In this second animation, the object on the right really is moving diagonally. Trace it with your finger again. With fMRI neuroimaging , which allows researchers to map brain activity, Cavanagh and his team could ask the question: If we perceive each animation similarly, what in our brains makes that happen?
One possibility is that the illusion is generated in the visual cortex. Located at the back of your head, this is the part of your brain that directly processes the information coming from your eyes. The experiment included only nine participants but collected a lot of data on each of them.
Each participant completed the experiment and was run through the brain scan 10 times. That visual system in the back of the brain? Each animation produces a different pattern of activation in the visual cortex. Then why do we perceive them as being the same? That is: The front of the brain thinks both animations are traveling in a diagonal direction.
To be sure: Vision is a vastly complex system involving around 30 areas of the brain. You can see it for yourself. The lesson: The stories our brains tell us about reality are extremely compelling, even when they are wrong. Why are we seeing a story about the world — a story — and not the real deal?
Think about what it takes to perceive something move, like the objects in the above animations. From there, the signal travels forward through our brains, constructing what we see and creating our perception of it. This process just takes time. So the brain predicts the path of motion before it happens.
It tells us a story about where the object is heading, and this story becomes our reality. It happens all the time. See for yourself. The red dot is moving across the screen, and the green dot flashes exactly when the red dot and green dot are in perfect vertical alignment. The red dot always seems a little bit farther ahead. This is our brain predicting the path of its motion, telling us a story about where it ought to be and not where it is. It helps us overcome these delays and see things The actual sensory information, he explains, just serves as error correction.
Our brains like to predict as much as possible, then use our senses to course-correct when the predictions go wrong.
This is true not only for our perception of motion but also for so much of our conscious experience. The brain tells us a story about the motion of objects. It also tells us stories about more complicated aspects of our visual world, like color. For some meta-insight, look at the illusion below from Japanese psychologist and artist Akiyoshi Kitaoka. You can observe your own brain, in real time, change its guess about the color of the moving square.
Keep in mind that the physical color of the square is not changing. You might look at this illusion and feel like your brain is broken I did when I first saw it. It is not. A moving square appears to change in color, though the color is constant.
Color is an inference we make, and it serves a purpose to make meaningful decisions about objects in the world. Red may not appear red when bathed in blue light. Our brains try to account for this. When we think an object is being bathed in blue light, we can filter out that blue light intuitively. Sometimes those guesses are wrong, and sometimes we make different assumptions from others. Neuroscientists have some intriguing new insights into why our perceptions can diverge from one another.
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. Sometimes those guesses are wrong, and sometimes we make different assumptions from others. Neuroscientists have some intriguing new insights into why our perceptions can diverge from one another.
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. For instance, a magician often directs the audience's gaze to one hand while he does something with the other. But Rosenblum doesn't see the human tendency to fall for such misdirection as evidence that all of reality exists only in our minds. As members of society, people create a form of collective reality. For example, money, in reality, consists of pieces of paper, yet those papers represent something much more valuable.
The pieces of paper have the power of life and death, Freeman says — but they wouldn't be worth anything if people didn't believe in their power. Another fiction humans collectively engage in is optimism. Neuroscientist Tali Sharot of University College London studies "the optimism bias": people's tendency to generally overestimate the likelihood of positive events in their lives and underestimate the likelihood of negative ones.
In the show, Sharot does an experiment in which she puts a man in a brain scanner, and asks him to rate the likelihood that negative events, such as lung cancer, will happen to him. Then, he is given the true likelihood. When the actual risks differ from the man's estimates, his frontal lobes light up. But the brain area does a better job of reacting to the discrepancy when the reality is more positive than what he guessed, Sharot said.
This shows how humans are somewhat hardwired to be optimistic. That may be because optimism "tends to have a lot of positive outcomes," Sharot told LiveScience.
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