Color Blindness

With red/green color blindness, this image:

would look like this:
or this:

or this:

and the interesting thing is that we can't really say which of those it would look like: how would you design a test to tell whether someone saw red as green or whether they saw green as red?
Actually, most people who are color blind are only partially color blind, so they see it more like this:

and if you are partially color blind, this is what the top image looks like to us full trichromats:


tpmotd said…
Great post, Doug!
D said…
I'm not exactly satisfied. When I ask myself, "what would a blind person see?" and follow the same methodology I used here, I end up with a flat black, or white, or grey screen. But that's not right-- they don't have a visual field at all.

On the other hand, maybe they do have a visual field and its being filled in by their imaginations. (i.e. mind's eye.)
mike said…
Well, it probably depends a lot on whether they've been blind from birth. Late-blind users of vOICe report actually seeing images though the data is entirely audio. It would be really cool to compare brain scans of early- and late-blind people using vOICe to tell how much the visual cortex was involved in each case.
mike said…
Also, there are the FMRI studies that can read out of the visual cortex what a person is actually seeing. So if you can figure out what the difference between red and green is *in the brain*, you could then look at a colorblind's brain and tell what they were perceiving.

I think this is what they expect over at Blue Brain, but in more detail.

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