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More critically, the mantis shrimp doesn’t have opponency. In humans—-and most other animals—-the visual system represents color[0] using a relative system: is
by mattkrause 8y ago
More critically, the mantis shrimp doesn’t have opponency.
In humans—-and most other animals—-the visual system represents color[0] using a relative system: is something redder than it is green? Bluer than it is yellow? To create this, neurons receive excitatory input from (e.g.) a red cone and inhibitory input from nearby green cones. This representation makes sense, given the cones’ spectral sensitivity, but it also makes some colors “impossible”. Since each color is essentially a point along these two axes, something can’t be blue and yellow at the same time, reddish green, or even some shades of “hyper-green”[1,2].
The mantis shrimp, near as we can tell, doesn’t have this sort of representation. The anatomical pathways don’t seem to be there, and some behavioral work with trained(!) mantis shrimp also suggests that they have independent color channels, and, as a result, their color sensitivity is actually not amazing. Interestingly, they may do something to “fake” color opponency: different receptor types are in different parts of the eye, and the shrimp ‘drags’ its eye across the scene to produce a sort of temporal context.
That’s more than you probably wanted to know but...shrimp are neat.
[0] To a first approximation, anyway.
[1] There is a place called Reddish Green, which I assume is not invisible, but I’ve never been to Stockport, England.
[2] More seriously, there are some tricks you can play to (briefly) perceive some of these impossible colors. The general approach is that you stare at something of one color, then quickly switch to looking at something of the opponent color. This “fatigues” (adapts) cells that signal the first color, so they provide less inhibitory input in response to the second color.
- hobs 8y agoA great talk about treating lazy eye with VR that discusses creating impossible colors by providing different inputs to different eyes (also just generally cool, discusses multiple methods to have the brain reset the disabling of one eye) - https://www.youtube.com/watch?v=_r1Tj5-F4XI&t=2875s https://www.youtube.com/watch?v=_r1Tj5-F4XI&t=2875s
- andyjohnson0 8y agoI lived in Reddish for a while, about 25 years ago. I sometimes used to take a book and sit under the trees on Reddish Green to read. The grass was definitely just regular, visible, non-impossible-coloured grass :) https://www.google.com/maps/@53.4386822,-2.1639276,3a,62.9y,277.15h,86.87t/data=!3m6!1e1!3m4!1sV1OSAm5j5cjEurZXkszkvQ!2e0!7i13312!8i6656 https://www.google.com/maps/@53.4386822,-2.1639276,3a,62.9y,...
- IIAOPSW 8y agoBut how do I know you're possible-coloured?
- kakarot 8y agoHere is a blog post which covers some impossible colors and provides a few techniques to "see" them. [0] Of course reddish green and blueish yellow don't have any easy visualization techniques. My personal favorite impossible color is Stygian Blue. Something is so energizing about seeing a color you know shouldn't exist. [0] http://www.luniere.com/2014/03/01/hyperbolic-orange-and-the-river-to-hell/ http://www.luniere.com/2014/03/01/hyperbolic-orange-and-the-...
- Forbo 8y agoI think you forgot your link.
- Chris_Chambers 8y agoHe just colored the link in Stygian Blue.
- kakarot 8y agoHasn't been a great start to the day. Thank you!
- FPGAhacker 8y agoI see reddish green all the time, although it could be greenish red. Just as often it’s brown. I’m red-green colorblind.
- tachyonbeam 8y agoFun aside: your mention of the mantis shrimp led me to google image search them, and it turns out that they are very colorful creatures (http://caradonnajournal.com/wp-content/uploads/2018/04/Peacock-Mantis_01.jpg http://caradonnajournal.com/wp-content/uploads/2018/04/Peaco...). Their special visual system and bright colors are likely a result of sexual selection.
- feedbeef 8y agoMantis shrimp pack a really strong punch too. Truly fascinating creatures. https://www.ted.com/talks/sheila_patek_clocks_the_fastest_animals https://www.ted.com/talks/sheila_patek_clocks_the_fastest_an...
- mattkrause 8y agoYup! They're one of the few animals that can see circularly-polarized light, and the quarter-wave retarders in their eyes are really damn good. As of a few years ago, they had a much wider wavelength range (400-700 nm) than the best man-made ones, which were only achromatic over ~100 nm.