The Rational Animal: How Evolution Made Us Smarter Than We Think (10 page)

If you’ve ever taken a course in economics or social psychology, you’ve heard about the
prisoner’s dilemma
, a prototypical example of game theory in action.
Imagine you are a crook.
One day you and one of your criminal associates are arrested on suspicion of a crime, and you are held in separate rooms.
The district attorney comes into your
cell and offers you two options: you can remain silent or confess.
By remaining silent, you will be cooperating with your partner on the standard criminal pact of silence, whereas by confessing, you will be defecting on your partner.

So do you cooperate with your partner and keep mum, or do you defect and snitch?
For both of you as a pair, you get the best joint outcome if both of you cooperate and say nothing.
If the two of you keep your mouths shut, the worst you’ll get is a short prison sentence (the DA doesn’t have enough evidence to put both of you away for a long time).
If both of you defect and snitch on each other, you’ll both get a substantially longer sentence.

But the decision poses a dilemma: If you remain silent while your partner confesses, things will turn out really badly for you.
You will be put behind bars for a long time, while your partner strikes a plea bargain and gets to walk away.
On the other hand, if your partner remains loyal and stays quiet, but you choose to confess and give the DA evidence against him, you get to go free!
Your outcome depends not only on what you do but also on what your fellow felon does, making this the kind of dilemma ideally suited for game theory.

Researchers often study prisoners’ dilemmas in the laboratory, offering people different amounts of money for cooperating versus defecting.
For example, if you and the other person in an experiment both choose to cooperate, you each get $5.
But if you both defect on one another, you walk away with only $2.
That might make it seem like cooperation is the best strategy, but it isn’t.
If you choose to defect but your partner cooperates, you win $8, while the other guy gets $0.
Of course, if the reverse happens (you cooperate but your partner defects), you’re the one who ends up with zilch—this is known as the “sucker’s payoff.”

From the rational economist’s perspective, the most reasonable decision in this type of one-shot prisoner’s dilemma is to defect.
Defecting is rational because it gives you a relatively better payoff regardless of what your partner decides to do.
If you defect, you’ll be better off in the event that your partner either defects (you get $2 as opposed to $0) or cooperates (you get $8 instead of $5).
According to the logical rules of game theory developed by rational economists, the rational
choice is for people to defect on their partners because no one should choose to be the sucker.

Although game theory is all very logical and precise, behavioral economists and other psychologists who have studied these kinds of dilemmas point out one little problem.
Real people don’t play like rational economists say they should.
Even in one-shot games with complete strangers who can’t see or hear one another, and who will never meet, real people often spontaneously decide to cooperate.

We humans fail to behave rationally in all kinds of negotiations.
In one economic game called the
ultimatum game
, you are given a sum of money (say, $100) that you need to split between yourself and another player.
The other player has no say in how much you give, except that if he or she says, “No way,” to your offer, neither of you gets a penny.
Rational economists have argued that your most reasonable choice would be to offer very little to the other player, maybe $1 for the other person and $99 for you.
Why?
Because if she says yes, she gets $1; if she says no, she gets $0.
So, as long as she chooses rationally, you have her over a barrel.
Yet people who are offered a $1 share of $100 usually respond with what rational economists would consider irrational spite, saying, “No thanks.
I’ll take $0 instead!”
In fact, not only do people making offers in the ultimatum game rarely act like rational economists say they should, but capitalistic Americans are surprisingly generous in their offers, often sharing equally with the other person (the one exception is that students of economics tend to play hardball, and consequently tend to leave the experiment with less money than less “rational” people).

Behavioral economists, the laboratory decision scientists who have exposed our supposed defects, have dedicated thousands of pages in scientific journals to these kinds of “anomalies,” “fallacies,” and “paradoxes.”
But do these violations of economic rationality really mean that humans are flawed?
From the evolutionary psychologist’s perspective, there is something deeper going on.

