Complex Systems

Who directs the brain?

20 July 2017

This post is also available in: Dutch

illustration of brain as helmsman (holding ship's wheel)Our brain controls everything we do and think, and what happens in our body. Millions of things at once. But who directs the brain? Perhaps you are inclined to say: “I” do. But who is that “I”? There is no central power or police force, no editor, prime minister or CEO, no leader. The brain directs without a director.
This is very hard to imagine. It is as if all the traffic in the whole world, driving and flying and sailing and walking, were to proceed without any accidents. And with everyone arriving at their destination….almost always1. If one were to look for control mechanisms, one would find no traffic lights, signs, nothing. But how is it possible that everyone arrives at their destination? And how does useful and efficient behaviour come forth from the brain? Perhaps the following comparison may help us on the way to understanding this: how a flock of starlings is directed.

Who directs the flock?

Who directs the flock? There is no starling leader. Charlotte Hemelrijk of Groningen University has made a model of how this works2. Each bird follows a few simple rules and this leads to the whole flock flying as it does. Each starling keeps track of the seven birds that are closest to it. And it maintains an almost steady distance from these birds. Let us focus on one of the starlings in the flock. If the bird to its left swerves to the left, our starling follows. But if the bird to its right swerves to the left, our bird diverts course. In this way the movements and dynamics of the whole flock are controlled. The flock can be seen as one complex system. The many basic units ( starlings) in such a system give rise to dynamic movements. These movements are not easy to predict and can look chaotic.
Why does the flock concentrate and distort, separate and then return to formation? One reason is clear. If our starling deflects to one side, it does this with its wings in such a way that it loses height automatically. This also applies to other starlings around it. So if the flock, or a part of it, makes a turn, then (that part of) the flock descends. This is because of the body structure of the starling, which is the basic unit of the complex system. Other characteristics of the starling also exert their influence on flock behaviour. External factors, such as wind, air currents, or the approach of a bird of prey, also influence the behaviour of the flock. In the last case other rules apply than simply maintaining a constant distance in relation to your “circle” of seven.
The brain works like a flock of starlings, a complex system with simple rules for communication between the basic units, the neurons. Only, a brain is made up not of a thousand starlings, but nearly 100 billion basic units. Neurons are connected not to seven but up to ten thousand other neurons. So a brain is an infinitely larger system than a flock of starlings. And there are neurons of different sorts, with different structures. Neurons have fixed places in the brain and are grouped in nuclei. There are many more differences, of which we are unable to fully comprehend the consequences.

Too complex to understand?

How does this relate to making choices? The brain must work to produce goal-oriented behaviour, certainly when it comes to finding food, reproducing, and avoiding (life)threatening situations. The activity of the brain must be nudged in a particular direction, choices have to be made. To do this, information is retrieved from memory, and the reward system directs behavior towards the way that is beneficial to the organism. That which earlier provided food and proved to be safe is more easily chosen again. So you think, aha, the reward system directs! Yes, but there, too, you won’t find a director3.
Many people find this so counterintuitive that they do not believe it. Neuroscientists, on the contrary, are definitely convinced of this, some at all costs. I think that the problem lies in the fact that we can describe these complex systems mathematically, but do not have the words to explain how they work. The mathematical description consists of many dimensions, dozens or more. And we can grasp mental representations in a maximum of three dimensions.
Therefore, we cannot quite comprehend how a complex system like the brain works without a director. But self-organizing mechanisms, such as with the flock of starlings, do provide us with a clue.

Hemelrijk, C. K., L. van Zuidam, et al. (2015). “What underlies waves of agitation in starling flocks.” Behavioral ecology and sociobiology 69(5): 755-764.
Hemelrijk, C. K. and H. Hildenbrandt (2012). “Schools of fish and flocks of birds: their shape and internal structure by self-organization.” Interface focus 2(6): 726-737.
Frith, C. D. (2007). Making up the Mind; how the brain creates our mental world, Epilogue: Me and My Brain, The Homunculus. Blackwell Publishing.


  1. Somewhat like the scene at the Meskel square in Addis Ababa.
  2. Here you can read more about her research on starlings, fish and primates.
  3. There will be more about the reward system in later articles, showing that the term “ reward system” is an oversimplification.

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