The brain, what a marvelous thing in our heads. But what is it even good for?

A very sobering view of the brain is that it controls the body. That’s it, nothing more nothing less. It can change the structure of our body and make our muscles move. But what is its purpose, what is its goal? What if its only goal were to maintain status quo, meaning keeping things as they are? Regulate our body temperature: sweat when it gets too hot, shiver when it gets too cold. Keep our body weight: burn excess food, save up when food is scarce. Always getting back to a certain baseline. Maintaining its homeostasis. But what does this mean for the higher functions of the brain such as visual perception and thought? Can you even talk of a status quo in those domains? What does it mean for the brain to keep things as they are in perceiving the world? We can look at homeostasis as being an expectation. Your brain expects your body to be a certain temperature and whenever it deviates from that there is an error that has to be resolved by making changes (taking action). Similarly your brain builds up expectations about the external world, a model of the world. We don’t need to know about the law of gravity to expect that the cup we are holding will fall down and break into pieces if we let it go. We expect an apple to have a certain taste, a pillow to be soft, our mobile phones to have a certain touch. All these expectations don’t have to be conscious at all, but we notice them as soon as something is different and we get an error. The brain expects things to happen in a similar way as they have before. The brain expects things to be as they have always been, a kind of status quo. It gets used to things.

 

Habits

Habits can also be viewed as a status quo and habits are all about action. Recurring patterns of action. We get up in the morning, take a shower, eat breakfast, brush our teeth, all more or less in the same way as we always do. One step triggers the next. Habits are simply about unchanging things. So all the brain is doing is making sure things go along as they have always gone. New events are surprising, they do not meet our expectations. It already lies in the definition of something „new“. With habits it’s easy since we normally have full control over our actions. So our actions exactly meet our expectations, most of the time. But we also have lots of other expectations about our world, not just about the movement of our own bodies. Let’s take other people for example. We expect our friends to help us when we are in need, we expect our family to be caring. We might expect someone who is often violent to punch us in the face. These are all predictions based on our experiences. So a status quo builds up from experience. We expect things to be as they have always been. If something is changing, we expect it to keep changing. Like a steadily moving car. We would certainly be surprised if it abruptly stopped in the middle of the road. A status quo can therefore be pretty complicated.

 

Prediction error

But what happens when our expectations are violated? How does the brain deal with this? Let’s call this a prediction error. A prediction error is anything that is not status quo. A body temperature that is too high is a prediction error. A drop in the level of sugar in your blood can be a prediction error. Someone scaring you to death can be a huge prediction error. It all depends on your status quo. But okay we have this prediction error, now what are we going to do with it. Resolve it of course. The brain always has two ways of doing this. Either it changes its input or it changes its status quo, therefore its own internal state. What do I mean by this? In the case of body temperature it is fairly easy to explain. You are either warm-blooded or cold-blooded. You either change your input, move to a warmer or colder region or heat your body, or you change your status quo and adapt to the new input, your body becoming very cold or very warm. So you can make do with your new circumstances or fight against them to maintain your status quo! Now for higher brain functions changing our input versus changing our status quo means either taking action or learning. If we see something unexpected we can try and change it or we have to learn to predict this new circumstance.

 

Let’s look at some examples, examples are always great and easy to learn from. Imagine walking through the woods in the middle of the night and seeing something unexpected out of the corner of your eye, something weird. Now this is a prediction error but we easily resolve it by taking action, namely moving our eyes toward this anomaly and therefore changing our input. We quickly recognize that it’s just an odd looking tree or brush and not some wild animal or deadly predator. There is no need to relearn our expectations, we simply changed our input. But sometimes we just can’t change our input, in this case we have to get used to things, manage our expectations. For example being in a traffic jam every morning on your way to work. The first few times you might get pretty angry and swear and try to punch your way through but that won’t work so well. So eventually you’ll need to change your emotional expectations. You first had an expectation of getting to work in 10 minutes, now you realize that you will always need up to an hour and shift your expectation. You now have a new status quo and getting to work in only half an hour would make you surprised but happy! Changing your internal wiring and therefore your status quo is always about improving yourself and learning. You gain a new set of expectations, a new set of predictions. Another everyday example: Whenever your predictions do not match your inputs you have a prediction error. So predicting milk to be in your glass when there is none is also a prediction error. Of course the most simple thing would be to take action and pour some milk in your damn glass. Or you could be lazy and simply stop expecting there to be milk in your glass. We have a word for an emotional expectation: wanting something. Wanting to drink milk gets translated into a sensory expectation of drinking and tasting milk, since we aren’t currently tasting milk this results in a prediction error which we can resolve by taking action and pouring ourselves some milk. This is of course grossly oversimplified but the basic principle is always about resolving a prediction error, maintaining a status quo or to use a more scientific term maintaining homeostasis.

 

This view of the brain makes a lot of things easier. All we have to do is figure out how the brain predicts its inputs. Which is still a pretty damn hard task but we don’t have to ask separately how the brain processes objects, how it processes sounds, how it builds up a visual scene. It’s all the same just in different disguises. It’s all just electrical input patterns that are changing over time. The hope is to be able to find universal principles the brain uses in order to achieve maximal predictive success.

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