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Let's all think colorful thoughts...



I suspect that a lot of you have been predicting that I would write
something to the list about the thread on color vision.  Since I like
seeing predictions come true, I'm doing that now...

First off, Joseph Daniel <jdaniel@aristotle.net> wrote:

> Let's not confuse coorblindness for lack of color vision. If I
> remember correctly, most mammals can see color, they are just
> colorblind (meaning, they don't distinguish certain colors) as well
> as primates or reptiles.  Doing a red-green test on a dog for
> instance would yield no difference,

The spirit of Joe's comment is correct, but a wee bit of clarification
is in order.  The "red-green test" to which Joe refers would have to
be carefully controlled.  Red and green are separate qualities to us
and not to dogs; that's true.  However, the test necessary to show
that "red things" look just like "green things" to dogs.  Just as a
ripe banana or lemon will look more yellow to you than one that is
less ripe, a red apple will look more "dog-yellow" to a dog than will
a green one, and it may be more or less bright.  Just because the dog
can't discriminate two objects the same way you do doesn't mean it
can't discriminate them at all.

Also, due to the vagaries of the way color vision systems are
constructed, even animals (e.g., dogs) with color vision that is not
as well-developed as ours can make some spectral discriminations
better than we can.

Shifting gears,  Emily Tremain <etremain@gac.edu> wrote:

] But then you have those cuttlefish who are supposedly color-blind
] yet turn every color of the rainbow...

I saw that article in this month's "Natural History" too, and I'm more
than a little skeptical.  A search of the Science Citation Index from
1970 to now pulled up exactly zero articles when I searched on
"cuttlefish and color".  A similar search of a biological sciences
data base pulled up four articles, one of which had some very slight
relevance.  I know of some older papers indicating that color vision
in Octopus isn't that great, but I have more than reasonable doubts
that cuttlefish could match their backgrounds as well as they do
without having a sensory system that was capable of providing the
information necessary for making the matches...  I *really* want to
study cuttlefish right now.  Perhaps some time in the next few years I
will have a chance.  If anybody knows of any relevant papers, please
pass them along since I'm going to start building up a bibliography
for future use.

Lastly, "Matthew Bonnan" <mbonnan@hotmail.com> (who should know better
:-) wrote:

) If we use a phylogenetic bracket hypothesis, then, we might be able
) to say this, if birds and crocodilians represent the living outgroups
) to dinosaurs:

First off, this topic has come up a few times on this list (looks like
it's been almost a year -- May 1999) since the last time.  People
might want to look through the archives before continuing this thread.

Second, I've heard a rumor that a paper describing what we can "know"
about color vision in dinosaurs will be out soon.  So I must invoke
one of Holtz' rules and ask that you be patient...

-- 
Mickey Rowe     (rowe@psych.ucsb.edu)