The rules of game theory developed by rational economists make good sense when the parties negotiating with each other are cold-blooded Econs, each seeking to maximize monetary returns.
These rules work well in explaining how the Coca-Cola and Pepsi-Cola Corporations
compete in the marketplace, how used automobiles are bought and sold on the open market, and how Wall Street traders exchange shares of stock or swap pork bellies on the Chicago Mercantile Exchange.
But humans are not cold-blooded Econs.
Corporations, market pricing, and even economics itself are all evolutionarily novel phenomena—things our ancestors would never have encountered.
What our ancestors did encounter was their kith and kin.
Even today, most people in the world still have most of their meaningful interactions with friends and family members.
Rather than playing the rational economist’s game, we play a very different game when it comes to family.

HOME ECONOMICS: THE KINSHIP GAME

What would happen if you were playing the prisoner’s dilemma game, but the other prisoner was your clone?
Nancy Segal has actually studied this very question.
Segal is a behavioral geneticist at California State University, Fullerton, just up the road from Disneyland.
Segal studies twins.
She looks at the similarities and differences in twins’ preferences and behaviors, like whether twins separated at birth have similar personality traits when they are reunited thirty years later.
Segal believes that studying the relationships between twins offers an unusual opportunity to study one of evolutionary biology’s most powerful principles:
inclusive fitness
.
The idea is simple: because evolution favors behaviors that help an organism pass on its DNA, natural selection favors greater cooperation between organisms who share common genes.
Since we share some of our genes with relatives, this means that helping a relative is, from a genetic perspective, almost as good as helping ourselves.

The principle of inclusive fitness provides the scientific explanation for why blood is thicker than water.
But the principle doesn’t just say that people will help family members more than strangers.
It is much more precise: people will tend to give more help to those family members who share more genes with them.
For example, if you’re going to run into a burning building to save another, the principle of inclusive fitness suggests that risking your own life will be genetically worthwhile if you can save two siblings (each sharing about half, or
0.5, of their genes with you), four nephews or nieces (each sharing one-quarter, or 0.25, of their genes with you), or eight cousins (each sharing one-eighth, or 0.125, of their genes with you).

Hundreds of findings across the animal kingdom support this principle.
Ground squirrels are more likely to risk their lives by giving a loud alarm signal to warn of a predator if doing so will save their brothers and sisters, as compared to their second cousins.
White-fronted bee-eaters are more likely to share food with full siblings than with half siblings.
And aid within human families tends to run along genetic lines as well.
Of the inheritance money left in people’s wills, 92.3 percent goes to family and only 7.7 percent to nonfamily.
And of the money left to genetic relatives, 84 percent goes to those sharing 50 percent of the benefactor’s genes, 14 percent to those sharing 25 percent, and less than 2 percent to those sharing 12.5 percent or fewer genes.

The power of shared genes shows up in bold relief if you compare the way parents treat children who are related to them by blood as compared to by marriage.
In the classic fairytale, Cinderella’s nasty stepmother treats her like a lowly servant, all the while showering rewards and affection on her two evil daughters.
Sadly, the real world resembles the cruel fairytale.
Parents are 5.5 times less likely to help pay college costs for stepchildren versus biological children.
And while they are shut out of many rewards, stepchildren are often dealt more than their share of punishments.
Children living with a stepparent are forty times more likely to suffer physical abuse than those living with two genetic parents, with much of the abuse coming from the stepparent.
Even more shocking are the data on homicides.
Although murders of small children are rare, children living with a stepparent are forty to one hundred times more likely to be killed!
Is this because stepchildren live in poorer families, or because of some other confounding variable?
No.
Even for parents who have both biological children and stepchildren living with them in the same house (for whom all the possible confounding variables are equated), stepchildren are nine times more likely to be abused than biological children living under the same roof.

