What is color?

If you’ve ever wondered if colors were really out there in nature or if they only existed in our minds then listen to last month’s Radiolab episode on Colors, “where Jad and Robert tear the rainbow to pieces.” Given its audio format, one of the standouts in the episode is the sonic interpretation of how a rainbow might appear differently to a dog, a human, and a mantis shrimp.

Comparison of the visible color spectrum of humans vs dogs.

Dogs, like most mammals, are dichromats–their eyes only have 2 types of photoreceptors: blue and yellow. This puts dog color vision on par with humans that are red-green colorblind. Humans, on the other hand, are trichromats, having a third photoreceptor for red in addition to blue and yellow.

Putting all of us to shame, the mantis shrimp has a whopping total of 16 types of photoreceptors (hexadecachromat anyone?), allowing them to see polarized light and into the UV spectrum (and perhaps appreciate each other’s pretty colors!)

Now imagine being a dog and not being able to appreciate this…OR imagine being a mantis shrimp and what a total mindbomb this would be:

The rest of the episode explores genetic engineering experiments that confer trichromacy to monkeys, the hunt for the fabled human “tetrachromat,” the mysteriously violent history of gamboge (a brilliant, yellow dye), and why blue is the last color to be attributed a word in nearly every culture.

Vertical stripes: The new black

Black clothing has a slimming effect due to an optical effect known as the “irradiation illusion, in which a black rectangle surrounded by white looks smaller than the same rectangle in white surrounded by black.”

The central squares are the same size, despite appearances given by the “irradiation illusion”

Another optical illusion suggests that horizontal stripes would also have a slimming effect. But amateur scientist and participant in Radio 4’s “So You Want to Be a Scientist?” Val Waltham disagrees. She put this effect to the test in 3-D by dressing models in outfits consisting of either vertical stripes, horizontal stripes, or plain black. Based on surveys she found that, “vertical stripes make people look taller, while horizontal hoops make them look wide – but plain black was the most slimming of all.”

Mental images

Close your eyes. Now imagine that you’re at the beach. Picture the sun, the sand, and the waves. Ever wonder how your mind creates these mental images? Neuroscientists at UTHealth are studying the neural mechanisms that allow us to form these images with the ultimate goal of designing a visual prosthetic to help the blind “see.”

Your eyes can play tricks on you

Have time to kill? Try this mysterious eye experiment.


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