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Hallucinations Your Brain Create, Called Reality

Updated: Jul 28, 2023

Have you ever seen a friend’s face in a crowd, but when you looked again, you realized it was a different person? Have you ever felt your cell phone vibrate in your pocket when it didn’t? Have you ever had a song playing in your head that you couldn’t get rid of?

Well, you probably answer at least one of them as yes. Which brings us to the common point of what neuroscientists like to say: “Your day-to-day experience is a carefully controlled hallucination, constrained by the world and your body but ultimately constructed by your brain.”

This is not like a hallucination that make you feel like you are crazy. This is just the normal way of our brains’ working. This is the moment your brain gives meaning to your sense data.

Why am I telling this?

Cause I’m fascinated by neuroscience, I’ve always been. Hence, I’m also reading some books related to it and one of my favourite one is “Seven and a Half Lessons About the Brain” by Lisa Feldman Barrett who is known as among the top 1% most cited scientists in the world for her revolutionary research in psychology and neuroscience.

In this post, I will try to fascinate you too by telling how our ever-predicting brains construct our reality by predictions.


Let’s start with an example.

Dr. Barrett mentions that she receives an e-mail from a soldier, served in the Rhodesian army in southern Africa in the 1970s to hunt down guerrilla fighters. One day, when he was practicing exercises with his small squad of soldiers in the forest, he detected a movement. His heart started to pound and he saw a long line of guerrilla fighters in camouflage and carrying machine guns. He instinctively raised his rifle and targeted at the leader. Then suddenly his buddy behind him approached and said “Don’t shoot him, he is just a boy.” He slowly lowered his rifle and astonished by what he saw: A boy, perhaps ten years old, leading a long line of cows, with a simple herding stick which he supposed as a rifle.

After this experience, the man struggled to understand how he had managed to mis-see and he was about to shoot a ten-years old boy and doubted about something is wrong with his brain.

At the times when the soldier was actually fighting in the forest, whenever he sensed the sights, sounds and smells of guerrillas, his brain constructed some sensations in his body, such as pounding heart. When the soldier saw the shepherd boy, his brain asked: “Based on what I know about this war, and given that I’m deep in the woods with my comrades, gripping a rifle, heart pounding and there are moving figures ahead, then what am I likely to see next?” – Guerrilla fighters.

And this is called; prediction.

Keep that in mind. Now, let’s go one step further to dig into what does this prediction mean.



There is a good metaphor of Dr. Barrett about predictions. She says, predictions are just your brain having a conversation with itself. Meaning that; a bunch of neurons make their best guess about what will happen in the immediate future based on whatever combination of past and present that your brain is currently conjuring.

About this whole constructive process happens predictively, Dr. Barrett gives an example to bring this prediction concept to life. Think of the last time you were thirsty and drank a glass of water. Within seconds, when you finish the glass, you feel immediately less thirsty. This may seem ordinary at first, but scientifically water takes about twenty minutes to reach your bloodstream. Water can’t possibly relieve your thirst in a few seconds. Then what relieves? Prediction. Our brains are predicting the experience of drinking water and preparing our bodies to drink and swallow, it simultaneously anticipates the sensory concequences of gulping water and causing us to feel less thirsty before your brain learns from the body about your increased hydration.

The predictive process is not so linear though. In the soldier example: Is that sound he heard was an enemy fighter, or due to the wind in the forest or something else?

Before answering that, a reminder from the book: Our brains construct what we feel inside our body. Then it also adds information from our past experiences to guess what those sensations inside our body mean. (Hold that part). Ultimately, prediction happens. As I said earlier, our brain’s predictive process is not quite linear though. Dr. Barrett tells that our brain has several ways to deal with a given situation, and it creates a flurry of predictions and estimates probabilities for each one.

At this point, if we go back to the questions above, they are basically probabilities of the given situation. In each moment, some prediction is winner and Dr. Barrett states that often, it is the prediction that best matches the incoming sense data and the winning prediction becomes our action and our sensory experience.

