We think our brain is some kind of computer. A computer that processes information coming from the senses – what we see, hear, taste, feel, etc. – so that we can respond to the world. But that idea is incorrect. You couldn’t survive with a brain that would work like that (input – processing – output).
The time it takes for the brain to consciously perceive something is too long to be able to respond in time. For example, it takes about a fifth of a second to “see” something. When you play tennis and your opponent hits the ball, the signals that hit your retina take about 200 milliseconds to reach your conscious brain. Only then do you see the ball leave. But in those same 200 milliseconds the ball has already passed the net for top tennis players. With less powerful hits, the ball is already quite close to the center of the tennis court. So the moment you see the ball leave, it is actually already halfway. And by the time you’ve seen that ball go over the net, the ball has already passed you. If a brain worked like a computer and thus had to receive and then process information from the senses, not only would we not be able to play tennis, we would not be able to do many other things: keeping balls out of the goal in football, being able to answer a question immediately, jumping away in time for an unwary cyclist and much more. We would often be too late. And that’s not good if you want to survive on this planet.
The brain has found a solution for that problem. It doesn’t wait until it gets input from the senses. It predicts that input. Tennis players do not follow the ball with their eyes, but predict the course that the tennis ball will follow. Perception is therefore not a passive process in which the brain receives information from the senses. It is an active process in which the brain predicts what will happen. Seeing the tennis ball does not start in the eyes, but within the brain: with an expectation.
The first time you play tennis, your brain doesn’t really know where tennis balls go. If you have never played tennis before, you have little experience on which to rely to predict where the ball will go. Your brain will therefore makes several wrong guesses. The ball lands in a different place than where you expected and predicted it. That is a prediction error. A prediction error occurs when there is a difference between what your brain predicted and what it eventually (after a fifth of a second) gets to see. Those prediction errors are what the human brain processes. The brain does not process stimuli, but the difference between the stimulus it expected and the stimulus it receives.
Our brain does not like prediction errors. Our brain therefore wants as few prediction errors as possible. You will never be able to win a game of tennis if you keep guessing where the ball will land. The brain now has two options for reducing prediction errors.
The first is to update the predictions. That is “learning”. By playing a lot of tennis, your brain gets better and better at predicting where the ball will land. The number of prediction errors decreases, which increases the pleasure of playing tennis.
A second way to reduce prediction errors is to do something, to intervene in the world. You change the game of tennis in such a way that the ball always ends up where you expect it to be. For example, you can make the tennis court so small that your opponent has no choice but to let the ball land on your racket. It is doubtful whether there is still a lot of fun to be had, but at least you no longer have any prediction errors.
That is the main task of our brain: prediction error minimization through learning and acting. Both the predictions as the prediction error minimization are highly context sensitive.
And this is where the autistic brain reacts differently. The autistic brain tends to predict and treat prediction errors in an absolute rather than relative way.
The picture below shows the difference between an autistic and a non-autistic brain using tennis as an example. Want to hear the explanation? Register for the webinar on autism and the predictive mind on April 28th!
The above text is part of my new book “Autisme en het voorspellende brein” (‘Autism and the predictive mind’).