Tetrachromates

While ferreting around on the previous post I found reference to the fact that some women may actually be tetrachromates, seeing four basic colours rather than 3 for normal people or two and a bit like me.

There doesn’t seem to be an awful lot published on the issue, a few papers like this one but not a vast literature from what I can find.

The idea is interesting. There is even the suggestion that it could be expressed in the mothers of colour blind boys, which would have an impact I imagine about whether colourblindness genes were a net negative or positive selection criteria.

For years now, scientists have known that some fraction of women have four different cone photopigments in their retinas. The question still remains, however, whether any of these females have the neural circuitry that enables them to enjoy a different — surely richer — visual experience than the common run of humanity sees. “If we could identify these tetrachromats, it would speak directly to the ability of the brain to organize itself to take advantage of novel stimuli,” says Dr. Neitz. “It would make us a lot more optimistic about doing a gene therapy for color blindness.”

There have been very few attempts to find Madam Tetrachromat. The one that turned up Mrs. M in England, in 1993, was led by Gabriele Jordan, then at Cambridge University and now at the University of Newcastle. She tested the color perception of 14 women who each had at least one son with a specific type of color blindness. She looked at those women because genetics implies that the mothers of color-blind boys may have genetic peculiarities of their own. Among that somewhat peculiar group of women, one could expect to find the odd tetrachromat.

It’s almost as if the supersense these women enjoy comes at the expense of the men in their families. “I’m just sorry I’ve robbed my son of one of his color waves,” Mrs. M says.
….
Would there be any practical advantages to tetrachromacy? Dr. Jordan notes that a mother could more easily spot when her children were pale or flushed, and therefore ill. Mrs. M reports that she has always been able to match even subtle colors from memory — buying a bag, for example, to match shoes she hasn’t laid eyes on for months. And computers, color monitors, and the Internet raise a whole raft of possibilities. Just as someone with normal three-color vision surfs rings around a dichromat on the Internet, a tetrachromat, looking at a special computer screen based on four primary colors rather than the standard three, could theoretically dump data into her head faster than the rest of us.

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5 Responses to Tetrachromates

  1. Sacha says:

    I read that birds are tetrachromates, and can see into the ultraviolet where we can’t – maybe in the current scientific american?

  2. Steve says:

    Interesting Sacha. I think this stuff is interesting because its very easy to assume that everything sees the same, when in fact its pretty clear that there is a fairly wide divergence even within our own species. People think that the colour blind just don’t see “all the colours” but all colours isn’t an absolute its a function of our eye’s make up. Tetrachromates would have a similar opinion of normal vision etc.

    Perhaps thinking of this in terms of a fourier series is helpful. We take some complicated incoming EM wave. Normal visions represent this by the superpostion of three diferenent frequency and intensity waves, dichromates, do it more poorly with only two, and tetrachromates do it better with four chanels to mix.

    None of them though are getting the full picture.

  3. Sacha says:

    Yes it’s interesting, isn’t it – a good reminder that there is literally more than one view of (material) things – ok, I know it’s cliche, but it’s a lesson our non-scientific friends can perhaps be more aware of – that you have to be always aware of other possibilities when looking at an issue – it’s good to question your assumptions.

    Now, I have to work on my paper!

  4. Sacha says:

    Or the potential of other possibilities.

  5. Rick Auterson says:

    Tetras dump data from the internet into their head faster? Rubbish.

    Tetras would be at a definite disadvantage looking at an RGB screen. It would contain only 1% of the colors they see in the world, washed out, perhaps random colors.

    Tetras don’t just see more shades of colors, they see more colors. Yellow for example is a mental construct, it’s what our mid says to us when the red and green cones get fired. There is no yellow wavelength.

    What color does a tetra see when their red and Other (Orange maybe) cone gets fired? Our distant ancestors had four cones, our recent ancestors only two, yellow and blue., At some point the yellow cone split into red and green. But at a basic chemical and neurological level we were once able to process 4 color channels. Birds and insects do it, why not us.

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