Now that the garbage fire is in our rearview mirror in 2020, social media is making a return to serious discussions that really matter. Like how many colors a thing has. Again.
Earlier this month, a classic optical illusion was posted on Twitter asking “How many colors do you see?” The poster saw three.
How many colors do you see ???? I see 3 pic.twitter.com/IgEHtyzebZ
– jade⁷🍓 (still ♡) (@ 0UTR0EG0) February 4, 2021
Others responded with numbers like higher than 17. And tens of thousands of comments followed in a heated debate over what the ‘true’ figure should be.
We here at ScienceAlert do not have a strong opinion on how many different bands are in the picture (it’s 11, right?). But we can help provide insight into what is likely to happen.
Although it is difficult to say with certainty, the phenomenon at work is probably the result of an effect that was first described by the Austrian physicist Ernst Mach a century and a half ago. speed of sound.
Only in this case did Mach’s interest have less to do with speed and more to do with sight. While working as a professor of mathematics and physics at the University of Graz in the 1860s, he developed a deep interest in optics and acoustics.
In 1865 he became interested in an illusion similar to the one we are all currently amazed at – similar colors of slightly contrasting shades become easily distinguishable when they touch each other, but more difficult to distinguish from each other.
Mach’s understanding was that something strange was going on in the eyeball, specifically in the light – sensitive tissue that makes up the retina. Later, these shadow stripes would be known as Mach Bands in his honor.
Strikingly, his speculations were pretty scary. Research with better technology than Mach ever hoped to gain access to has confirmed the mechanics behind this strange trick of the eye as a retinal behavior called lateral inhibition.
This is the 101: your retina is a bit like the screen in the cinema and captures the light projected by the pupil. This screen is covered with receptors, some of which respond more powerfully under bright light and send a shower of signals to the brain.
If we think that two cells send two very similar signals to the brain, we can assume that they have the same color. Our brains like shortcuts, and in a busy world it really does not have time to tear hair.
But nature has developed a clever trick to help our brains more easily distinguish patterns between similar shades. When an individual photosensitive cell sends a signal, it tells its immediate neighbors to shake.
This competition makes little difference between groups of cells that all shout and push as loud as each other.
But when a quieter group of cells, responding to a darker shadow, sits right next to hard cells, this inhibitory effect on cells on the border forces them to respond in a unique way, effectively increasing the difference between the shades.
(ScienceAlert)
The diagram above can help you understand what is happening. Bright light causes receptors to intrigue the corresponding nerve cell more. At the same time, every light-sensitive cell suppresses the nerves of its neighbors.
The result is nerves on the border between different shades that send signals that amplify the difference and provide a clear boundary signal that your brain can pick up.
This ability plays a role in a variety of optical illusions, including a crazy ‘dazzling grid’ of points you can never really focus on.
While lateral inhibition explains why our eyes can better distinguish similar shades when they are next to each other, it does not completely explain why some of us can not tells the difference between colors with barely contrasting brightness, as in this illusion.
Inhibitory influences in our cells may be something we all experience to varying degrees, but they are also probably not the only factor that tells our brain how to interpret an image. Much of it will be unique to our eyes, brains, computer screens and surrounding environments.
Surrounding light sources, the differences in the brightness of our screens and monitors, and even the exact cellular composition of our retina will all differ. Our brains will also add a level of correction in their own unique way, depending on their experience and hard wiring.
Since there are so many variables, it is to be expected that we will not all agree on exactly where one pink tint stops and the next begins.
These are all fun and games on Twitter, but knowing more about how our retinas improve the differences in the shades that fall on them can help us find ways to improve our vision.
Remember that we are not experts in optics here at ScienceAlert. It’s all speculation of one science writer who happens to have a deep love for the psychology of illusions.
But we know that beyond the question of how many colors (or, more accurately, colors, shades, shades, and shades) are in the rectangle, there is a fascinating biology going on that can tell us a lot about what we have in common.