Evolutionary game theory | Individuals and Society | MCAT | Khan Academy

– [Voiceover] Game theory
is usually talked about in reference to decision making, but we can also use it
to talk about evolution and animal behavior. But before we do that,
I want to take a moment to talk about how game
theory is usually discussed. So when I think about game theory I generally think about it as it relates to the social sciences or maybe economics. But we can also use it to
talk about every day behavior. So imagine that we’re
watching a group of people play a game, an actual board game like maybe Monopoly or Settlers of Catan. The individuals who
are playing these games make decisions like whether or not to put a settlement on a wheat field. But the results of that
decision don’t only affect that individual player. It affects everyone who
is playing the game. So the play offs to each of the players depends upon the decisions
made by the overall group. And this is where game
theory comes into play. Because it reasons about
and tries to predict the behaviors that we would expect to see when the individuals
are playing this game. So while it looks at things
like individual strategy, it also looks at how we reason
about what the other players are going to do. Like the trades that they’re going to make or whether or not they’ll
go for longest road. So what does any of this
have to do with evolution? Well, evolutionary theory
tells us that individuals who have the best fit
with their environment will be most likely to survive
and pass on their genes. And because of this, the
genes that are best fit for the environment
will become more common within that population over
successive generations. And the important part here, at least as it relates to game theory,
is that reproduction part, because that part can’t
happen in isolation. It needs to involve others. Another thing that’s important to think about here is the environment. Because we not only need to
think about the behaviors that will allow the organism to be a fit within its physical environment, but we also need to think
about how the organism fits in with its social environment. It might need to work with other organisms to find food, or deal with
predators, or raise young. So some of the fitness
of an individual organism deals with how well
that organisms behavior matches up with the behavior of the group. So let’s think about this
in terms of game theory, where life is the game. What strategies would you expect to see from the players? Well, like it Settlers of Catan, you would expect them to be concerned with the availability
of their own resources. But you would also expect
them to be concerned about their social behavior since so much of their
well-being and chances of mating rely on their interactions with others. And this is exactly how
evolutionary game theory fits in with general game theory. Because the strategy of each individual will depend, at least in part, on the strategies exhibited
by the other players. I do however want to
point out a big difference between evolutionary game theory and general game theory. Because game theory
generally involves intention, or cases where individuals
are actively reasoning about the strategies or the
behaviors of other individuals. Evolutionary game theory is different because it is applying
this theory to situtations where there might not be any
overall conscious intention on the parts of the players. Another thing that I want to point out about evolutionary game theory is that it can actually
help us predict the traits we would expect to see in populations. Evolutionary game theory
predicts the appearance of evolutionary stable strategies, or behaviors that tend to
persist within a population once they are prevalent. So let’s thinks about this in terms of a complex behavior like altruism. So imagine that we have
two groups of monkeys. In one group, the monkeys act selfishly. When one sees a predator approaching, he takes the time to hide
and does not warn the others, which makes it more
likely that he’ll escape and that the predator will eat one of the other monkeys instead. And now on the surface it seems that this is a pretty good strategy
to ensure survival. After all, you get out of it alive. However, imagine what
would happen if the entire group behaved this way. It would mean that our monkey would be more likely to die if another monkey also didn’t sound the alarm. And, over time, this could
decimate that monkey population and reduce the fitness
of the overall group. But what if they adopted another strategy? One that involved giving an alarm call whenever a predator was spotted. The monkey that would make this call is doing this at his or her own expense, because it could draw
the predator to them. So initially you might think
that this strategy would fail. But what happens when
a monkey makes a call? It means that all of the other monkeys within that group survive. And of course it’s
possible that the monkey who makes the call survives as well. And so this actually winds up being a really successful strategy. And I want you to really think about this, because it means the altruism actually increases the success
of the overall group. So even though it might
put one individual at risk, it increases the fitness
of the community around it, making our monkey, or maybe
the kin of original monkey, more likely to survive and reproduce. And that’s why evolutionary game theory would predict the appearance
of altruism within a group.


  1. Limitbreakur said:

    the person talking in this video sounds intelligent and mature all while having the voice of a 12 year old girl.

    January 24, 2015
  2. joeyrocks79 said:

    I still dont know how to do the math for this…

    February 14, 2016
  3. TheJakecheck said:

    not just a theory… a GAME theory!

    March 11, 2016
  4. Deepali Luthra said:

    If you speak a little bit slowly, It would have been easier to understand the concept a little more. Just an advice.

    December 11, 2017
  5. Baraa Shammout said:

    thank you, good explantation

    December 26, 2017
  6. Waterboy2211 said:

    great I didnt learn a single thing. awful

    July 27, 2019
  7. V said:

    loved this. thank you so much.

    September 21, 2019

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