One of the basic goals of the present study was to establish whether variation in simple reaction time (RT) can be explained in terms of the simple cone-opponency model described earlier or whether it reflects the higher-order mechanisms known to operate at cortical levels. Many studies have been undertaken to examine the influence of color on the simple RT.
17 18 19 20 21 22 23 24 In some of these, RT has been shown to be independent of wavelength,
17 19 20 but this has tended to occur when chromatic stimuli have been confounded with luminance increments
19 20 embedded within a surround
17 or flickered at fast temporal rates (≥15 Hz).
24 Better isolation of the chromatic visual system is achieved by the use of selective adaptation
21 or equiluminant stimuli
22 or by the manipulation of temporal presentation profiles.
23 24 25 Under these conditions, the RT has been shown to vary as a function of stimulus chromaticity.
18 25 Piéron, for example, found that RTs to red stimuli were shorter than those to green or blue stimuli,
19 whereas Nissen and Pokorny
22 have demonstrated that RTs to 570-nm stimuli are much longer than for other regions of the visible spectrum. The broad consensus that appears to emerge from these studies is that when the stimuli used to elicit RTs have poor chromatic selectivity and incorporate luminance changes that can be detected by achromatic mechanisms, then RTs are independent of stimulus chromaticity. If, however, stimuli possess good chromatic selectivity and minimize achromatic intrusions, then there is a strong dependence of RT on stimulus color.
22 24 This agreement may prove to be short lived. Recent work by Smithson and Mollon (Smithson HE, Mollon JD, ARVO Abstract 532, 2001) has shown that when luminance intrusion is controlled by masking, RTs to chromatic stimuli exhibit little change as a function of stimulus chromaticity.