What Your Child's DNA Can Tell You About Parenting

DNA discoveries are revealing why even the best parenting doesn't have the effects experts promise, from breast-feeding to letting kids learn from mistakes.

If there is one thing experts on child development agree on, it is that kids learn best when they are allowed to make mistakes and feel the consequences. So Mom and Dad hold back as their toddler tries again and again to cram a round peg into a square hole. They feel her pain as playmates shun her for being pushy, hoping she'll learn to back off. They let their teen stay up too late before a test, hoping a dismal grade will teach her to get a good night's sleep but believing that ordering her to get to bed right now will not: kids who experience setbacks rather than having them short-circuited by a controlling parent learn not to repeat the dumb behavior.

But not, it seems, all kids. In about 30 percent, the coils of their DNA carry a glitch, one that leaves their brains with few dopamine receptors, molecules that act as docking ports for one of the neurochemicals that carry our thoughts and emotions. A paucity of dopamine receptors is linked to an inability to avoid self-destructive behavior such as illicit drug use. But the effects spill beyond such extremes. Children with the genetic variant are unable to learn from mistakes. No matter how many tests they blow by partying the night before, the lesson just doesn't sink in.

The discovery, reported last December, is part of what is fast becoming the newest frontier in studies of why children turn out as they do. Since the first advice book for American parents appeared in 1811, the child-rearing industry, as well as researchers who have made child development a science, have assumed that, although every child is an individual, there are certain universals. If parents are too take-charge about homework, the child becomes disengaged and eventually gives up; if they are warm and affectionate, kids don't act out. But while most children do respond the way research shows, there have always been "outliers," kids who don't turn out the way experts promise.

Research showing that the most scientifically rigorous child-rearing advice can blow up on you couldn't come at a worse time for the millions of American parents who are desperate for direction. They are gobbling up how-to books and DVDs, even hiring coaches and consultants. They are tearing their hair out over conflicting advice on even such basics as sleep—let baby cry herself to sleep? Co-sleep? (As it turns out, the conflicting advice may reflect the fact that the "experts' " experience happens to have been with children whose genetic disposition is amenable to their way of doing things.) More than earlier generations, new parents are panicked that they're going to screw up. That feeling is fed by posts on Web sites such as UrbanBaby, in which someone, somewhere, can be counted on to flame your every parenting decision. But for parents who look back in sadness—perplexed that although they did everything "right," their child is not as kind, or intelligent, or self-confident, or well adjusted as the recipes promised—the emerging science offers an explanation, and perhaps an out: with the DNA stacked against you, it wasn't your fault.

One of the strongest and most counterintuitive findings in this nascent field is that children with a sweet temperament, which is under strong genetic control, are the least likely to emulate their parents and absorb the lessons they teach, while fussy kids are the most likely to do so. Fussy children have a hypersensitive nervous system that is keenly attuned to its surroundings—including what Mom and Dad do and say. In studies that are shaking up textbook dogmas, Jay Belsky of Birkbeck University of London has shown that fussy babies are therefore wired to be more strongly shaped by their parents than mellower children are. It is the fussy baby who, read to night after dutiful night, is likely to develop a love of books; the mellow baby, given the same literary diet, might just as easily grow into a teen who has no interest in reading anything longer than a text message. The mellow baby, immune to your charms, is more likely to show signs of road rage from the day she first takes her tricycle out for a spin, even though she grew up watching your saintly temper control. Children who go with the flow of new people and new situations are like Teflon: good parenting doesn't stick to them—but neither, necessarily, does bad parenting. They're the young adults who can't form close, meaningful relationships despite the unconditional love you showed them. "Kids with difficult temperaments are more sensitive to the effects of parenting," says Belsky. "You can get by with sloppier parenting if you have a 'good temperament' kid." Even children who fall between the extremes are generally closer to one than the other.

Although whether you have an easy or a fussy child is obvious, other innate differences that shape whether and how a child will respond to how parents raise them are less apparent. But since they reflect the presence of a DNA variant, they are all candidates for being pinpointed with a genetic test that will help parents know what to expect:

孩子的DNA反映家教知多少

我做的每件事都是恰当的。

DNA的研究表明之所以最好的家庭教育没有取得如专家们所希望的效果，原因在于从喂奶到教孩子从错误中吸取经验教训等方方面面都没有做好。

要说在“育儿方面”专家们还有一点共同看法的话，那就是大家都认为允许孩子犯错，并让他们体验到后果，这样孩子才能学得最好。所以爸爸妈妈们在他们蹒跚学步的孩子试图把圆圆的钉子往方形的孔里塞的时候，什么也别管就行了。当孩子的玩伴们因为她爱出风头离她而去是，父母们会感受到她的苦痛的，并且希望她学会收敛一些。他们让他们十几岁的孩子考试前开夜车学习，就是希望糟糕的成绩会教他去睡个好觉并且坚信命令她去睡觉不起作用。只有经历过挫折的孩子而不是被控制性的父母控制的四处“短路”的孩子才能学会不再重犯愚蠢的错误。

但，看来，并非所有的孩子如此。在大约百份之三十的孩子当中，他们的DNA螺旋结构中有一个给他们的脑子留下多巴胺的缺失，该分子起的作用是存放控制我们的思维与意识的某一种影响神经系统的化学物质。多巴胺的缺失是与一种诸如使用违禁药品等不由自主的自残行为有关。但影响并非那么糟糕透顶。有遗传性变异的孩子不能从经验中汲取教训。不管他们头天晚上经过了多少次预先安排的测试，教训总记不住。

去年十二月公布的该项研究很快成为为何孩子们“各有所出，全由天赋”一系列研究的一部分。自1811年第一本给美国家长们的育儿建议书出现后，育儿从业人员还有把儿童发展当成一门科学来研究的专家们已经预计到：虽然各个儿童是一个个体，但有共同点。如果家长们对家庭作业管得太少的话，孩子会变得懒散起来，最后干脆放弃。如果他们很热情很关注的话，孩子就不会当面一套，背后一套。虽然绝大部分孩子的反映和研究结果吻合，但总有“偏离者”那些孩子的反映与专家们的期望大相径庭。

忽略那些孩子数年之后，有几位科学家现在意识到他们正向我们讲述一些事例，这些事例有望给我们对儿童发展的理解带来颠覆性的观点。作为对“个性化医疗”的回应（指根据各人的DNA配药），科学家们发现父母对待孩子的方式经过了DNA三棱镜的过滤。父母们可能直觉上知道那一点，因为他们发现在一个孩子身上发生的事情可能不会在另一个孩子身上发生，令人琢磨不透。但现在的科学能精确地指出先天因素和后天营养供应短缺造成的共同结果。专家们终于涣然大晤原来“