Biology Reference
In-Depth Information
700
600
500
400
400
500
Wavelength (nm)
600
700
Fig. 12.2 Scotopic contrast hues (○) together with additive opponent
hues (● ). Abscissa represent wavelength of pre-stimulation while the
ordinate represents wavelength of scotopic contrast hues. The field
subtended 1 × 2° and was applied 6° temporally to the fovea.
12.4 Scotopic hues explained
The conclusion opposed the basic assumptions of the Young-Helmholtz
colour theory that the different receptor types functioned independ-
ently of each other, and that each receptor type mediated one colour
quality only (see Helmholtz,
1896
). The trichromatic colour theory,
therefore, had little to offer as a theoretical basis of the scotopic
contrast colours.
The question, then, arose of whether the conclusions could
be explained more easily within the framework of Hering's (
1878
)
opponent colour theory.
Hering had realized that colour vision must involve opponent
colour processing somewhere in the visual pathway, but his phenom-
enological approach did not allow any conclusion as to the site of the
antagonistic interactions. Three quarters of a century later, however,
