked to view the monitor through a device that presented a different area of the monitor screen to each eye. In these two screen areas the digits 0 through 9 were randomly presented. Within every three trials the first two trials presented a digit to both eyes, and on the third trial a digit was presented to both eyes or to only one eye. There were 20 presentations of each kind: to both eyes, right eye, or left eye. The subject indicated whether the viewed digit was larger than or less than 4.5. This cognitive decision task was a constant in all trials. Analyses were performed on the third-trial response times, specifically, on the response time using right eye minus response time using left eye. For right-eyed people this was a positive number. As predicted, handedness, as assessed by the Edinburgh instrument, was significantly correlated with eyedness, as assessed by the response time procedure. The two conventional indexes of eyedness were also correlated with eyedness as assessed by the response time procedure. This procedure, then, provides a cardinal-scale measurement of degree of eye dominance.