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In the end, the vision specialists figured out what was going on. They weren’t computer screens or eyes. These were mental calculations that the brain makes when we see. Some people subconsciously assumed that the dress was under direct light and mentally subtracted yellow from the image, so they saw blue and black stripes. Others saw that he was in the shade, where bluish light predominated. Their brain mentally subtracted the blue from the image and came up with a white and gold dress.

Not only does thinking filter reality; it constructs it by inferring the outside world from the ambiguous input. V To be youAnil Seth, a neuroscientist at the University of Sussex, shares his explanation of how “the inner universe of subjective experience is related to and can be explained by biological and physical processes in the brain and bodies.” He claims that “experience To be you, or to be me, arise from how the brain predicts and controls the internal state of the body. ”

Forecasting has become fashionable in academia in recent years. Seth and philosopher Andy Clark, his Sussex colleague, call the predictions made by the brain “controlled hallucinations.” The idea is that the brain is always building models of the world to explain and predict incoming information; it updates these models when the predictions and experiences we get from our sensory inputs diverge.

“Chairs are not red,” Seth writes, “just as they are not ugly, old-fashioned, or avant-garde … When I look at a red chair, the redness I experience depends on both the properties of the chair and the properties. my brain. It matches the content of a set of perceptual predictions about how a particular type of surface reflects light. ”

Seth is not particularly interested in redness or even color in general. Rather, his broader assertion is that the same process applies to all perception: “The wholeness of perceptual experience is a neural fantasy that remains attached to the world through the continuous creation and processing of better assumptions of perception, controlled hallucinations. You could even say that we all hallucinate all the time. It’s just that when we agree on our hallucinations, this is what we call reality. “

Cognitive scientists often rely on atypical examples to understand what’s really going on. Seth walks the reader through an amusing list of optical illusions and demonstrations, some of which are familiar and others less so. Squares of the same shade appear to be different; spirals printed on paper appear to spontaneously rotate; an incomprehensible image turns out to be a woman kissing a horse; face appears in the bathroom sink. By recreating the psychedelic powers of the mind in silicon, the AI-powered VR rig he and his colleagues created creates a Hunter Thompson-style menagerie of animal parts emerging piecemeal from other objects on a plaza on the University of Sussex’s campus. This series of examples, Seth says, “throws away the seductive but useless intuition that consciousness is one thing, one big scary mystery in search of one big scary solution.” Seth’s point of view can be frustrating for those who choose to believe that things are what they seem: “The experience of free will is perception. The passage of time is perception. ”

Seth takes a relatively solid position when he describes how the brain forms experiences, what philosophers call “easy” problems of consciousness. They are easy only in comparison with the “difficult” problem: why subjective experience exists at all as a feature of the Universe. Here he goes awkwardly, introducing the “real” problem, which is to “explain, predict, and control the phenomenological properties of conscious experience.” It is not clear how the real problem differs from the simple ones, but, according to him, solving it will somehow help us solve a complex problem. That would be a neat trick.

Where Seth mostly talks about the experiences of people with typical brains fighting atypical stimuli, in Coming to your sensesSusan Barry, Emeritus Professor of Neuroscience at Mount Holyoke College, tells the stories of two people who acquired new senses later than usual. Liam McCoy, who had been nearly blind since infancy, was able to see almost clearly after a series of surgeries when he was 15 years old. Zohra Damji was deaf until she received a cochlear implant at the unusually late age of 12. As Barry explains, Damji’s surgeon “told her aunt that if he knew the length and degree of Zohra’s deafness, he would not have performed the operation. … Barry’s compassionate, detailed and observant narration is based on her own experiences:

At the age of forty-eight, my vision improved dramatically, and this change has repeatedly brought me moments of childish joy. Cross-eyed from early childhood, I saw the world mainly with one eye. Then, in the middle of my life, I learned through a vision therapy program to use my eyes together. With every glance, everything I saw took on a new look. I could see the volume and three-dimensional shape of the empty space between things. The branches of the trees reached out to me; lamps floated. A visit to the grocery department of a supermarket with all its colors and three-dimensional shapes could throw me into a kind of ecstasy.

Barry was overjoyed at her new ability, which she describes as “seeing in a new way.” She tries her best to point out how different this is from seeing it for the first time. A person who has grown up with eyesight can grasp the scene at a glance. “But where we perceive a three-dimensional landscape full of objects and people, the newly sighted adult sees a jumble of lines and colored spots appearing on the same flat plane.” As McCoy described to Barry his experience of climbing and descending stairs: