Simple reaction time to sinusoidal grating and perceptual integration time: contributions of perceptual and response processes.

For sinusoidal gratings, two experiments were carried out to examine relation between simple reaction time and perceptual and response processes. First, the simple reaction time (RT) was measured as a function of grating contrast with spatial frequency as a parameter. Second, contrast threshold was determined as a function of exposure duration (ED). On the basis of the RT-contrast function and the ED-contrast threshold function empirically obtained, the difference between the RT and the ED was evaluated as a function of grating contrast. The RT-ED difference, in which the perceptual integration time was eliminated, was considered to reflect the transmission time, delay in the response process, and delay in the motor response. As the grating contrast increased, the RT-ED difference decreased rapidly at first, and then gradually, and finally leveled off. The RT-ED difference vs contrast function depended on spatial frequency. Based on the analysis of the characteristics of the RT-ED functions, the effects of grating contrast and spatial frequency on the simple RT could be ascribed to the changing contributions of the perceptual and the response processes.