Abstract
The well-known difference in appearance for monochromatic stimuli presented in the fovea compared to the peripheral retina is at least in part due to the presence of rod receptors. Whether the effects of rods enter into perception abruptly or gradually across time has not yet been investigated. Here observers described the appearance of 8 monochromatic stimuli ranging from 480 to 620 nm using the “4+1” color naming procedure. Stimuli presented at 10° temporal eccentricity were equated to 20 photopic tds. Following a broadband (5500K) bleaching stimulus, stimuli were presented every 4 min for 28 min, allowing data collection at and between times associated with the cone and rod plateaus of the dark-adaptation function. Results indicate that as time following the bleach increased, the stimuli progressively decreased in saturation. In general, hue percentages ascribed to green, yellow, and red decreased until about 16 minutes, after which they stabilized. In contrast, the percentage ascribed to blue, and for some observers, short-wavelength red, systematically increased with time following the bleach. The above procedure was repeated for the 480, 500, 520 and 540 nm stimuli equated to 100 scotopic tds. Overall, the percentages of red, blue and saturation did not differ between the photopic and scotopic conditions, but the percentages of yellow and green did differ. Thus, the effect of rods across time appears abruptly and data from the peripheral retina may differ if stimuli are equated photopically versus scotopically.