Nancy Segal, the twins researcher, wondered whether the principle of inclusive fitness would apply to the extreme case in which siblings share
more than the usual number of common genes.
To explore this question, she compared identical (or monozygotic) twins with fraternal (or dizygotic) twins.
While both types of twins tend to be born into the same family at the same time, they differ in the proportion of genes they share.
Fraternal twins share the usual brotherly 50 percent, while identical twins share 100 percent of their genes.
Identical twins are in fact clones.

In her research, Segal repeatedly finds that identical twins have closer and more cooperative relationships than fraternal twins.
Identical twins feel closer to one another’s children than fraternal twins.
And when a member of a pair of identical twins dies, the surviving twin feels a more intense and longer sense of mourning than that felt by the surviving member of a pair of fraternal twins.

In one study, Segal and her colleague Scott Hershberger had twins play a prisoner’s dilemma game.
To be consistent with the economic rules of the game, the researchers gave the twins instructions designed to encourage self-interested play, explaining that each person’s goal should be to win as much money for him- or herself as possible and not worry about what happens to the other player.
Yet even when spurred to think about maximizing their own self-interest—rational economist style—the twins had a hard time defecting on one another.
Instead, they spontaneously chose to cooperate much of the time.

The most interesting finding was the difference in cooperation between twins who shared half versus all of their genes.
Compared to fraternal twins, identical twins were 27 percent more likely to cooperate.
We’re not suggesting that twins were making relatedness calculations in their head before they decided to cooperate.
Identical twins simply feel more cooperative toward one another than fraternal twins, in the same way that most of us feel more willing to lend money to a sibling (who shares 50 percent of our genes) than to Cousin Myrtle (who shares only 12.5 percent).

The twin study shows not only that blood is thicker than water but that the blood of genetically closer kin is thicker than that of less closely related kin.
Our preference for those who share our genes is not simply due to the fact that we have spent more time with our closer relatives.
Even after being raised separately and then reunited, identical twins regularly become closer to one another than do reunited fraternal twins.

HOME ECONOMICS VERSUS CORPORATE ECONOMICS

Let’s go back to the Disney example and consider the two different pairs of men who ran the company.
The founding brothers, Walt and Roy O., had many disagreements and fierce negotiations, but they found a way to cooperate and stuck together through a lifetime of ups and downs.
Roy E.
and Michael Eisner, however, were unwilling to see eye to eye; instead, they aired their dirty laundry in public and let the company and its image flounder.

Each of these conflicts can be analyzed using game theory.
Let’s say that Eisner and Roy E.
are playing the prisoner’s dilemma in the laboratory and can win up to $100.
The situation is a zero-sum game: If Eisner receives $100, that’s $100 that Roy won’t get.
If Roy gets a larger payout, on the other hand, Eisner will have to take less money.
The rules of rational economics predict that when interests conflict, the best strategy for each player is to defect—to avoid being the sucker.
Roy E.
and Eisner followed the rules of the game perfectly, playing with pure self-interest and generating a relatively dismal outcome.

But now consider the case of two brothers, like Walt and Roy O., playing the same game.
Unlike Eisner and Roy E., the two brothers share 50 percent of their genes.
This is important because, from an evolutionary perspective, if your brother benefits, so do you.
Anything that contributes to your brother’s survival and reproduction gets tallied in your own evolutionary success ledger.
This makes the dilemma a positive-sum game: a $100 benefit for your brother is a $50 benefit for you.
Indeed, sometimes a family member can still win by losing.

When one of the authors of this book, Doug, and colleagues Federico Sanabria, Jill Sundie, and Peter Killeen joined to recalculate the prisoner’s dilemma in these terms, they found that the dilemma often disappeared if two brothers were playing.
Under most conditions, the deeply rational strategy was no longer to defect but to cooperate.
Thinking about this makes it easier to understand why Roy O.
was able to tolerate his brother Walt’s financial eccentricities in a way that Roy E.
could not for Michael Eisner, who was connected to the Disney clan only through dollar signs and not genes.