WEBVTT - What Colors Are Impossible? 0:00:01.840 --> 0:00:07.640 Welcome to Brainstuff, a production of iHeartRadio, Hey, brain Stuff, 0:00:07.680 --> 0:00:13.000 Laura vogelbaumb here. Even at full function, our eyes don't 0:00:13.039 --> 0:00:16.079 provide us with a complete picture of the world around us. 0:00:16.720 --> 0:00:20.040 There are plenty of things we can't see under normal circumstances, 0:00:20.520 --> 0:00:24.800 like ultraviolet wavelengths or impossible colors like stiggy and blue. 0:00:25.680 --> 0:00:28.280 Sticky and blue if you're unfamiliar, is what's called a 0:00:28.360 --> 0:00:32.880 chimerical color. It's an after image. Specifically, it's the color 0:00:32.920 --> 0:00:36.000 you perceive when you stare at a bright yellow circle, 0:00:36.159 --> 0:00:39.440 say for several seconds, and then look at a black square, 0:00:40.640 --> 0:00:43.519 you'll see an after image of a deep blue circle, 0:00:43.920 --> 0:00:47.080 a blue that's just as dark as the black against 0:00:47.159 --> 0:00:50.600 the black square. The color is named after the underworld's 0:00:50.680 --> 0:00:54.800 river sticks. Of course, a blue that's as dark as 0:00:54.880 --> 0:00:59.720 black is impossible, but our weird brains nevertheless perceive it 0:01:00.920 --> 0:01:04.200 if it helps. There's actually no such thing as blue 0:01:04.319 --> 0:01:09.520 to begin with, or red or green or fusia. These 0:01:09.600 --> 0:01:14.360 are just words we have for particular sensory experiences. Color 0:01:14.680 --> 0:01:20.319 exists purely in our minds. A banana, for example, is 0:01:20.400 --> 0:01:24.360 not inherently yellow. To prove it is, stumble to your 0:01:24.440 --> 0:01:26.120 kitchen in the middle of the night and hold a 0:01:26.120 --> 0:01:28.920 banana in front of your face. What color is it then? 0:01:29.680 --> 0:01:33.679 Kind of a muddy grayish black, probably definitely not bright yellow. 0:01:34.760 --> 0:01:38.360 And that's because colors are not emitted from most objects. 0:01:38.520 --> 0:01:42.839 They are reflected. A banana is yellow because when visible 0:01:42.920 --> 0:01:46.000 light hits it, the wavelengths that we call yellow are 0:01:46.040 --> 0:01:50.440 what bounce back. We've talked about light and color before. 0:01:50.960 --> 0:01:53.520 A white light from the sun or a normal light 0:01:53.560 --> 0:01:57.440 bulb is composed of wavelengths spanning the entire visible spectrum. 0:01:58.080 --> 0:02:02.120 You know your basic ROYGBIV, going from the longest wavelengths 0:02:02.200 --> 0:02:06.240 to the shortest. That's red, orange, yellow, green, blue, indigo, 0:02:06.280 --> 0:02:10.760 and violet. But when white light shines on a banana peel, 0:02:11.160 --> 0:02:16.440 something frankly incredible happens. There's a natural pigment in the 0:02:16.480 --> 0:02:21.040 peel called xanthophyl that's chemically programmed to absorb certain wavelengths 0:02:21.040 --> 0:02:25.320 of light and reflect others. The dominant wavelength reflected by 0:02:25.400 --> 0:02:29.800 xanthophyl is yellow, but the yellow of that banana still 0:02:29.840 --> 0:02:33.839 doesn't exist as such. It only starts to exist when 0:02:33.840 --> 0:02:37.640 the reflected light from that peel is detected by millions 0:02:37.680 --> 0:02:42.440 of color sensing cells in your retinas called cones. Most 0:02:42.520 --> 0:02:46.280 humans have three types of cone cells, referred to as red, green, 0:02:46.360 --> 0:02:50.200 and blue cones, or more accurately as long, medium, and 0:02:50.320 --> 0:02:53.880 short cones, because each are more sensitive to wavelengths of 0:02:53.960 --> 0:02:58.120 light in those ranges. The cones send a multitude of 0:02:58.120 --> 0:03:02.800 electrical impulses to the brain that data is processed. Each 0:03:02.880 --> 0:03:06.079 cone can process one hundred or more different shades of color, 0:03:06.560 --> 0:03:09.720 giving your average human a range of a million to 0:03:09.720 --> 0:03:15.040 ten million perceivable colors. Some evolutionary biologists think that this 0:03:15.200 --> 0:03:19.359 trichromatic color vision evolved in primates to help us spot 0:03:19.440 --> 0:03:24.760 colorful berries amongst foliage. But we know that other animals 0:03:24.840 --> 0:03:28.760 perceive color differently because they evolved to have different numbers 0:03:28.880 --> 0:03:32.919 or types of cones. Dogs, for example, have just two 0:03:32.960 --> 0:03:36.640 types of cones, blue and yellow. They don't really perceive 0:03:36.720 --> 0:03:42.360 reds and greens. Most birds have four types of cones, red, green, blue, 0:03:42.400 --> 0:03:46.520 and ultraviolet, meaning that they can see colors we can't. 0:03:47.080 --> 0:03:50.000 Honeybees can see into the infrared part of the spectrum. 