In Scientific curiosities

What do a school of fish swimming in perfect harmony and our brain cells that give rise to an uninterrupted flow of thoughts, memories and complex knowledge have in common?

Much more than we think, as we can see in this video by Nathan Jacobs.

Both the fish that swim in a group and the neurons in our brain follow several simple rules, so that, as a group, their activity self-organizes into reliable and efficient patterns. This emergence, as scientists call it, enables fish to evade sharks and our mind to do seemingly basic things like recognizing faces, successfully repeating the same task over and over again and keeping all the little habits that people like about us.

But how do fish swim in schools, effortlessly coordinating their every move?

Each fish has a very precise perception of the environment around it, and it remains aware of its individual position within the school, deciding where and how to move depending on changes in water currents and the movement of the group. Actually, it does two things: it stays close, but not too close, to its neighbour, and it keeps swimming.

On the surface it seems that that is all there is to it, but in reality, there is much more:

As individuals, the fish are focused on the minutiae of these local interactions, but if enough fish join the group, something remarkable happens. The movement of individual fish is eclipsed by an entirely new entity: the school, which has its own unique set of behaviours. The school isn’t controlled by any single fish. It simply emerges if you have enough fish following the right set of local rules. It’s like an accident that happens over and over again, allowing fish all across the ocean to reliably avoid predation.

The astonishing thing is that emergence exists in many complex systems of interacting elements. For example, the specific way in which millions of grains of sand collide and tumble over each other, almost always creates the same basic pattern of ripples. And when moisture freezes in the atmosphere, the specific binding properties of water molecules produce radiating lattices that spread out and form beautiful snowflakes.

The group, therefore, is something much broader and creates something that is different from the simple sum of all the elements of which it is composed:

What makes emergence so complex is that you can’t understand it by simply taking it apart, like the engine of a car. Taking things apart is a good first step to understanding a complex system, but if you reduce a school of fish to individuals, it loses the ability to evade predators and there’s nothing left to study. And if you reduce the brain to individual neurons, you are left with something that is notoriously unreliable, and nothing like how we think and behave.

In the same way, whatever we are thinking about right now is not reliant on a single neuron lodged in the corner of our brain. On the contrary, the mind emerges from the collective activity of many, many neurons.

There are billions of neurons in the human brain and trillions of connections between them. When we turn such a complex system like that on, it could act in all sorts of weird ways, but it actually doesn’t.

This is the same remarkable characteristic that fish display: if the right rules are in place and some basic conditions are met, a complex system will fall into the same habits, over and over again, turning chaos into harmonious order.