Control systems, what are they?


Imagine a little room with two instruments. One checks the temperature of the room and displays it, the other is just a simple device with a slider that controls the temperature of the room.

One more thing: there is another display above the door to this room that shows a certain temperature. Now somehow you end up in this room and your goal is to match the temperature of the room to the one shown above the door.

Well that is easy enough right? Just check the display above the door, compare it with the instrument that has the actual temperature of the room, if it’s too hot pull the slider to the left, if it’s too cold pull the slider to the right. Piece of cake. Once the desired temperature is reached, balance the slider so it heats exactly the amount that leaves the room.


Now that is already a basic control system. In order to relieve you of this painful duty we can automate this process and call it a thermostat. What we do when we turn the knob on our heaters at home is change the display above the door, not the position of the slider! That’s what the thermostat does for us. We simply say make the room this temperature, the thermostat will regulate the heat output accordingly.

That is one of the defining features of control systems, they are goal directed. It doesn’t matter how it gets there but what matters is that in the end the room is a certain temperature, that our desired state is reached. This makes things a whole lot easier, it abstracts the process and spares us the details. All we have to do is specify the goal state. The system will do the rest.

Aaaaand of course we have to design the system in the first place. But that’s what it’s all about, designing things in such a way that they are simple and easy to use and work. And you have no idea how much crazy shit is actually going on in the background, like the user interface to a computer.


Okay so you may be asking yourself, why the hell is this guy so damn interested in thermostats that he actually writes a blog post about it?

Well I want to propose that the brain is just one big fucking thermostat.

What if all we do in life is simply to take care of our body? That’s our top desired goal, our control state. Everything else is just a means to get there. In the end it doesn’t matter one bit how you fill your day, the only thing that is important is that you are content and happy with the way things are.

Imagine that room I described getting ever more and more features. More ways of controlling the temperature, more precise ways of sensing it, being able to actually predict that the temperature will rise an hour before it does so. More effectors that can change things beyond the confines of the room, making the environment more stable in order to control the temperature even better.

Before you know it this room is growing a brain and building insulated houses, constructing sophisticated heating, putting on clothes, all just because it wants to keep the damn temperature at a desired level. Okay, yes our room is probably not going to grow a brain, but that’s how evolution did it.


Now you may say well temperature is a rather trivial example, what do I care about temperature, that’s not really what I focus on in life. Go out naked in -10 degrees and then we can keep talking. You only notice it of course when something is wrong, when your desired state is not your perceived state. But alas there is much more to life than not freezing. That’s what I wanted to get at with our simple room getting much more sophisticated. The focus shifts from using the basic slider to control the temperature to all the new and more complex things like controlling the temperature outside of the room even though the reason you are doing all that is still the same: to keep the room temperature at a certain value.

We don’t need to focus on the things we have mastered. Walking and talking is pretty easy but still took very long to learn as a child. And the goals you had as a child such as satisfying your hunger and yearning for physical contact are still there but are now fulfilled at a much higher level, you are content when you are making money because you know that this ensures you a supply of food and the cozy, warm environment of a house.

The simple goal of a system to control certain variables of its environment, to maintain homeostasis, to keep on existing, can give birth to such an immense variety of strategies to achieve this, from simple cells, bacteria, viruses, then multi-cellular organisms, their body forms, information systems, means of perception, means of action, complex sequences of behaviour, societies, cultures. All just to fulfill that one goal of multiplication and therefore continued existence. The means change, the end remains the same.


What’s the big deal though? How does this help us in understanding the brain?

Knowing what the goal of a system is, having a framework in which to fit our findings really helps us to understand how it works! Let’s take a look at perception and action for example.

In our simple room we had a display for the current temperature, a slider to adjust the heat output and another display above the door for the desired temperature. Perception in this case is the process of correctly showing the current temperature of the room. Action is changing the slider and therefore the heat output. Now what is our display above the door? It’s not a perception since it has nothing to do with the outside world, the actual temperature. But neither is it action, it doesn’t really do anything by itself, it relies on the slider to change the temperature. So we can think of this as an intermediate stage between perception and action, namely cognition: Which actions do I have to take in order to change my perceptions?

And that is the important part! Action and perception are intimately linked. In the end action is about changing your perception of the world to match your expectations (the desired temperature). And you can do this either by changing the actual world (pulling the slider), or changing your perception of it. That is why perception is a very active process. The display in our room showing the current temperature is a control system itself, it has a value which it thinks is the current temperature and it compares this to an actual input. If nothing has changed it will keep displaying its proposed value, if not it will take action and change its display to the new value.


I want to conclude this post with a quote by Gary Cziko out of his book Without Miracles:

“A control system does not control what it does; it controls what it senses”

This really shows the changed perspective of looking at the brain as being a control system. It cares about what it senses and every action it performs is only done in order to change a perception. The outcome is important not the individual action. This fits perfectly into the hierarchical nature of the brain, more abstract and complex goals arising the higher up you go. You may just have doing the groceries as your intended goal or your control state. But this is already a highly complex act which involves planning your route, planning what you need to buy, taking a bag with you, going out of your home, getting on a bike, riding to the grocery store etc. All just because you want a certain outcome.

In the end you perceive a full refrigerator and you are happy. Everything is as it should be.

That’s all intelligence really is, finding the means to your ends.

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