"New" colours possible?

C.J.L. Wolf C.J.L.Wolf at ncl.ac.uk
Thu Nov 1 10:26:03 EST 2001


On Thu, 1 Nov 2001, Richard Norman wrote:

> On Thu, 1 Nov 2001 09:44:18 -0000, "Tris" <null at 127.0.0.1> wrote:
> >It's true, but apparently colour-blindness is good for predatory animals.
> >Could this be why men are more likely to be colour-blind than women?
> >
Is this the male or female perspective?!

> >Colourful camouflage is less confusing to the colour-blind - so now
> >camouflage patterns must be tested by people with 'normal' vision, *and*
> >people who are colour-blind.
> >
I read a paper about this by morgan a while back - WOS is down at the
moment, so forgive me if I don't pass on the ref for the moment. I heard
that american servicemen who were colourblind found jungle warfare easier
because they could see motion against the foliage more easily - but I
could never find a reference at the time and wondered if the story was
apocryphal?

> The usual argument is not that color-blindness is "good" for predatory
> animals.  It goes that color-vision is coadapted with brightly colored
> fruits and vegetables 

Vegetables? There are other arguments, for example that because of
chromatic abberation (the inability of the human eye to focus blue and red
parts of the spectrum at the same time, if they're coming from the same
surface) a monochromatic visual system can have better acuity than one
that has to see colour. Plus it could be a darn sight simpler.

> (at least for terrestrial animals -- insect,
> birds, and a few orders of mammals).  Sexual selection and
> intra-specific communication accounts for other cases.
> 
> Colorful camouflage is not less confusing.  Animals who use camouflage
> defense and have the ability to change their color must not only match
> their background with shading and pattern, but also in color.  That
> makes the problem more difficult, not easier.
> 

There are some rather neat ishihara plates that only people with colour
vision deficiencies can see. There are rather subtle dichromat
(yellow-blue) patterns hidden amongst strong red-green patterns. Colour
normals can only attend to the stronger pattern.

KW




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