123. Human Behavioral Biology: Where Game Theory & Evolution Collide

10 takeaways from this lecture:

00:04:41 Having  been trained, you can examine sets of skulls and accurately determine many things about the species.

While without actually examining a real giraffe mathematicians could predict the necessary size and power that a giraffe’s heart would have to be in order to sufficiently pump blood through it’s neck to reach it’s head, this doesn’t mean mother nature is amazing, it simply points out that there is an inevitable logic underlying how organisms function. This is how organisms and species evolve; by optimizing solutions and strategies to ensure survival. This is known in game theory as the Nash Equilibrium.

[EDITOR’S NOTE: For more thoughts on how game theory affects advertising and branding, read my interview with Rory Sutherland TED speaker and Vice-Chairman of OgilvyOne in London on Disruption, Emotional Branding and Behavioral Economics.]

The same logical principles that allow mathematicians to make calculations and predictions about the human body can be applied to understanding and predicting human behavior. This is referred to as sociobiology“a field of scientific study which is based on the hypothesis that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context.” 

Sociobiology is what gave rise to evolutionary psychology: “an approach in the social and natural sciences that examines psychological structure from a modern evoluationary perspective,” seeking to “identify which human psychological traits are evolved, functional products of natural selection or sexual selection in human evolution.”

00:09:08 Darwin, didn’t discover evolution; Charles Darwin, along with Alfred Russel Wallace,

came up with notions of a mechanism for evolution – natural selection:

Darwinian Evolution – traits in population change over time; enough, in fact, that you can get speciation – the “formation of new species as a result of geographic, psychological, anatomical, or behavioral factors that prevent previously interbreeding populations from breeding with each other.” Notably that the traits are:

  1. Heritable; that can be passed on from generation to generation.
  2. Variability among those traits
  3. Adaptability of those traits
  4. Mutation; possibility of random new type of trait



Application of Darwinian Evolution – Contrary to popular belief, made popular by zoologist Wynne Edwards, animals do not behave for the good of the species. In truth, animals behave for passing on as many copies of their genes as possible. This may make it appear that animals are behaving for the good of the species, but that isn’t always the case.

Is the older zebra voluntarily throwing itself to the attacking alligators to save the younger zebras, or are the younger zebras throwing the older, slower zebra to the alligators to save themselves?

00:18:47 Next you have:

  • Individual selection (selfish-genes) is the idea that sometimes the behavior of an animal is meant to optimize the number of copies of its genes that it leaves in the next generation its self-reproducing.
  • Sexual selection is the idea that animals can reproduce at a higher rate not because they possess traits that have any adaptive or survival value, but solely because they posess the physical characteristics that the opposite sex finds attractive.
  • Kin selection is the idea that traits have a higher probability of making it into the next generation when relatives and family members cooperate with each other concerning reproduction.
  • Reciprical altruism – Evolution can result in a Paper>Rock>Scissors stalemate or truce where different animals live peacefully with and leave each other alone because they keep each other in check: attacking one animal would result in being attacked by another animal. Cooperation has a strong evolutionary payoff, even among non-relatives with the condition that you’re not putting more into the cooperative relationship than you are getting: equal reciprocity.

The four selection ideas above often push against each other in the animal species. For example female fish might find colorful male fish attractive, however the less colorful fish have a greater chance of blending in and not being eaten than those colorful male fish.

[EDITOR’S NOTE: In his talk Criminal Profiling: 14 Theories of Causes & Deterrance of Criminality, Glenn Wilson points out that “15-20% of criminals are said to be psychopaths, and that psychopaths, and criminals in general, are often attractive to women.”A study in 1995 found that criminals have an average of nearly 4 children each vs 2.21 for non-criminal controls from same social classes/urban residence.)”]

This reciprical relationship can only happen with intelligent species capable of remembering who they owe favors to and who owes them a favor. If one in the relationship tries to cheat to gain an advantage over the other(s), the other(s) will remember this and be equally uncooperative in the future.

Humans tend to be quite attuned to identifying social interactions involving cheating versus social interactions involving spontaneous altruism.

The optimal strategy:

In a reciprical, cooperative relationship, when should you cooperate for mutual-benefit and when should you cheat to gain an unfair advantage?

00:41:30 Game theory is the mathematical application of probabilities to situations to identify the optimal actions to achieve the best possible outcome in any given situation.

