September 24, 2023

I want to bust a myth about brains. All brains, not just autistic brains – but I don’t think you can fully understand autism without understanding this first.

Most people think that a brain works like a computer: First you get input from your senses, then you process it, then you act on it.

But actually, before any of that, your brain makes a prediction.

There’s something it expects to see, or hear, or feel. Maybe a floor strewn with toys, if that’s common in your house – or an empty floor if not.

Your brain may be right, or it may be wrong. So it still needs sensory input to confirm or deny the prediction.

That’s the first step of processing – confirming or denying a prediction.

If what you see matches what you expected, then your brain has less work to do. It can carry on exactly as planned, with nothing more to process.

If what you see doesn’t match what you expected, then your brain is surprised. You then have to wonder: Does this new information matter?

That’s the second step of processing – deciding which surprises matter.

A surprise matters if it changes your plans. If you almost trip over a toy on the floor, then you pick it up or walk around it.

A surprise also matters if it changes your model of reality. If you see a toy suspended in midair, then you look for a string – or question gravity.

Most surprises don’t matter, so you don’t need to spend brainpower on them. There’s no cause for concern if a toy moved across the room since you last saw it – it might not even feel like a surprise.

But context matters. If no one else was around to move the toy, then a simple change in its position would be a startling mystery.

To recap, perception doesn’t begin in your senses – that’s a myth. Perception really begins in your brain, as a prediction about what your senses will soon experience.

That’s all true in autistic brains, too. But studies show that we differ in these ways:

1. Our sensory predictions are often incorrect. This is because the lessons we draw from past experiences tend to be too precise – they only feel relevant if the situation is nearly identical.

(This doesn’t apply to our conscious, logical predictions – only our subconscious, automatic ones.)

2. Our awareness of context is often incomplete. This is because we tend to focus more on individual details than on how those details fit into the big picture.

3. Since all brains need context to decide if a prediction error matters – and autistic brains face more errors with less context – our brains tend to conclude that IT ALL MATTERS.

Which is fine, if we’ve got enough time to think everything through and decide what to do about it. The problem is, we rarely do have enough time – especially in conversations.

Neurotypical brains work faster because they use predictions to save time. No brain can react immediately to sensory input, but it’s a lot faster if a prediction is ready and turns out to be correct.

Autistic brains also make sensory predictions, but it doesn’t save time – it just creates more errors to process. So over time, we begin to rely less on our predictions.

Instead, we see with fresh eyes, taking in the world moment by moment. This makes us less prone to false assumptions, but overwhelmed by constantly processing new information.

Reducing sensory input can help, but what helps even more is to make that input familiar and predictable – to reduce prediction errors.

It also helps if we have enough time to think.

P.S. To learn more about how brains use predictions to process information, check out the excellent book Autism and the Predictive Brain by Peter Vermeulen. And to learn how the autistic way of processing can affect a person’s whole life, check out my book What I Mean When I Say I’m Autistic.

P.S. I write from my personal experience as an autistic. What I share is not a substitute for advice from an autistic medical professional. Also, some of my opinions have changed since I first wrote them.