WEBVTT

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How do schools of fish swim in harmony?

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And how do the tiny cells in your brain
give rise to the complex thoughts,

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memories,

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and consciousness that are you?

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Oddly enough, those questions have
the same general answer:

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emergence,

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or the spontaneous creation of
sophisticated behaviors and functions

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from large groups of simple elements.

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Like many animals, 
fish stick together in groups,

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but that's not just because
they enjoy each other's company.

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It's a matter of survival.

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Schools of fish exhibit 
complex swarming behaviors

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that help them evade hungry predators,

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while a lone fish is quickly singled out
as easy prey.

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So which brilliant fish leader
is the one in charge?

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Actually, no one is,

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and everyone is.

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So what does that mean?

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While the school of fish is elegantly
twisting, turning, and dodging sharks

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in what looks 
like deliberate coordination,

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each individual fish is actually
just following two basic rules

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that have nothing to do with the shark:

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one, stay close, but not too close
to your neighbor,

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and two, keep swimmming.

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As individuals, the fish are focused on
the minutiae of these local interactions,

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but if enough fish join the group,
something remarkable happens.

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The movement of individual fish 
is eclipsed by an entirely new entity:

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the school, which has its own
unique set of behaviors.

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The school isn't controlled
by any single fish.

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It simply emerges if you have enough fish
following the right set of local rules.

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It's like an accident that happens over
and over again,

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allowing fish all across the ocean
to reliably avoid predation.

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And it's not just fish.

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Emergence is a basic property of many
complex systems of interacting elements.

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For example, the specific way in which
millions of grains of sand

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collide and tumble over each other

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almost always produces the same
basic pattern of ripples.

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And when moisture freezes
in the atmosphere,

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the specific binding properties
of water molecules

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reliably produce radiating lattices
that form into beautiful snowflakes.

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What makes emergence so complex

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is that you can't understand it
by simply taking it apart,

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like the engine of a car.

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Taking things apart is a good first step
to understanding a complex system.

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But if you reduce a school of fish
to individuals,

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it loses the ability to evade predators,

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and there's nothing left to study.

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And if you reduce the brain 
to individual neurons,

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you're left with something that is
notoriously unreliable,

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and nothing like how we think and behave,

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at least most of the time.

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Regardless, whatever you're thinking about
right now

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isn't reliant on a single neuron
lodged in the corner of your brain.

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Rather, the mind emerges from
the collective activities

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of many, many neurons.

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There are billions of neurons 
in the human brain,

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and trillions of connections between
all those neurons.

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When you turn such a complicated
system like that on,

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it could behave in all sorts
of weird ways, but it doesn't.

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The neurons in our brain follow
simple rules, just like the fish,

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so that as a group, their activity
self-organizes into reliable patterns

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that let you do things 
like recognize faces,

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successfully repeat the same task
over and over again,

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and keep all those silly little habits
that everyone likes about you.

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So, what are the simple rules 
when it comes to the brain?

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The basic function of each neuron
in the brain

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is to either excite or inhibit
other neurons.

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If you connect a few neurons together
into a simple circuit,

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you can generate rhythmic patterns
of activity,

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feedback loops that ramp up
or shut down a signal,

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coincidence detectors,

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and disinhibition,

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where two inhibitory neurons
can actually activate another neuron

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by removing inhibitory brakes.

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As more and more neurons are connected,

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increasingly complex patterns 
of activity emerge from the network.

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Soon, so many neurons are interacting
in so many different ways at once

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that the system becomes chaotic.

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The trajectory of the network's activity
cannot be easily explained

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by the simple local circuits
described earlier.

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And yet, from this chaos,
patterns can emerge,

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and then emerge again and again
in a reproducible manner.

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At some point, these emergent
patterns of activity

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become sufficiently complex,

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and curious to begin studying
their own biological origins,

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not to mention emergence.

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And what we found in emergent phenomena
at vastly different scales

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is that same remarkable
characteristic as the fish displayed:

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That emergence doesn't require
someone or something to be in charge.

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If the right rules are in place,

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and some basic conditions are met,

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a complex system will fall into
the same habits over and over again,

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turning chaos into order.

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That's true in the molecular pandemonium
that lets your cells function,

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the tangled thicket of neurons
that produces your thoughts and identity,

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your network of friends and family,

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all the way up to the structures and
economies of our cities across the planet.