The Rational Animal: How Evolution Made Us Smarter Than We Think

by Kenrick, Douglas T.

  ERASING ERRORS BY ENGAGING THE AFFILIATION SUBSELF

  Daniel Kahneman and Amos Tversky make up the dynamic duo whose groundbreaking research in judgment and decision making garnered a Nobel Prize. Among their many contributions to behavioral economics, they are known for devising a number of particularly clever questions to expose the fallibility of human reasoning. One such question goes like this:

  Imagine that the United States is preparing for the outbreak of an unusual Asian disease, which is expected to kill six hundred

  people. Two alternative programs to combat the disease have been proposed.

  Program A: If Program A is adopted, two hundred people will be saved.

  Program B: If Program B is adopted, there is a one-third probability that six hundred people will be saved and a two-thirds probability that no people will be saved.

  Which of the two programs would you favor?

  The first thing to notice is that both options have the exact same “expected value” for the average number of people who are expected to remain alive—two hundred out of six hundred. The difference between the two options is this: whereas Program A provides a precise number for how many people are going to be saved for certain, Program B is fraught with uncertainty. Tversky and Kahneman found that the majority of people (72 percent) chose the more certain Program A.

  But discovering that people like the more certain option didn’t win them the Nobel Prize. The important twist is what happened next. A second group of people were given the same Asian disease problem and provided with the same options. But the options were framed just a little bit differently:

  Program A: If Program A is adopted, four hundred people will die.

  Program B: If Program B is adopted, there is a one-third probability that nobody will die, and a two-thirds probability that six hundred people will die.

  Which of the two programs would you favor?

  It’s critical to note that this second problem is logically and mathematically the exact same problem as the first one. Again, both options have the same expected value for the average number of people who are expected to remain alive—two hundred out of six hundred. The only difference is that the options are never framed as losses instead of gains. However, when presented with the latter two options, the majority of people (78 percent) now chose the less certain option B. This preference reversal seems to reveal a blatant miscalibration in decision making.

  People’s fickle preference reversal in the Asian disease problem is often presented as a hallmark of human irrationality and a crushing blow to the central assumptions of the classical economic model of rational man. It’s not that people are bad at math (the numbers in the problem are intentionally round so that all college students can easily calculate the expected values in their head). Instead, people just seem irrationally inconsistent in dealing with mathematically identical decisions.

  But before we close the case and conclude that educated individuals are mostly moronic decision makers, let’s do a little detective work with our evolutionary magnifying lens. We know that our ancestors lived in bands of one hundred people or fewer. And we know that our brains are not designed to comprehend large numbers. Remember, our ancestors would not have encountered such quantities.

  Decision scientist X. T. Wang suspected that the classic Asian disease problem might be an evolutionarily novel contraption that fails to tap our deeper ancestral logic. Wang thought that the problem is like asking an illiterate person to write, or like asking Doug and Vlad to perform a few ballet movements from Swan Lake (take our word for it, you don’t want to see either of us in tights).

  Because the size of hunter-gatherer groups rarely exceeded one hundred people, Wang reasoned that people might respond to the problem very differently if it involved numbers that would have made sense to our ancestors. What if, rather than six hundred people, the problem involved sixty people—a number within the range that our ancestors’ affiliation subselves had to deal with?

  Wang performed an experiment in which he presented people with the exact same problem that Kahneman and Tversky used. The only difference was that the number of people in Wang’s question now approximated the size of an ancestral band. Subjects in the study had to decide between one program that would save twenty people versus another program with a one-third probability that sixty people would be saved (with a two-thirds probability that no people would be saved). Others needed to choose between having forty people die versus taking a chance on a program with a one-third probability that nobody would die (and a two-thirds probability that sixty people would die).

  Wang made a surprising discovery. When the size of the group was sixty (rather than six hundred), the framing made no difference in people’s choices. Whether the problem was framed as a loss or a gain, people consistently made the same choices. Wang’s findings throw a monkey wrench into the model of humans as irrationally fallible by showing that people are perfectly capable of avoiding errors. The trick is to ask questions in an ancestrally relevant way.

  HOW TO HELP SUICIDAL TURTLES (AND IRRATIONAL HUMANS)

  Sea turtles lay their eggs on dry, shallow beaches. The eggs hatch in the wee hours of the night, with hundreds of hatchlings crawling down the beach toward their ocean home. It’s a glorious sight. As Crush, the turtle in Finding Nemo, explains in his charming surfer accent, “Oh, it’s awesome, Jellyman. The little dudes are just eggs, we leave ’em on a beach to hatch, and then, coo-coo-cachoo, they find their way back to the big ol’ blue.”

  But recent generations of sea turtles have been making some awesome errors in their decision making. When presented with the option of crawling either toward the ocean or away from the water onto asphalt full of oncoming eighteen-wheelers, thousands of turtles have been choosing the latter, fatally irrational option.

  A Florida man was recently inspired to find a cure for this new wave of chelonian self-destructiveness. A news article titled “Fort Lauderdale Saves Turtles from Suicide” explains his radical solution for reducing turtle decision errors: turning off the distracting lights.

