Perceptual latencies to sinusoidal gratings

Simple visual reaction time (RT) to suprathreshold sinusoidal gratings was determined as a measure of perceptual latency. As parameters, spatial frequency, exposure duration and modulation were varied. With three subjects, RT was found to increase with increasing spatial frequency. High contrast gives shorter RTs than low contrast. In the range investigated the effect of contrast is small compared with that of spatial frequency. At constant spatial frequency exposure durations of 30-60 msec produce shortest RTs. Underlying physiological mechanisms are considered. Some evidence comes from different temporal behaviour of X- and Y-system but central mechanisms are also supposed to be involved.