Have you ever stepped on to an escalator that wasn’t moving? What happens? Chances are you jolt forwards…but why? An escalator that isn’t moving is essentially just a set of stairs, but when you approach a flight of stairs you don’t jolt forward. You can clearly see that the escalator wasn’t moving, so why the jolt?

Well, your brain is a clever little predictive machine. Based on past experiences of escalators, it knows that you need to shift your weight forward when you step on one to prevent you from falling backwards. So, despite your eyes providing visual evidence that the escalator isn’t moving, your brain (as usual) thinks it knows better!

Just another example of when the brain thinks it knows better. When you read the sentences above, light from the text hits your eyes, this information is relayed to the brain which processes the information into our consciousness but not before it messes about with it a little bit first. It uses the visual information from the eyes and combines that with its own knowledge and past experience i.e. previous times these words have been seen together and in what order, and in what way they would make sense to come up with what we ‘see’ as sight. Only when we go back and scrutinise this can the brain see that is made a mistake.

What we see and hear about the world around us is really the difference between what the sensors in our eyes and ears detect, and what the brain expects or predicts to happen. The same can be true of the sensation of Pain.

Seeing is believing

Illusions are a fantastic example of how we place way too much trust in what we see and hear to be a true reflection of the world around us. When what we see and hear has a lot to do with the difference in what our brain expects to happen (based on past experiences) and what actually happens. This has been termed ‘the error in perception’ [1].

The image on the left is identical to the image on the right. The only difference being two vertical lines drawn either side of squares ‘A’ and ‘B’. In the image on the left you could be forgiven for thinking that square ‘A’ is darker than square ‘B’ but, as we can see in the image on the right, they are actually the same shade of grey. The difference; expectation. Our brain knows a lot about light and shadow so it knows that when shade is cast over a light surface, it appears darker. With this in mind, and without you having to consciously do anything, it has magically corrected this image for you…isn’t that great! What’s more, now that you know they are the same shade of grey, you still cannot convince your brain of this. In much the same way that whilst pain is also an output of the brain, it is not a choice. It is a decision that is made for you based on everything the brain ‘knows’.

It’s not just our eyes that can be fooled by an illusion, the brain can mess about with what we hear too;

….and this….

When we hear sound accompanied by visual input our brain can make assumptions that sound that might accompany it….Now try this, play the video, turn your head away from the screen and just think about the words “Brainstorm” or “Green Needle” can you control the version of the sound you hear with just your mind…..AMAZING! Forget bending spoons…you just bent sound with your mind! Uri Geller eat your heart out!

Pain is an output, not an input

Just as we don’t see with our eyes or hear with our ears; what we see and hear is an output of the brain based on visual and auditory information it receives from our eyes and ears. Our body does not tell our brain that it is in pain; our brain receives messages (nociceptive information) from our tissues, and it is the brain that processes that information into pain (or no pain!). Essentially when receiving information from the tissues the brain asks, ‘how dangerous is this?’ and to help it answer this question, it uses not only the information it is receiving from the tissues in the body but also it’s own knowledge and predictions based on past experiences, your current situation, what could an injury in that area mean for you, your life, or your livelihood. If it concludes that there could be something dangerous going on, you will feel pain, if it concludes that there is nothing to worry about, you won’t!

So there you have it, pain in a nutshell. It is as simple and complicated as that. In fact, it is very complicated. Which is what can make treating pain so difficult for some people. About 1 in 4 people experience persistent pain issues. Pain is an output of the brain, but as we saw in the visual illusions above, it is not a choice. Nobody would ‘choose’ to be in pain. We must find ways to make our brain more likely to interpret these ‘danger’ signals differently; in other words we have to do more things that make us feel ‘safe’.  If this is you, speak to an up to date healthcare professional about your problem. They can help you and give you the tools to live a life with less pain.

[1] https://www.noigroup.com/noijam/predictive-processing-a-potential-theory-for-persistent-pain-and-the-power-of-discrepancy-in-facilitating-change/