What do illusions do

You remember The Dress , yes? In , a bad cellphone photo of a dress in a UK store divided people across the internet. Some see this dress as blue and black; others see it as white and gold. Is it in bright daylight?

Or under an indoor light bulb? By unconsciously filtering out the color of light we think is falling on an object, we come to a judgment about its color. Wallisch believes people who see this image differently are using different filtering schemes.

Most interestingly, he suggests that life experience leads you to see the dress one way or the other. His study of 13, people in an online survey found a correlation that at first seems odd. The time you naturally like to go to sleep and wake up — called a chronotype — was correlated with dress perception.

Night owls, or people who like to go to bed really late and wake up later in the morning, are more likely to see the dress as black and blue.

Larks, a. Wallisch believes the correlation is rooted in the life experience of being either a lark or a night owl. Larks, he hypothesizes, spend more time in daylight than night owls. So when confronted with an ill - lit image like the dress, they are more likely to assume it is being bathed in bright sunlight, which has a lot of blue in it, Wallisch points out.

As a result, their brains filter it out. Night owls, he thinks, are more likely to assume the dress is under artificial lighting, and filtering that out makes the dress appear black and blue. But not all of it. But we have no way of knowing how our experiences guide our perception. Wallisch says the disagreements around The Dress, as well as other viral illusions like Yanny and Laurel , arise because our brains are filling in the uncertainties of these stimuli with different prior experiences.

We bring our life histories to these small perceptions. In this illusion, the Pac-Man-like shapes give the impression of a triangle in our minds. We only need the suggestion of one — implied via the corners — to fill in the rest of the picture with our minds.

It may be that a lifetime of looking at triangles is what makes the rest of us see one so plainly in this image. He had to build them from scratch. What is the same is that I am still guessing. The horizontal lines are actually parallel, and not at all slanted.

Look at the distance between them at the start and end of each row if you don't believe it. Wonderful version of the cafe wall illusion, by Victoria Skye. Some of these examples may seem frivolous. Why does it matter that one person sees a dress as black and blue and another sees it as white and gold? It matters because scientists believe the same basic processes underlie many of our more complicated perceptions and thoughts.

In the past, researchers have found that even slight rewards can change the way people perceive objects. Take this classic image used in psychological studies.

What do you see? In one experiment, the participants played a game wherein they had to keep track of animals they saw on screen. In the end, a high score meant getting a candy treat desirable! The very last thing the participants saw was the above image. In a more complex example , Balcetis has found that when she tells study participants to pay attention to either an officer or a civilian in a video of a police altercation, it can change their perception of what happened depending on their prior experience with law enforcement and the person in the video with whom they more closely identified.

But you can encourage people to listen to other perspectives and be curious about the veracity of their own. The neuroscientists I spoke to said the big principles that underlie how our brains process what we see also underlie most of our thinking. The ambiguity is going to be resolved one way or another, and sometimes in a way that does not match reality. Political scientists and psychologists have long documented how political partisans perceive the facts of current events differently depending on their political beliefs.

In a way, you can think of bias as a social illusion. Studies find that many people perceive black men to be bigger and, therefore, potentially more threatening than they actually are , or generally associate darker skin tones and certain facial features with criminality.

Cops can confuse people removing wallets from their pockets with people reaching for guns, often with tragic consequences. Our brains work hard to bend reality to meet our prior experiences, our emotions, and our discomfort with uncertainty. This happens with vision. But it also happens with more complicated processes, like thinking about politics, the pandemic , or the reality of climate change.

Wallisch has come up with a name for phenomena like The Dress that generate divergent perceptions based on our personal characteristics. And because we have different priors, that leads to disagreement about the image or event in question. Wallisch sees it everywhere in society.

Stephen L. Follow Stephen L. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter. The spinning dancer illusion shows an ambiguous silhouette that appears to abruptly change direction.

Learn more about how this illusion works. In this image, you see the silhouette of a woman spinning. Which direction is she turning? You may be surprised to learn that it is possible to see her spinning both clockwise and counterclockwise. While it may be very difficult, you can probably get her to switch directions spontaneously. Try looking at the figure and then blink; she may appear to change directions immediately after you blink. Another strategy is to focus on a specific part of the figure.

In reality, the spinning dancer illusion is related to a bistable perception in which an ambiguous 2-dimensional figure can be seen from two different perspectives. Because there is no third dimension, our brains try to construct space around the figure. People typically see the clockwise variation, which research suggests can be attributed to a tendency to assume a viewpoint from above the figure as well as a tendency to perceive movements of the right as opposed to the left foot.

The oblique lines look as if they are crooked and will diverge. In reality, all of the oblique lines are parallel. Much like the Muller-Lyer and Herring illusions, this optical illusion demonstrates how the background of an image can distort the appearance of straight lines. First, the angle of the short lines compared to the longer lines creates an impression of depth. One of the lines appears to be nearer to us; the other farther away. Another possible explanation is that the brain attempts to increase the angles between the long and short lines.

This results in distortion as the brain tries to bend the lines away and towards each other. Interestingly, if the color of the lines is switched to green and the background to red, the effect completely disappears as long as the two colors are of equal brightness.

In the Ames room illusion, two people standing in a room appear to be of dramatically different sizes, even though they are the same size. The image above was captured by a visitor to the "Ames room" in the Villette science museum in Paris, France and uploaded to Flickr, a photo-sharing website. In the room, the individual on the left appears to be very tall, while the person on the right looks very small. In reality, both people are of approximately the same height and size.

The effect works by utilizing a distorted room to create the illusion of a dramatic disparity in size. While the room appears square-shaped from the viewer's perspective, it is actually has a trapezoidal shape. The woman on the right hand side of the image above is actually standing in a corner that is much further away than the woman on the left.

The illusion leads the viewer to believe that the two individuals are standing in the same depth of field when in reality the subject is standing much closer. The effect can be observed in a number of films, including The Lord of the Rings trilogy.

Note the early scenes in The Fellowship of the Ring where the effect is prominently used to make Gandalf appear larger than the hobbits. You can see more examples of Ames rooms in these YouTube videos. In the Ponzo illusion, two identically-sized lines appear to be different sizes when placed over parallel lines that seem to converge as they recede into the distance.

In the image above illustrating the Ponzo illusion, the two yellow lines are the exact same size. Because they are placed over parallel lines that seem to converge in the distance, the top yellow line actually appears to be longer than the bottom one. The Ponzo illusion was first demonstrated in by an Italian psychologist named Mario Ponzo. The reason the top horizontal line looks longer is that we interpret the scene using a linear perspective.

Since the vertical parallel lines seem to grow closer as they move further away, we interpret the top line as being further off in the distance. An object in the distance would need to be longer in order for it to appear the same size as a near object, so the top "far" line is seen as being longer than the bottom "near" line, even though they are the same size.

The Kanizsa Triangle is an optical illusion in which a triangle is perceived even though it is not actually there. The Kanizsa Triangle illusion was first described in by an Italian psychologist named Gaetano Kanizsa. In the illusion, a white equilateral triangle can be seen in the image even though there is not actually a triangle there.