0:03:51.840 --> 0:03:56.080 Now ultraviolet and infrared light exist, we know they do. 0:03:56.200 --> 0:03:58.840 We can observe them in other ways, and we know 0:03:58.920 --> 0:04:02.320 that what we call yellow light exists. It's the part 0:04:02.320 --> 0:04:05.840 of the electromagnetic spectrum with wavelengths around five hundred and 0:04:05.880 --> 0:04:10.680 seventy two five hundred and eighty nanometers or thereabouts. But 0:04:11.440 --> 0:04:15.600 other colors that we perceive technically don't exist, like sticky 0:04:15.640 --> 0:04:21.000 and blue, or think about magenta. Magenta is what we 0:04:21.080 --> 0:04:24.640 see when our brains process a combination of red and 0:04:24.720 --> 0:04:28.719 blue light. But red and blue are on opposite ends 0:04:28.720 --> 0:04:32.120 of the visible spectrum. There is no wavelength for magenta. 0:04:33.279 --> 0:04:35.600 On the flip side of the coin, people with red 0:04:35.600 --> 0:04:38.680 green color deficiency might not be able to cite the 0:04:38.680 --> 0:04:43.600 difference between red and green apples. For them and for 0:04:43.680 --> 0:04:49.000 the best dog in your life, those colors don't exist. 0:04:49.520 --> 0:04:53.360 The moral of this color story is this, without our 0:04:53.480 --> 0:04:58.000 visual system and without our brains, no color really exists. 0:04:58.480 --> 0:05:01.719 It's all in the mind of the ball, which is 0:05:01.839 --> 0:05:06.560 enough to make you say dude, And it leads to 0:05:06.640 --> 0:05:10.920 a fascinating question. Are there colors within the visible spectrum 0:05:11.040 --> 0:05:15.799 that our cones and brains can't see? The so called 0:05:15.920 --> 0:05:21.440 impossible colors or forbidden colors break the biological rules of perception. 0:05:23.880 --> 0:05:27.520 We're going to get more into impossible colors, but first 0:05:27.560 --> 0:05:29.480 we're going to get into a quick break for a 0:05:29.520 --> 0:05:38.279 word from our sponsors, and we're back. Thank you sponsors. Okay, 0:05:38.440 --> 0:05:41.400 to talk about this, let's start by digging deeper into 0:05:41.400 --> 0:05:45.680 the science of color perception. Each of your eyes contains 0:05:45.800 --> 0:05:49.960 roughly six million cones concentrated in the center of the retina. 0:05:50.120 --> 0:05:53.400 These cones come in those three different varieties types that 0:05:53.440 --> 0:05:57.200 pick up on short, medium, or long wavelengths of visible light. 0:05:58.360 --> 0:06:01.760 When a cone receives a strong sign in its wavelength zone, 0:06:01.960 --> 0:06:05.800 it sends electrical impulses to the brain. The brain's jobs 0:06:05.839 --> 0:06:08.719 to combine the millions of electrical signals from each cone 0:06:09.000 --> 0:06:12.560 to recreate a composite image of the color that you're 0:06:12.560 --> 0:06:15.960 looking at. The brain, of course, is not a computer, 0:06:16.480 --> 0:06:20.599 but rather has a complex lump of highly specialized cells 0:06:20.920 --> 0:06:25.440 called visual cortex that's responsible for processing the electrical signals 0:06:25.480 --> 0:06:29.560 from the cones. We're still learning how these cells work 0:06:29.880 --> 0:06:32.760 and work together and with other regions of the brain 0:06:33.279 --> 0:06:38.440 to process input from the eyes. But basically the color 0:06:38.480 --> 0:06:42.680 related cells are called opponent neurons, and they traditionally have 0:06:42.760 --> 0:06:46.760 been separated into two basic types, red green opponent neurons 0:06:46.960 --> 0:06:52.080 and blue yellow opponent neurons. They're called opponents because they 0:06:52.120 --> 0:06:55.840 function in a binary way. The red green opponent neuron 0:06:55.920 --> 0:07:00.000 can signal either green or red, but not both simultaneou, 0:07:01.640 --> 0:07:05.080 and the blue yellow opponent neuron can signal either blue 0:07:05.279 --> 0:07:09.960 or yellow. I feel obligated to say here that recent 0:07:10.000 --> 0:07:13.960 research has indicated that this explanation is actually a culturally 0:07:14.080 --> 0:07:18.600 convenient oversimplification of what seems to be a three ish 0:07:18.640 --> 0:07:24.160 step brain process that more precisely involves lavender lime opponent 0:07:24.200 --> 0:07:29.200 neurons and salmon teele opponent neurons of five varying opponentcies 0:07:29.680 --> 0:07:34.360 that can combine to red versus green, and blue versus yellow. 