THE NEURAL BASIS OF COLOR 
CONSTANCY
Since type 1 cells in the 
lateral geniculate body seem 
not to be geared to make color-
spatial comparisons, we 
probably have to look beyond 
the retina and geniculate. To 
test the idea that such 
computations might go on in 
the cortex, Land's group and 
Margaret Livingstone and I 
examined a man who had had 
his corpus callosum severed 
surgically to treat epilepsy. 
Spatial-color interactions did 
not take place across the 
visual-field midline, that is, 
the color of a spot just to the 
left of the point at which the 
subject was looking was not 
affected by drastic changes in 
the colors in the right visual 
field, whereas normal subjects 
observed marked differences 
with such changes. This 
suggests that the retina by 
itself cannot mediate the color-
spatial interactions. Although 
no one had seriously claimed 
that it could, the question 
continued to be debated, and it 
was satisfying to have some 
experimental evidence. The 
experimental results are 
consistent with our failure to 
find retinal ganglion cells that 
could plausibly be involved in 
color-spatial interactions.

    The goldfish, which makes 
spatial comparisons very much 
like ours, has virtually no 
cerebral cortex. Perhaps the 
fish, unlike us, does make such 
computations with its retina. 
Nigel Daws' discovery in 1968 of 
double opponent cells in the 
fish retina seems to bear this 
out. In the monkey, as I 
describe in the next section, 
we find such cells in the cortex 
but not in the lateral 
geniculate or the retina.