Selfish Reasons to Have More Kids: Why Being a Great Parent Is Less Work and More Fun Than You Think

by Bryan Caplan

  The most striking evidence on nature, nurture, and happiness comes from the Minnesota Study of Twins Reared Apart. Twins raised apart were more alike in happiness than twins raised together. If you’re happier than four out of five people, expect your separated identical twin to be happier than 67 percent of us. If the identical Pollyanna twins were separated at birth, both sets of parents would probably claim responsibility for their daughters’ happiness—and they’d both be wrong.

  The same goes for self-esteem. The single most impressive study interviewed almost 8,000 twins from the Virginia Twin Registry and found zero effect of parenting on self-esteem for both men and women. Parents try to build their kids up, but science backs the slogan that “self-esteem comes from within.”

  Finally, what about unhappiness? We’re quicker to blame our parents for our misery than thank them for our joy, but further research using the Minnesota Twin Registry concluded that nurture is equally irrelevant for both. The twins’ personality test measured many different ways to feel bad: nervous, upset, guilty, mistreated, betrayed, angry, vindictive, and so on. Upbringing didn’t matter. By the time you’re an adult, your parents’ past mistakes are not the reason for your present unhappiness.

  Parents like to think they’re giving their children the love and support they need to become happy adults. Unhappy adults like to blame their problems on their parents’ lack of love and support. According to the best evidence, however, both groups are wrong. Nature isn’t the sole author of our happiness, but nurture barely gets a word in.

  If you just can’t believe this, I know where you’re coming from. It’s easy to recall times when your mom or dad made you angry or sad. But if you’d grown up with a very different family, you’d still have a Rolodex of stories about how your parents hurt your feelings. In what sense, then, are your parents the reason for the way you feel today? You might as well just blame “life.”

  WISH #4: SUCCESS

  “Do you know, mother, I shall have our children educated just like Lucy. Bring them up among honest country folks for freshness, send them to Italy for subtlety, and then—not till then—let them come to London. I don’t believe in these London educations—” He broke off, remembering that he had had one himself . . .

  —E. M. Forster, A Room with a View

  Strangers often advise you to follow your dreams, but parents are more likely to tell you to get your head out of the clouds. Doing what you love is all well and good, but don’t you want to make something out of your life, to get ahead? Parents might add that in the long run, you’ll be happier if you take their advice. Being a successful lawyer is more fun than being a failed actor.

  I’m not taking sides here. My point is merely that parents want their children to be successful—and that doesn’t just mean “follow your bliss.” Instead, success roughly equals high income and a fancy degree. These are the kind of accomplishments parents can brag about to their friends—as in “my son, the doctor.”

  Many parents obsess over their children’s success. They don’t just help them a little with their homework. They plan out their lives, beginning with elite preschools—and use any chance they get to give their kids a leg up. Successful parents have successful kids. The reason, most parents assume, is that the winners had more help from mom and dad.

  Twin and adoption studies say almost the opposite. Successful parents may give their kids a small edge, but heredity is much more important. Kids literally inherit educational and financial success from their parents. The most influential gift that parents give their children is not money, connections, or help with their homework, but the right stuff.

  Parents have little effect on how much school their kids get. Parents feel an intense obligation to be involved with their kids’ education. Does their involvement yield fruit? Most twin and adoption studies respond, “slightly”; a few say, “yes, for earlier generations”; the rest give a flat-out “no.”

  In 1955, Harry Holt, an Oregon businessman, and his wife, Bertha, adopted eight Korean orphans. Soon they set up a charity to help other Americans adopt disadvantaged Koreans. The adopting families were unusually diverse. To be eligible, couples had to be married for at least three years, twenty-five to forty-five years old, with no more than four children, and a minimum income just 25 percent above the poverty line. In 2004–2005, economist Bruce Sacerdote tracked down over 1,600 of the Korean adoptees and their adopting families to see how they turned out.

  Nurture influenced the Koreans’ educational success. More educated moms and fewer siblings both helped—but only slightly. If the mother had an extra year of education, the child finished five extra weeks of education, and was 2 percentage points more likely to graduate from college. For every extra sibling, the adoptee finished six fewer weeks of education, and was 3 percentage points less likely to graduate from college.

  The Korean adoption study is most remarkable, though, for what it failed to find. Rich parents routinely try to give their kids an edge by moving to good school districts, hiring tutors, and paying tuition for fancy schools. Yet neither family income nor neighborhood income increased adoptees’ academic success. If you ever thought it unfair for rich parents to buy their children’s way through school, be at peace; apparently they don’t get what they pay for.

  Another major study of over 2,000 Swedish adoptees plus their adoptive and birth parents got almost the same results. The main difference: In Sweden, dads matter more, moms matter less. If the dad who raised you had one more year of education, you got five more weeks; if he finished college, you were 10 percentage points more likely to do the same. The only clear effect of maternal education, in contrast, was that kids were 10 percentage points more likely to finish college if their adopted moms did the same.