  Turtle hatchlings have, it seems, evolved to crawl toward the light. For millions of years this was a highly rational and effective strategy because the light on a dark beach represented the reflection of the moon and stars on the water’s surface. Following the lights led baby turtles back home to the sea. The problems started when humans began building beachfront homes and sparkling hotels on the other side of the beach. Now after hatching, Fort Lauderdale’s turtles heading for the brightest nearby lights were being guided straight into traffic.

  Are self-destructive sea turtles naturally irrational? Yes, in the modern world. But there’s a deeper truth. Turtles are basing their decisions on simple cues that were perfectly rational for their ancestors; these days, however, their evolved decision-making mechanisms are being blinded by modern lights.

  Modern humans have something in common with suicidal turtles. We too have deeply rational decision-making mechanisms, and our machinery is also sometimes blinded by features of the modern world.

  Behavioral economists and psychologists studying judgment and decision making have constructed a hilarious house of errors, often showing with great fanfare that humans are like suicidal turtles. Step right up, folks, and see the amazing Stupidman! Just pay your $20 and look in the mirror! And for a mere $50, you can look twice!

  But lost in this carnival of human idiocy is a deeper truth about humanity: not only is Homo sapiens one of the most successful species on the planet (suggesting that we’re doing something right), but we hominids have mastered extraordinarily complex problems such as speech perception, grammar induction, and facial and object recognition, outperforming the most powerful computers.

  When blinded by modern lights, though, we too can fail at many simpler tasks. But many of our errors and irrationalities are less the fault of our abilities and more the fault of the disabling ways our abilities are tested. By making small alterations to present inf
ormation in ancestrally relevant ways—by turning off the blinding lights—even we seemingly dim-witted dodos can be instantly transformed into deeply rational savants.

  ALTERING DIFFICULT QUESTIONS to tap into our wise ancestral psychologies can drastically decrease errors and improve our decisions. But it turns out that the same decision can be deeply rational for one person and irrational for another. We next take a closer look at a fundamental biological difference between two types of people. To see why this matters, we start by asking a simple question: Why do people who go from rags to riches often later end up in bankruptcy court?

  6

  Living Fast and Dying Young

  CHANCES ARE YOU have heard of Stanley Burrell, though you might not recognize him by that name or know all the details of his fascinating life story. Raised by a single mother, Burrell grew up with eight siblings crammed into a small apartment in the East Oakland housing projects. To earn money, the young Burrell sold stray baseballs and danced with a beat box in the Oakland Coliseum parking lot. His energy and flair were so infectious that after seeing him rouse fans while doing splits, Charles O. Finley, owner of the Oakland A’s major-league baseball team, hired eleven-year-old Stanley as a batboy. One of the players thought the new batboy bore a resemblance to baseball legend Hammerin’ Hank Aaron, so they started calling him “Hammer.”

  By age twenty-seven, Stanley had channeled his performing energies into a career as a superstar musician, known to the public as MC Hammer. The masses went wild over his flamboyant dance moves, trademark parachute pants, and hits such as “U Can’t Touch This.” In 1990, Forbes magazine estimated that the once-poverty-ridden Burrell, having sold over 50 million records, was worth $33 million.

  Yet only a few years later, in 1996, Burrell was forced to file for bankruptcy. He had not only lost all that fortune but was now $13 million in debt. While Hammer was an adept master of ceremonies (earning him his “MC” moniker), he could not master the concept of saving. His expenses included a Xanadu-like twenty-acre California compound complete with tennis courts, two pools, a built-in movie theater, a seventeen-car garage, and a sound system that required twenty-two miles of wiring. He also felt compelled to purchase several racehorses, a helicopter, and solid gold chains for his four Rottweilers. But he didn’t limit his lavish spending to himself: maintaining the Hammer hype required an entourage of two hundred people at a yearly cost of $6.8 million.

  MC Hammer is not unique in his journey from rags to riches to bankruptcy. According to an article in Sports Illustrated, 78 percent of professional football players will go bankrupt in their lifetimes, and 60 percent of pro basketball players are broke within five years of retirement. This is despite the fact that the minimum yearly salary in the National Football League is $375,000. And for players in the National Basketball Association, the average salary is a whopping $5.15 million a year.

  Where does all the money go? New York Knicks center Patrick Ewing once explained it this way: “We make a lot of money, but we spend a lot of money too.” Boxer Mike Tyson epitomized the big-spending athlete, dropping $188,000 for two white Bengal tigers (to wrestle for fun), shelling out a cool $2 million for a single bathtub for one of the thirty-eight bathrooms in his mansion, and buying a house with seven kitchens and its own nightclub—only to stay there one night. Although Tyson earned over $300 million during his fighting career, he was over $24 million in debt when he filed for bankruptcy in 2003.

  The compulsion to splurge is not limited to athletes or entertainers. The book The Millionaire Next Door reveals that many well-respected professionals, including doctors, spend more than they earn, often ending up broke later in life. Even longtime CNN interviewer Larry King was forced to declare bankruptcy when he couldn’t pay his debts, although it didn’t prevent this former poor boy from Brooklyn from racking up still more debt—and more wives (King is currently on his eighth bride).

