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<div class="moz-cite-prefix">On 03/05/2013 19:07, Dan wrote:<br>
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<div style="font-family: arial, helvetica, sans-serif;
font-size: 12pt; "><span>Since Eugen mention tetrachromacy --
almost typed "tetrachromancy" :) -- did anyone see that
report on mantis shrimp:</span></div>
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<div style="background-color: transparent; "><span><a class="moz-txt-link-freetext" href="http://www.sciencenews.org/view/generic/id/343056/description/Mantis_shrimp_flub_color_vision_test">http://www.sciencenews.org/view/generic/id/343056/description/Mantis_shrimp_flub_color_vision_test</a><br>
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<div style="color: rgb(0, 0, 0); font-size: 16px; font-family:
arial, helvetica, sans-serif; background-color: transparent;
font-style: normal; "><span>Strange that they have some of the
hardware, but don't seem to be using it in the expected way.</span></div>
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It is hard to test animals on vision. In Sönke Johnsen's excellent
"The Optics of Life" he points out that in many domains we are very
bad at figuring out what makes sense to animals, and this makes our
experiments less able to tell us much. Mantis shrimp are *weird*.
(they show up in almost every chapter as an extreme case)<br>
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<div style="color: rgb(0, 0, 0); font-size: 16px; font-family:
arial, helvetica, sans-serif; background-color: transparent;
font-style: normal; "><span> I also wonder, given that color
opponent theory, if there's any processing going on at
higher levels. (I might be wrong here, gotten mixed up on
what I've read about this, but I presume opponents happen at
a higher level of processing than color discrimination. Am I
wrong? Maybe I also missed something...)</span></div>
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It is likely the retinal bipolar cells that create the opponent
signals, which are then transmitted via the optic nerve to the
brain. So the color discrimination actually works on opponent colors
(differences between red-green and yellow-blue, plus brightness)
rather than the "raw" red, green and blue signals.<br>
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<pre class="moz-signature" cols="72">--
Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University </pre>
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