0:07:34.760 --> 0:07:37.880 But since I'm not a neuroscientist, oh, let's stick with 0:07:37.960 --> 0:07:44.920 the convenient oversimplification for today. Okay, So, opponent neurons how 0:07:44.960 --> 0:07:48.360 they basically work is this. When you look at a 0:07:48.400 --> 0:07:51.679 pure yellow image, the yellow portion of the blue yellow 0:07:51.680 --> 0:07:55.600 opponent neuron is excited and the blue portion is inhibited. 0:07:56.680 --> 0:07:59.320 Switch to a pure blue image, and the blue portion 0:07:59.440 --> 0:08:02.360 of the opponent neuron is excited while the yellow is inhibited. 0:08:03.480 --> 0:08:06.600 And now imagine trying to see an image that's equally 0:08:06.800 --> 0:08:10.800 blue and yellow at the same time. The opponent neurons 0:08:10.960 --> 0:08:16.679 can't be both excited and inhibited simultaneously. That's why bluish 0:08:16.760 --> 0:08:20.360 yellow is an impossible color. The same is true for 0:08:20.480 --> 0:08:24.600 reddish green. You might be saying, I know what yellow 0:08:24.600 --> 0:08:27.440 and blue look like together. It's green and red and 0:08:27.480 --> 0:08:30.440 green make a kind of muddy brown. But that's the 0:08:30.480 --> 0:08:34.240 result of mixing two colors together, not of a single 0:08:34.280 --> 0:08:39.560 pigment that's equally blue yellow or red green. All the 0:08:39.559 --> 0:08:42.440 way back in eighteen oh one, long before scientists knew 0:08:42.440 --> 0:08:47.000 about cones and neurons, English physician Thomas Young theorized that 0:08:47.040 --> 0:08:51.000 the human eye has three types of color receptors, blue, green, 0:08:51.080 --> 0:08:56.240 and red. Young's trichromatic color theory was proven correctsh in 0:08:56.280 --> 0:08:59.640 the nineteen sixties, when cone cells, named for their shape, 0:08:59.720 --> 0:09:03.679 were to discovered to have special sensitivity to about those wavelengths. 0:09:04.880 --> 0:09:07.720 The opponent color theory of perception has been around since 0:09:07.760 --> 0:09:12.679 the eighteen seventies, when German physiologist Edvald Herring first postulated 0:09:12.679 --> 0:09:15.839 that our vision was ruled by opponent colors across from 0:09:15.840 --> 0:09:18.240 each other on the color wheel, with the corset being 0:09:18.440 --> 0:09:22.800 red versus green and blue versus yellow. This theory is 0:09:23.040 --> 0:09:27.160 simple and intuitive enough that it's still repeated in physiology textbooks, 0:09:27.520 --> 0:09:30.560 but in the past five to ten years, neural imaging 0:09:30.679 --> 0:09:33.120 has shown that what's going on in our brains is 0:09:33.240 --> 0:09:38.400 more complicated. Still, it's functional enough to roll with for today. 0:09:39.520 --> 0:09:44.680 So taken together, trichromatic theory and opponent theory argue that 0:09:44.840 --> 0:09:48.280 it is impossible for the human eye and mind to 0:09:48.320 --> 0:09:55.400 perceive certain colors described as red, green, or blue yellow. However, 0:09:55.720 --> 0:09:58.840 as Luigi wisely told us in the nineteen ninety three 0:09:58.920 --> 0:10:04.599 Super Mario Brothers Life live action film, nothing's impossible, improbable, unlikely, 0:10:05.080 --> 0:10:11.160 but never impossible. In that spirit, in the early nineteen eighties, 0:10:11.400 --> 0:10:15.760 visual scientists hewet Crane and Thomas Piantinada designed an experiment 0:10:15.840 --> 0:10:19.479 with the goal of tricking the brain into seeing impossible colors. 