ABSTRACT
XIII. SPATIOCHROMATIC INTERACTIONS My early experiments with circular targets, like other contemporary studies of spatial vision, used only achromatic (white-light) stimuli, for two reasons: first, the color video displays that were available in those days were not really good enough to be used for controlled visual stimulation; and second, it seemed simpler to begin by omitting the complexities of color vision. But in due course, the first caveat lost its validity; and the second
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was actually somewhat illusory. A normal subject's color vision machinery is always functioning at photopic luminance levels, no matter what stimuli the experimenter chooses. (Note that "achromatic" describes a subjective appearance, not a wavelength distribution.)
The experiments reviewed below are not merely spatial vision studies or color vision studies, but inextricably, both. This double categorization may be frustrating if you think of the physical properties of the stimulus as separate and distinct dimensions, because the visual system doesn't keep them that way. Perhaps the interactions involved here will provide a bridge to some other chapters in this book.
