The Bayesian brain

INT-01-W1 | Internal Architecture Series

Why our reality is a well-grounded hallucination

For as long as we have been trying to understand ourselves, we have relied on a specific, mechanical metaphor for the mind: the camera.

We tend to believe that our eyes are lenses, and our ears are microphones. We assume that we walk through the world, recording the objective reality around us, and that our brain simply processes this footage into a clear, high-definition movie called “Consciousness.” Following this logic, if your internal world feels chaotic—if you are plagued by anxiety, intrusive thoughts, or a sense of looming dread—you might assume your camera is broken. You might feel that your lens is cracked, distorting the world into something frightening that no one else seems to see.

Photo by Valeria Reverdo on Unsplash

But modern neuroscience offers us a shift in perspective that is as radical as it is relieving. The truth is that your brain is not a camera. It is not a passive recorder of reality. It is a tireless, aggressive prediction machine.

The brain does not see the world as it is; it sees the world as it expects it to be. This theory is known as Predictive Processing, or the “Bayesian Brain,” and it suggests that what we call “reality” is actually a controlled, top-down hallucination that our brain generates to save energy. Understanding this doesn’t just change how you view your biology; it fundamentally changes how you view your anxiety.

The dark room of the skull

To understand why the brain predicts rather than records, we have to look at its working conditions. Your brain is trapped in a dark, silent, bone-encased vault called the skull. It has no direct access to the outside world. It only has access to electrical scraps—scent molecules in the nose, photons hitting the retina, vibrations in the ear canal. This sensory data is often noisy, ambiguous, and slow. If the brain waited to fully process every single photon and sound wave before telling you what was happening, you would be paralyzed by the lag time. You wouldn’t be able to catch a ball, drive a car, or finish a sentence.

So, the brain cheats. It evolved to operate in reverse.

Instead of waiting for the world to tell it what is happening (bottom-up processing), the brain maintains a rich internal model of the world based on your past experiences. It projects these expectations outward, effectively guessing what is about to happen before it happens.

When you walk into your kitchen, you aren’t actually “seeing” the refrigerator in real-time. Your brain anticipates the refrigerator’s presence based on thousands of past mornings, and it hallucinates the image of the appliance to fill in the blind spots. It only checks the raw sensory data to make sure it hasn’t been moved. As long as the data matches the prediction, your brain hums along, satisfied. You are living in a simulation of your own making, constructed from the architecture of your past.

When the prediction fails

This system is brilliant for survival, but it is the root cause of what we call “anxiety.” In the language of neuroscience, anxiety is not an emotion; it is a prediction error.

A prediction error happens when the raw sensory data coming in from the world clashes with the model your brain projected. It is the jarring moment when you misstep on a staircase because you thought there was one more step. That sudden lurch in your stomach? That isn’t fear. That is your brain screaming, “Update the model! The map is wrong!”

For many of us, this mechanism has become hypersensitive. If you grew up in a chaotic environment, or if you have experienced significant trauma, your brain has curated a set of “priors”—deeply held expectations—that the world is volatile and dangerous. Because your brain’s primary job is to minimize surprise, it projects these danger-based predictions onto everything: an unread email, a neutral glance from a partner, a sudden phone call.

When you feel anxious, you aren’t necessarily reacting to reality. You are reacting to a prediction. Your heart is racing not because the tiger is in the room, but because your internal model has statistically calculated that a tiger should be in the room, and your body is preparing for the prophecy to come true.

The shift from defective to protective

There is immense compassion in this understanding. If we view the brain as a machine to be fixed, we treat anxiety as a malfunction. We try to numb it or shame ourselves into silence. But if we view the brain as a landscape of predictions, we can see anxiety for what it really is: a misunderstood attempt at safety.

Your brain is not trying to hurt you. It is trying to predict the future so it can protect you from it. The problem is simply that it is using outdated data to generate those predictions. It is running a “warzone” simulation in a “peace-time” environment.

This week, I invite you to step back and observe the machinery. When you feel that familiar tighten in your chest or the spiral of worry, try to pause. Instead of thinking, “I am broken,” try to ask, “What is my brain predicting right now?”

We are not victims of our reality; we are the architects of it. And the beautiful thing about an architecture built on prediction is that if we can change the data we feed the machine, we can eventually change the model itself. We can teach the brain to predict something new.

Next week, in INT-01-W2, we will explore the “Architecture of expectation” and why the brain clings so tightly to painful certainties rather than risking the unknown.

~Esteem Note Lab~