The kids will turn out alright, even if you don’t break an arm and a leg trying to raise them. According to Dr. Bryan Caplan at George Mason University, too many parents are “overcharging themselves emotionally,” because they’re convinced that nurture plays a strong role in how the kids will turn out. Twin research shows however that nature seems to be the far more influential factor in determining  the characteristics today’s children exhibit as adults.

The most prominent conclusion of twin research is that practically everything-health, intelligence, happiness, success, personality, values, interests-is partly genetic. The evidence is straightforward: Identical twins are more similar than fraternal twins in almost every way-even when the twins are separated at birth. But twin research has another far more amazing lesson: With a few exceptions, the effect of parenting on adult outcomes ranges from small to zero.Parents change kids in many ways; the catch is that the changes fade out as kids grow up.  By adulthood, identical twins aren’t slightly more similar than fraternal twins; they’re much more similar.  And when identical twins are raised apart, they’re often just as similar as they are when they’re raised together.

Once I became a dad, I noticed that parents around me had a different take on the power of nurture. I saw them turning parenthood into a chore-shuttling their kids to activities even the kids didn’t enjoy, forbidding television, desperately trying to make their babies eat another spoonful of vegetables. Parents’ main rationale is that their effort is an investment in their children’s future; they’re sacrificing now to turn their kids into healthy, smart, successful, well-adjusted adults.  But according to decades of twin research, their rationale is just, well, wrong.  High-strung parenting isn’t dangerous, but it does make being a parent a lot more work and less fun than it has to be.

The obvious lesson to draw is that parents should lighten up.  I call it “Serenity Parenting”: Parents need the serenity to accept the things they cannot change, the courage to change the things they can, and (thank you twin research) the wisdom to know the difference.  Focus on enjoying your journey with your child, instead of trying to control his destination. Accept that your child’s future depends mostly on him, not your sacrifices. Realize that the point of discipline is to make your kid treat the people around him decently-not to mold him into a better adult.  I can’t say that I completely convinced my wife on any of these points, but we made reasonable compromises-and we found that raising twins was a lot of fun.

I remember when Dr. Caplan first discussed his book Selfish Reasons to Have More Kids when it was still in the making and thinking how intriguing his insights were. His arguments certainly lend justification to a balanced approach to parenting and take the wind out of Tiger Mom’s sails.