Why your brain forces your senses to perceive reality to fit preconceived ideas

Seeing is believing, right? Well … perhaps not. In the early 1700s, the philosopher Bishop Berkeley pointed out that we never experience the outside world directly – we only experience what our sense perceptions tell us about that world. We assume that our sense perceptions realistically portray the outside world and provide us with accurate information about it. So if we see a cat, we think that the cat exists pretty much as we see it. While this is a good – and necessary – assumption for going about daily life, Daniel Yon, an experimental psychologist and cognitive neuroscientist at the University of London in the UK, says that is not how the brain works. In his book A Trick of the Mind (2025), he says that what we actually see and hear is the result of a two-way process between the information already logged in our brains and the new information supplied by our senses. The brain tries hard to fit our sensory experiences into a model of what it thinks they should be, and it can even change them to fit its preconceived ideas of what we should be seeing or hearing. “The brain is fundamentally like a scientist,” Yon says during a lecture event presented by the British science magazine New Scientist. “It’s in the business of making its own theories and predictions to make sense of the world. Those models then become the lens and filter through which everything else is seen.” Yon uses the cover of A Trick of the Mind to illustrate his point. It depicts a large red apple on a blue background – or does it? Although many people see the apple as red, it is completely grey. Grey apples do not exist, so our brain automatically adjusts the grey sensory perception of the apple so it looks red. “What you are seeing is what your brain has come up with to make sense of what’s in front of you,” Yon says. “In the theory it has built up, an apple is red. And it’s that theory, rather than reality, that you subjectively experience.” In short, the representation of reality that your brain provides after processing your sensory perceptions may not always match reality, he says. It can get things wrong as well as right. What is more, this applies to all three “realities” that humans inhabit: the material world of things, our own mental world, and the more abstract reality of concepts and ideas. The material world is where we trust our brain’s depiction of reality the most. “When we think about sensory organs like our eyes and ears, we think they work like cameras or microphones, recording the world around us,” Yon says. “But the latest psychology and neuroscience is suggesting that our senses are not really like these instruments at all.” Our eyes do not really photograph the world, he says. It is more likely that they collect and send information to the brain, which then adapts that information to fit with its preconceived ideas of what we are “seeing”. “As our brains are relying on these theories and hypotheses to perceive the world, we might end up not always being in touch with reality as it is. We might be living in a world which is as we expect it to be, instead,” Yon says. It is possible that this could be a contributing factor to conditions such as schizophrenia. This would make schizophrenics more like extreme versions of people who are not considered mentally ill: “All of us see the world through a filter of our own brain’s design,” Yon notes. In terms of our mental reality, this is especially relevant to the way we try to understand other people. We observe how people act and look, then fit them into our brain’s preconceived models, Yon says. But that usually leads to misconceptions and misunderstandings. “We don’t just confuse the world, we confuse other people, with these models of perception,” he says. “We can be prone to misunderstanding others when we encounter those who don’t fit with the assumptions and prior beliefs that our mind has already laid down.” Trying to understand other people is a bit like trying to understand what life looks like on other planets, he notes. “When scientists look for life on a distant planet, they don’t get the chance to visit and see what that planet is actually like,” he says. “What scientists do is come up with a model of what life is like on Earth – a model of what signs of life look like in our own backyard. Then we look for these signs at a distance.” When we are trying to figure out other people, we also look for external signs. “Although we have everyday phrases like ‘getting inside someone else’s head’, in reality, we can never visit someone’s mind and see what their life is like. Instead, we observe them, trying to find signs in their behaviour,” Yon says. We can learn a lot through observing other people’s body language, and have evolved to be good at that, Yon admits. The problem is that our brain’s models of what body language means are inefficient. Body language is affected by factors including age and culture. For instance, young people often perceive older people to be angry when they are not – their faces are simply less expressive due to the mechanics of ageing. That is why it is easy for us to misjudge people, Yon says. So if our brains are giving us a vision of the world that does not truly represent reality, should we try to change its processes? Philosophers, religions and authors have often encouraged us to try to “open the doors of perception” and experience reality as it is, through meditation, religious experiences or psychedelic drugs. But that is not actually a good idea, cautions Yon. The brain has evolved this process to supply us with information about reality in a way that we can use it, he says. Remove the brain’s theories and filters, and we would be swamped with chaos and unable to go about our daily lives. “In The Matrix, there is a scene in the beginning in which the protagonist, Neo, experiences all sorts of strange things that make him doubt that reality works the way he thinks it does,” Yon says. “Morpheus offers him a couple of pills. If he takes the blue pill, he will go back to his comfortable delusion about how the world works. If he takes the red pill, he will have his preconceptions and biases removed and see reality as it really is.” In The Matrix, Neo takes the red pill, as otherwise there would not be a film. But in reality, Yon says that we should take the blue pill and return to our “delusion” – which is exactly what he himself would do, he adds. Reality, some theoretical physicists are starting to think, is actually similar to one big, mad acid trip. Our brains just let a sliver of reality in so that we can function. “If you took the red pill, the world would be infinite – ambiguous, chaotic and uncertain,” Yon says. “Without those theories the brain makes for you, the world just wouldn’t make sense. Taking away those theories won’t actually make you see more clearly.” Like what you read? Follow SCMP Lifestyle on Facebook, X and Instagram. You can also sign up for our eNewsletter here.

Why your brain forces your senses to perceive reality to fit preconceived ideas

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}The representation of reality your brain provides after processing sensory perceptions may not match the real thing, a neuroscientist says

The representation of reality your brain provides after processing sensory perceptions may not match the real thing, a neuroscientist says