Reaction-time determination of the latency between visual signals generated by rods and cones

This paper reports the results of a series of reaction-time measurements in response to light flashes which stimulate preferentially either the rod of the cone receptor mechanisms in human vision. The average response latency between rod- and cone-generated signals as determined from these measurements was found to be 80 ms. Similar response latency values were also obtained from measurements involving only visual responses to real- and apparent-motion stimuli. The results show that the rod-cone response latency, measured by reaction-time or visual methods is relatively constant for target presentation locations between 4 and 9 degrees of visual angle from the fovea along the horizontal.