  Twin studies also find small effects of nurture on education. The most remarkable examined about 2,000 pairs of American twins who served in World War II, plus their grown children. The results? Genes matter a lot for educational success. If you’re more educated than four out of five people, you can expect your separated identical twin to be more educated than three out of four. Upbringing makes little difference. Only two nurture effects stand out in the veteran twins study. First, if your father is a professional or manager instead of an unskilled worker, you typically complete one more year of education. Second, every extra sibling depresses your educational achievement by seven weeks.

  Researchers who looked at about 2,500 Australian twins confirmed these results. Identical twins’ educational success is markedly more similar than fraternal twins’. Nurture does matter, but only slightly. If either parent gets an extra year of education, you get four or five extra weeks. If your family has an extra kid, you complete three fewer weeks.

  While twin and adoption studies usually find that your family has a small effect on how far you get in school, exceptions exist. Some twin research reports that upbringing used to be more important and continues to be more important for women. An early study of Norwegian twins found strong family effects for female twins born before 1961, and male twins born before 1940. During the prewar era, if you had one extra year of education, you could expect your adopted sibling to have about six extra months. Researchers using the Minnesota Twin Family Registry and the Finnish Twin Cohort Study similarly found moderate to large nurture effects for Americans and Finns born between 1936 and 1955.

  Other twin researchers conclude that children’s families have no long-run effect on educational success. Their reasoning: Husbands and wives don’t pair up randomly; married couples usually have similar levels of education, intelligence, and other genetically influenced traits. (The catch phrase is “assortative mating.”) The slightly yucky implication is that most of us are the fruit of mild incest. Since married couples are somewhat genetically similar, siblings share more than half their genes. Implication: Fraternal twins are genetically closer to identical twins than we thought, so standard twin methods underestimate nature and overestimate nurture.

 
When researchers fix this flaw, educational nurture effects go away. One team combined thousands of observations from earlier studies of spouses, parents, their children, siblings, and twins. After adjusting for spouses’ educational similarity, it found that family environment has no effect on how far you get in school. A more recent study of Australian twins reports moderate nurture effects on education, assuming people marry at random. Once the researchers discard this unrealistic assumption, nurture effects vanish for both men and women, even for those born in the first half of the twentieth century.

  Parents have no effect on grades. All of the twin and adoption studies we’ve seen so far focus on years of education and college graduation. When parents help with homework, though, maybe their goal is to help their kids learn more or get better grades. Do they succeed ? While this question has received less attention, the signs point to no. An early study of about 500 Australian twins reported little or no effect of upbringing on college-bound students’ knowledge of arts, science, English, geography, math, or biology. A research team investigating the attitudes of almost 700 Canadian twins discovered that family had no effect on high school seniors’ GPA.

  The most impressive evidence, however, comes from the U.S.based National Longitudinal Study of Adolescent Health, a nationally representative survey of seventh- through twelfth-graders living in the same household. The subjects were a mix of identical twins, fraternal twins, siblings, half siblings, cousins, and nonrelatives—about 1,700 kids in all. Genes had a strong effect on grades. If you’re in the 80th percentile of your class, expect the identical twin you’ve never met to be in the 71 st. Parental effects, in contrast, were literally invisible. The GPAs of unrelated kids raised together were no more similar than strangers’.

  The lesson: If you’ve ever felt angry about parents who do their kids’ homework for them, you can stop. In the long run, these parents aren’t inflating their kids’ grades. As far as we can tell, they’re either wasting their time or reliving their youth.

  Parents have little or no effect on how much money their kids make when they grow up. Most parents feel secondhand greed; or to be polite, they want their kids to be financially successful. True, more parents nag their kids to do well in school than to make a lot of money. Yet a lot of educational nagging is income nagging in disguise. Think about how parents react when their children choose a major. You want your kid to study medicine or law—not French poetry or sociology.

  Parents who want their kids to get ahead encourage education, but that’s only part of a bigger strategy. You’re also supposed to teach your child the value of a dollar, an honest day’s work, teamwork, initiative, and ambition. No matter what your income is, you’ve got something to stress about. If you don’t have money, you stress about the advantages you can’t give your children. How will they get ahead without the right connections? If you do have money, you stress about giving your kids too many advantages. If you spoil them, won’t it kill their drive and self-reliance?

  All this fretting is much ado about nothing. Yes, wealth and poverty run in families. According to twin and adoption studies, however, the main reason is not upbringing, but heredity. Nurture has even less effect on income than on education.

