Perceptual latency and spatial frequency.

Subjects estimated the perceived onset of sinusoidal gratings by adjusting a visual probe so that grating and probe were phenomenally simultaneous. The first experiment found that perceptual latency increased by an average of 21 msec over a range of 0.5-9.0 c/deg, or approximately 5 msec per octave of spatial frequency. A second experiment found, that when a fundamental frequency and its third harmonic at one third contrast are compared, a lag of between 21 and 25 msec for the higher frequency lower amplitude grating is obtained. These spatial frequency dependent delays are substantially lower than those reported using other methods.