0:10:20.679 --> 0:10:23.800 In their experiment, subjects were instructed to stare at an 0:10:23.840 --> 0:10:27.080 image of a vertical red stripe adjacent to a vertical 0:10:27.200 --> 0:10:31.160 green stripe. The subject's heads were stabilized with a chin rest, 0:10:31.320 --> 0:10:34.720 and their eye movements were tracked by a camera. With 0:10:34.920 --> 0:10:37.760 every tiny twitch of a subject's eyes, the redd and 0:10:37.800 --> 0:10:41.400 green image was automatically adjusted so that the subject's gaze 0:10:41.440 --> 0:10:46.240 remained fixed on the opposing colors. It turned out that 0:10:46.320 --> 0:10:49.960 if people stared at adjacent opposing colors for long enough, 0:10:50.360 --> 0:10:54.840 the border between them would dissolve and new impossible colors 0:10:54.920 --> 0:10:59.440 would emerge. The resulting colors were so new that subjects 0:10:59.480 --> 0:11:03.640 had a hard time describing them. By stabilizing the image 0:11:03.640 --> 0:11:07.559 to track eye movements, the researchers theorized that different areas 0:11:07.600 --> 0:11:10.880 of the eye were being continuously bathed in different wavelengths 0:11:10.880 --> 0:11:14.720 of light, causing some opponent neurons to get excited and 0:11:14.760 --> 0:11:19.280 others to be inhibited at the same time. But after 0:11:19.400 --> 0:11:23.040 several other researchers failed to achieve the same dramatic results, 0:11:23.520 --> 0:11:28.800 this experiment was dismissed as a parlor trick. Subjects, instead 0:11:28.800 --> 0:11:31.960 of seeing brand new hues of greenish red or bluish yellow, 0:11:32.320 --> 0:11:36.840 usually described the blended color as mud brown. Others would 0:11:36.880 --> 0:11:40.640 see fields of green with pixelated red dots scattered across it. 0:11:41.600 --> 0:11:47.040 Impossible colors became a scientific joke. But then in twenty ten, 0:11:47.480 --> 0:11:52.040 biophysicists Vincent Bellick and Brian Zoe published results that they 0:11:52.120 --> 0:11:56.559 believed explained why Crane and Piontinita had succeeded where others 0:11:56.559 --> 0:12:01.600 had failed. They identified the combination of eye tracking and 0:12:01.960 --> 0:12:05.960 luminance or brightness as being key to tricking the brain 0:12:06.240 --> 0:12:10.800 into seeing impossible colors. They ran their own experiments in 0:12:10.800 --> 0:12:13.400 which subjects were again strapped to a chin rest and 0:12:13.480 --> 0:12:18.360 monitored by the latest retinal tracking technology, With the images 0:12:18.440 --> 0:12:22.520 stabilized to these subject's eye movements. The researchers played with 0:12:22.559 --> 0:12:26.760 the luminance of the two opposing color stripes. When there 0:12:26.840 --> 0:12:29.840 was a difference in brightness, the subject's experienced to the 0:12:29.920 --> 0:12:34.160 pixelated colors reported in earlier experiments. But when the two 0:12:34.160 --> 0:12:37.840 colors were exactly the same brightness, then six out of 0:12:37.880 --> 0:12:43.320 seven observers saw impossible colors. Even better, two of them 0:12:43.360 --> 0:12:45.880 could see the new colors in their minds for hours 0:12:45.920 --> 0:12:50.200 after the experiment was over. While few of us have 0:12:50.320 --> 0:12:54.120 a retinal stabilizer in the basement, there are some simpler 0:12:54.160 --> 0:12:58.520 exercises that can temporarily trick the brain into seeing the forbidden. 0:13:00.200 --> 0:13:03.160 Direct is to stare at an image of two opposing 0:13:03.240 --> 0:13:06.280 color squares side by side, each with a white plus 0:13:06.320 --> 0:13:09.400 sign in the middle. You can find examples of this online. 0:13:10.679 --> 0:13:14.160 What you do is relax and cross your eyes until 0:13:14.200 --> 0:13:18.200 the two plus signs merge into one. I tried this 0:13:18.960 --> 0:13:22.160 the blue, yellow one was weird, and the red green 0:13:22.240 --> 0:13:27.000 one made me laughably uncomfortable. Sort of makes you wonder 0:13:27.040 --> 0:13:29.800 what else is out there that we can't see yet. 0:13:34.640 --> 0:13:37.679 Today's episode is based on the article how impossible colors 0:13:37.840 --> 0:13:40.520 like Stiggy and Blue work on how stuffworks dot Com, 0:13:40.520 --> 0:13:43.760 written by Dave Ruse. Brain Stuff is production of iHeartRadio 0:13:43.840 --> 0:13:46.240 in partnership with how stuffworks dot Com and is produced 0:13:46.240 --> 0:13:49.559 by Tyler Klang. Four more podcasts from my heart Radio. 0:13:49.800 --> 0:13:53.280 Visit the iHeartRadio app, Apple Podcasts, or wherever you listen 0:13:53.360 --> 0:13:54.400 to your favorite shows