  In Sacerdote’s Korean adoption study, biological children from richer families grew up to have much higher incomes, but adoptees raised in the same families did not. The results are strong to the point of shocking. The income of the family you grew up with has literally no effect on your financial success. Korean adoptees raised by the poorest families have the same average income as adoptees raised by the richest families. While adoptees’ moms have a small effect on their education, that extra education fails to pay off in the job market. Growing up in a rich neighborhood is equally impotent. Small families boost kids’ incomes, but the effect is tiny: Every sibling depresses your adult income by about 4 percent. The Swedish adoption study mentioned earlier finds small effects on income rather than no effects at all. Being raised by a dad with 10 percent higher earnings causes you to earn 1 percent more when you grow up.

  Twin studies also find small to zero effects of nurture on financial success. Identical twins’ incomes are much more similar than fraternal twins’. A recent working paper looks at over 5,000 men from the Swedish Twin Registry born between 1926 and 1958. Identical twins turn out to be almost exactly twice as similar in labor incomes as fraternal twins—precisely what you would expect if family resemblance were purely hereditary. A study of over 2,000 Australian twins finds the same thing.

  Contrary evidence? In the U.S. Twinsburg Study, which looks at about 400 American male twins, nurture matters a bit more and nature matters a bit less. If you earn more than 80 percent of your peers, your adopted sibling can expect to earn more than 55 percent. A study of American full and half siblings using the National Longitudinal Survey of Youth (NLSY) implies an even more modest effect—the adopted sibling is expected to have a higher income than 53 percent of the population.

  You want your kids to succeed. But how much do you really help them? According to twin and adoption studies, not much. If your family is legally qualified to adopt, your parenting is good enough to allow your child to realize his potential. Whether he takes advantage of these opportunities is largely up to him.

  WISH #5: CHARACTER

  OK, so maybe I am lazy, but it’s not really my fault. I’ve been lazy ever since I was a little kid, and if some- one had caught it early on, maybe I wouldn’t be the way I am now.

  —Jeff Kinney, Diary of a Wimpy Kid: Dog Days

  “A Boy Named Sue” is one of Johnny Cash’s most famous songs—and certainly his funniest. In it, a deadbeat dad adds insult to injury. Before he abandons his son, he names him “Sue.”

  The name gives Sue a lifetime of grief, and he vows revenge. Years later, he finally bumps into his dad in a Gatlinburg bar. Father and son have a battle royal, then reach for their guns. The younger man’s a little quicker. Before Sue can commit patricide, however, his father reveals his true motive. He didn’t name him Sue out of cruelty. He did it to build his son’s character—and it worked:And he said, “Son, this world is rough, / And if a man’s gonna make it, he’s gotta be tough, / And I knew I wouldn’t be there to help ya along. / So I give ya that name and I said good-bye / I knew you’d have to get tough or die / And it’s the name that helped to make you strong.”

  Sue’s almost convinced. He spares his dad’s life, and calls him “Pa.” But he’s not convinced enough to put his own son through the same ordeal: “And if I ever have a son, I think I’m gonna name him . . . Bill or George, any damn thing but ‘Sue.’”

  Most parents aren’t as ruthless as Sue’s father, but his motive should be familiar. We want our children to grow up to be men and women of substance—of character. Like Sue’s dad, we want our children to be strong and determined, but that’s only the beginning. We also want our kids to be hardworking, diligent, honest, polite, cooperative, and kind—and we certainly don’t want them to become common criminals. If we have to occasionally hurt their feelings to raise them right, so be it.

  When you tell parents that they overestimate their influence, they often retreat to the bunker of character: “Maybe I can’t affect his IQ or his income, but I can control whether he grows up to be a decent person.” For health, intelligence, happiness, or success, most parents eventually learn some modesty. For character, they’re practically parental determinists: If you raise your children right, they will grow up to be good people—and if they turn out bad, the reason must be that you raised them wrong. Is there any truth to this? Is character a genuine exception to the rule that nurture doesn’t matter much?

  Parents have little or no effect on conscientiousness or agreeableness. To answer, we need plausible ways to measure character. Luckily for us, personality psychologists have been studying human personality for decades, so plausible measures of character already exist. According to most psychologists, personality traits fall under five big umbrella
s: openness, conscientiousness, extroversion, agreeableness, and neuroticism. If you make a list of the traits that almost all parents want to instill—hardworking, diligent, honest, polite, cooperative, kind, and so on—they fall under just two of the psychologists’ umbrellas: conscientiousness and agreeableness. One good way to test for parental influence on character is to use twin and adoption methods to figure out where conscientiousness and agreeableness come from.

  Personality psychologists have been there and done that. Some find small effects of family environment on character; the rest find none at all. Good kids do tend to come from good families. Yet contrary to what almost everyone thinks, the overarching reason is heredity, not upbringing. Sue had strength and determination because he inherited them from his strong-willed father, not because his girly name “made him strong.”

  Hillary Clinton outraged many people by insisting, “It takes a village to raise a child.” Her offense was not to deny the importance of parents but to hint that good parenting is not enough. The results from twin and adoption studies are more outrageous. You may be tempted to dismiss them out of hand. But before you do, how about a tour of the evidence?