The Prisoner’s Dilemma is an example of when two purely ‘rational’ individuals might not cooperate, even when it appears to be in their best interests to do so:

“Two members of a criminal gang are arrested and imprisoned. Each prisoner is in solitary confinement with no means of speaking to or exchanging messages with the other. The prosecutors do not have enough evidence to convict the pair on the principal charge. They hope to get both sentenced to a year in prison on a lesser charge. Simultaneously, the prosecutors offer each prisoner a bargain. Each prisoner is given the opportunity either to: betray the other by testifying that the other committed the crime, or to cooperate with the other by remaining silent. 

Here is the offer:

  • (Both cheat) If A and B each betray the other, each of them serves 2 years in prison
  • (One cheats) If A betrays B but B remains silent, A will be set free and B will serve 3 years in prison (and vice versa)
  • (Both cooperate) If A and B both remain silent, both of them will only serve 1 year in prison (on the lesser charge)”

After thousands of computer generated trials and algorythms, the solution to the prisoner’s dilemma, and the answer to the above question is Tit-for-tat: start off by cooperating with the individual. If that person cooperates with you, you begin by cooperating with that individual again in the next round, and so on until a round occurs where the person cheats against you, in which case you cheat against them the next time. If they cheat against you, you continue cheating against them until they return to being cooperative with you, at which time you return to being cooperative.

1.) Tit-for-tat (TFT): In the absence of somebody stabbing you in the back, you should always cooperate.

Tit-for-tat is not only the most optimal strategy for cooperation, it eventually drives the other strategies into extinction, and generous strategies drive selfish strategies to extinction.

Courtesy Alexander Stewart and Joshua Plotkin

Tit-for-tat is optimal because:

  • It starts off as friendly and accomodating
  • The rules of the game are clear
  • It rewards pain with pain
  • It allows each party to cheat when necessary, and to be on the lookout for cheating by the other party
  • It’s forgiving, allowing the two to return to a friendly and accomodating relationship.
  • It may lose the battles, but it ultimately wins the war: even if in a 3 round game your opponent stabs you in the back on the final round and you cannot retaliate, tit-for-tat is still mathematically the optimal strategy.

00:51:04 But the major vulnerability in tit-for-tat is that there can be noise and misunderstandings within the communication system whereby mistakes can be made and the wrong signal can be sent. One person can misinterpret an action as cheating when in fact it wasn’t, thus causing the second person to cheat in reciprication, thus throwing the entire balance off. Therefore an improvement must be made:

2.) Forgiving tit-for-tat (FTFT): In the presence of signal error, one person can forgo cheating during one round and suffering the loss to get things back on track.

00:56:02 But the major vulnerability for FTFT is when one party continues to forgo cheating to get the relationship back on track, yet the other party exploits this and continues to cheat.

3.) TFT > FTFT: Begin with a TFT relationship, and then through time as the relationship and trust grows, shift from TFT to FTFT.

4.) Pavlov: If person wins points from a round, that person will repeat their action in subsequent rounds until they are no longer winning points. Once no more points are being won, the person switches to another tactic.

Unrelated to the psychology of Ivan Pavlov, this tactic allows you to exploit people who are too forgiving.

01:02:11 This tit-for-tat game theory is also evident in animal species. Female vampire bats, for example, will all share the same nest – related and unrelated – and the female bats feed each other’s babies indiscriminently. However once scientists made it appear that one of the female bats was keeping food for herself, the other female bats refused to feed her babies.

Also, there are certain fish species, such as the Black Hamlet fish,  which can actually change sex under strategic circumstances. The problem being that it is much more difficult and energy consuming for the female to lay eggs, these fish share the burden by taking turns being male and female. In the instance where one fish isn’t doing its part of the reproduction, the other fish stop cooperating with it.

01:09:04 Of course, where there are instances of tit-for-tat with animal species, there are also exceptions, or more advanced forms of it. Lion prides in East Africa have been found to have cowardly lions who always shy away from danger, and on the surface they don’t appear to be penalized for shirking their turn in danger, yet do their part in other ways.

The naked mole rat live in big cooperative underground colonies, of which in every colony are a few mole rats who don’t do any work maintaining the colony, and yet eat the same amount of food as everybody else and don’t appeared to be penalized. However they later do their part by using their body to plug the colony entrances during the rainy season at the peril of being eaten by coyotes.

01:20:12 By simply looking at the size difference between the male and the female in a species, you can deduce much about the species:

  • In tournament species – men with more aggressive behavior and who have larger body sizes are likely because the women in that culture have been selecting mates based on aggressiveness.

5% of the males have 80% of the children.

  • In pair-bonding species, the men and women are of similar size and help raise the children together. Every man generally has a couple of kids.


Humans lie somewhere in between tournament and pair bonding species.