  Why do so many people who strike it rich not only fail to save for the future, but spend so outlandishly beyond their means? Although many of these impulsive choices might appear foolish and irrational, let’s consider how living for the moment and spending like there is no tomorrow may reflect a deeper rationality. Here we examine the evidence that different people are disposed to follow very different strategies in life. Some, like MC Hammer, aspire to race up from rags to riches, following a “fast” trajectory associated with risk raking, impulsivity, and a dangerous lifestyle that can often lead to early death. Others are on the “slow” path, which involves delaying gratification and playing it safe. Neither strategy is intrinsically better; rather, each one makes the best of the circumstances into which people were born. Understanding these two strategies—and the circumstances that produce them—is important because they explain why the same decision can be irrational and maladaptive for one person, yet completely rational and adaptive for another.

  LIFE HISTORY THEORY

  Although more money doesn’t always lead to more problems, the question of how to spend money can present a dilemma. If you have $100, for example, you can spend it on many different things: you can stock up on food, buy a few dozen long-stem roses for your loved one, invest in a couple of violin lessons for your child, buy a new outfit that might include a pair of parachute pants, or even download MC Hammer’s complete music catalog, including his 1992 hit “2 Legit 2 Quit” and its accompanying ten-minute music video, which cost $2.5 million to make (an unheard-of price tag back in 1992). The dilemma arises because money is a limited resource. If you have only $100 to spend, you can’t fill your entire refrigerator with food and buy a new outfit and pay for violin lessons for your kid. When it comes to allocating limited resources, you have to prioritize some things over others.

  Limited resources are not limited to money. Time is a limited resource, as is the caloric energy contained in food. Decisions about how to use each resource require us to make trade-offs. If you have one hour of time, for example, you can spend it playing with your kids or responding to a batch of e-mails or taking a nap. The time spent on one activity cannot be spent on another. Similarly, if you consume one hundred calories’ worth of energy, your body can use it to do maintenance work on your immune system, or it can move your muscles (you can dance in your parachute pants), or it can store the energy in your own personal fatty savings account for later use.

  Our friends the rational economists have devoted an entire field of study—microeconomics—to understanding how individuals and firms allocate limited resources. Microeconomics is generally concerned with the decisions of people, but the need to allocate limited resources is not limited to human beings. Be it a single-cell bacterium, a Rottweiler, a Bengal tiger, or a long-stem rose, every living organism must make trade-offs. And it turns out that the underlying trade-offs faced by humans are the same as those confronted by all species.

  To understand how organisms of all sorts allocate their limited resources, biologists have developed a powerful set of ideas called life history theory. Life history theory is like microeconomics, except that it’s about biological trade-offs. The theory addresses questions like these: How long should an individual animal grow and develop before it starts to make babies? Should that animal allocate resources to caring for those offspring after they are born? If so, how much care should the animal invest in the offspring before leaving them to fend for themselves?

  According to life history theory, the fundamental tasks of life for all organisms are divided into two broad categories: somatic effort and reproductive effort. Somatic effort is the energy an animal expends to grow and maintain a healthy body (the “soma”). Reproductive effort is the energy spent to replicate the organism’s genes. You can think of somatic effort as like depositing money into a growing bank account. Reproductive effort, on the other hand, is like withdrawing money from that bank account to spend in ways that will help replicate one’s genes. Just as people don’t save money merely for the sake of generating a large bank account, animals don’t invest in soma
tic effort merely to have a large body. Instead, investment in somatic effort is investment in future reproduction. By building a larger bank account now, an animal can create more successful offspring in the future.

  Life history theory highlights how all animals make the same underlying trade-offs. At any one point, you, your pet cat, or the sparrow nesting outside your window can spend limited resources on either somatic or reproductive effort.

  Different animals resolve this trade-off in different ways, leading to what are known as different life history strategies. Some animals follow a “slow” life history strategy, investing a great deal of time and effort in somatic development before turning to reproduction. Other animals follow a “fast” strategy, skimping on somatic investment to reproduce faster. For example, tenrecs (hedgehoglike mammals found in Madagascar) are on the fast path, reaching sexual maturity only forty days after birth. As soon as they are physically capable, tenrecs become prolific replicators, generating litters of young as large as thirty-two at a time. Elephants, on the other hand, are on the slow path, taking a hundred times longer to reach sexual maturity. Even after they are physically ready, elephants might wait years more to produce young. And when they do finally get around to it, they have one offspring at a time and then wait many more years before making a sibling for little Dumbo.

  We humans are closer to elephants than to tenrecs in our life histories. We invest a great deal in somatic development, biding our time before we reach sexual maturity. Even after our bodies mature, we may wait anywhere from a few years to many decades before having children. And like elephants, we typically dedicate a great deal of energy to parenting, caring for our slowly maturing, large-brained babies—helpless little things that historically have not thrived without resources provided by both mothers and fathers.