Remember that our brain is not only reliant on the sense data we are receiving constantly from the world but also uses the information coming from our past experiences. Which is an additional source of information, called: Memory. Think about the things that have happened to you personally, things you have learned from your friends, school, books – in a nutshell, all your life experiences. Our brain assembles all those bits into memories to infer the meaning of the sense data and guess what to do about it.

But remember the part you hold just a moment ago: Our past experiences include not only what happened in the world around us, but also what happened inside our body.

Before going back to the soldier example, I’ll touch upon one more thing on what’s happening inside the body to hopefully make all the information more sense at your end.


Our brain’s representation of sensations from our body is called: Interoception. This means it is the process where our brain produces our body’s inner sensations, such as a gurgling stomach, a tightness in your chest, and even the beating of your heart; basically, the construction of all our inner sensations.


Now let’s go back to the part the soldier saw a shepherd boy with a bunch of cows and supposed them as guerilla fighters.

When it was real wartime and the soldier faced guerrilla fighters, the situation matched his brain’s prediction. From his brain's perspective, the real fighters confirmed the prediction, because his brain already constructed the sights, sounds, and smells of fighters, and prepared his body to act, in that case, prepared him to the rifle and shoot.

It became his experience, his reality.

“When your predicting brain is right, it creates your reality. When it’s wrong, it still creates your reality, and hopefully, it learns from its mistakes.”

In this case, the soldier’s prediction was wrong. The past experience stored in his brain – aka the information inside his brain – triumphed over the data from the outside world at that very moment. Fortunately, the soldier’s friend tapped him on the shoulder, prompting him to look again and by this way, allowed the soldier’s brain to launch new predictions for the given situation.

Dr. Barrett says most of the time when we look at cows, we see cows.

But remember my questions at the beginning:

Have you ever seen a friend’s face in a crowd, but when you looked again, you realized it was a different person?

Probably yes, and the reason of it is the same with why the soldier’s brain predicted guerrilla fighters when he faced a shepherd boy with a herding staff and a bunch of cattle in reality.

The soldier’s brain constructed a sensation (pounding heart) by using his past experience related to guerrilla fighters and by receiving some sense data (the sounds and the movements in the forest) and his head produced everything he sees based on these sensations and his past experience.


If I summarize what I have talked about so far:

  • Our day-to-day experience is constructed by our brain.

  • This constructive process happens predictively. Which means our brain begins to sense the moment-to-moment changes in the world around us before all the light waves, chemicals, and other sense data hit our brain.

  • Our brains construct what we feel inside our bodies. Then it also adds information from our past experiences to guess what those sensations inside our body mean. Ultimately prediction happens.

  • Memory is a critical ingredient in this construction process as includes our past experiences.

  • In conclusion, our brain recreates the past from memory by asking itself; “The last time I encountered a similar situation, when my body was in a similar state and was preparing this particular action, what did I see next? What did I feel next?”

  • (Just like in the soldier example. His brain was able to create feelings of terror from a thundering heart based on his past experience in the war.)

  • The answer becomes our experience.

All of these lead us to the point that we are actually living in a world of our own construction.

Isn’t it amazing when you look at your whole life from this perspective?


Now I’m finishing, for real.

Two key things to remember and as future reference as well:

  1. The key thing is all those predictions that initiate our actions don’t appear out of nowhere. For instance, if you hadn’t chomped on your nails as a kid, you probably wouldn’t bite them now.

  2. Your brain’s predictions are not always correct. It means we have some control over our brain’s predictions in the future.

I’m intending to make a little series on this topic. We will see how it goes. In the next chapter of the series, we will dig into those two points above. Cause why not? ☺️

Stay tuned!

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Last month, I tried to explain the process by which our daily experiences are constructed by our brains based on a neuroscience book and an example I read. You can refresh your memory here. At the end


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