A similar argument can be applied to the notion held by our society that having better or lesser verbal skills and reading skills is a function of innate verbal ability. To a parent, these skills seem seem innate, because from the moment their daughter could talk, she was precocious-speaking full sentences by two, reading words by three and books by four. But the parent's unaware of his own influence in those first two years. innate, because from the moment their daughter could talk, she was precocious-speaking full sentences by two, reading words by three and books by four. But the parent's unaware of his own influence in those first two years.

"When parents see development in their kids, they are only seeing the output-not the mechanisms underneath," said Goldstein. "We just see significant changes, so parents tend to say, 'It must be built in.' I don't think people are aware of what they are bringing to babies."

According to an extensive study comparing identical twins to fraternal twins, headed by University of New Mexico's Dr. Philip Dale, only 25% of language acquisition is due to genetic factors.

So do kids who get a head start keep their advantage, over time? Does being an early talker really mean the child will be a better reader, in elementary school? Or do other kids quickly catch up, once they hit the language spurt, too?

Scientists tend to say that both both are true. The advantage is real, yet many kids do catch up, and show no long-term consequences. Dr. Bruce Tomblin, Director of the Child Language Research Center at the University of Iowa, noted that language measures are highly stable once children are in elementary school, but prior to that age, they're not stable. "The trajectories of their future results look like spaghetti," he said. "The only thing typical about typical language development was variability." are true. The advantage is real, yet many kids do catch up, and show no long-term consequences. Dr. Bruce Tomblin, Director of the Child Language Research Center at the University of Iowa, noted that language measures are highly stable once children are in elementary school, but prior to that age, they're not stable. "The trajectories of their future results look like spaghetti," he said. "The only thing typical about typical language development was variability."

According to Tamis-LeMonda, this is especially true for toddlers who spoke late, but still understood a lot of words early. "Sometimes a kid who seems to catch up wasn't actually behind in the first place; their receptive vocabulary was proceeding apace, but they weren't talking much because they were shy or didn't quite have the motor control yet."

Harvard University's Dr. Jesse Snedeker has studied how international adoptees fare in the United States. These children often spend their first year, or years, in orphanages and with foster families, then come to American families that are quite well-off. Some adoptees do have learning difficulties, but "the adoptees who were typically developing... they caught up to their American-born peers within three years," concluded Snedeker. This was true whether they were adopted at age one or age five-even up to age ten.

Nevertheless, the general trend is apparent: an early advantage in language can be quite meaningful, at least through the first several years of elementary school. Going back to the famous Hart and Risley study from the University of Kansas, Dr. Dale Walker a.n.a.lyzed how those children were doing academically six years later-in third grade, at age nine. The measures taken at age three, of how long kids' average spoken sentences were, and how big their spoken vocabulary was, strongly predicted third-grade language skills. The correlation was strongest for their spoken language ability, and it was still quite strong for their reading, spelling, and other measures of verbal ability. It didn't help with math, which wasn't a surprise; presumably, this head start in language wouldn't drive all cognitive functions.

It's important to characterize early language precocity for what it is: a head start, but far from a guarantee. "It's not like the infancy period is the only critical period," said Tamis-LeMonda. "New skills are emerging in every period, and vocabulary development has to continually expand."

ConclusionThe Myth of the Supertrait.

When Ashley and I began this book, we adamantly chose not to focus just on children's intellectual prowess. Brainy prodigies were not our goal; rather, we were interested in a more complete perspective of children, including the development of their moral compa.s.ses, their behavior around peers, their self-control, and their honesty.

We chose this subject at what seemed a fortuitous time. Over the last ten years, a new branch of psychology has emerged. Rather than studying clinical patients with pathologies, these scientists have applied their skills to studying healthy, happy people who thrive, in order to discern what were the habits, values, and neuroscience of those with greater well-being. This new starting-point has led to insights about the strengthening of positive emotions such as resilience, happiness, and grat.i.tude.

In one celebrated example, Dr. Robert Emmons, of the University of California at Davis, asked college students to keep a grat.i.tude journal-over ten weeks, the undergrads listed five things that had happened in the last week which they were thankful for. The results were surprisingly powerful-the students who kept the grat.i.tude journal were 25% happier, were more optimistic about the future, and got sick less often during the controlled trial. They even got more exercise.

Emmons repeated his study, this time with undergrads writing in a grat.i.tude journal every day for two weeks-and he also sent questionnaires about the partic.i.p.ants to their close friends, asking them to rate their friend on a variety of measures. He wanted to see if the subjects' improved sense of well-being was more than just an internal state of mind; did it actually affect how they interacted with others? The answer was a confident yes. Their friends had noticed them being more helpful and emotionally supportive.

Philosophers have long written about the importance of grat.i.tude. Cicero called it the parent of all other virtues. Shakespeare described ingrat.i.tude as a marble-hearted fiend, and he decried ingrat.i.tude in children as being more hideous than a sea monster. But until Emmons' research, we couldn't really say whether grat.i.tude triggered well-being, or whether grat.i.tude was merely the by-product of well-being. Certainly the two rise and fall together, but Emmons showed that grat.i.tude could be enhanced, independently, and greater well-being would result.

By itself, this wasn't exactly extraordinary, but in the context of happiness theories, it was significant. Back in 1971, two scholars, Philip Brickman and Donald Campbell, described the human condition as a "hedonic treadmill." Essentially, we have to keep working hard just to stay in the same relative place in society. Even when our situation improves, the sense of achievement is only temporary, because our hedonistic desires and expectations rise at the same rate as our circ.u.mstances. Brickman and Campbell noted that lottery winners are not any happier, long-term, than non-winners, and paraplegics are not less happy than those of us with all our limbs. They argued that this plight was inescapable, due to our neural wiring. Our brains are designed to notice novel stimuli, and tune out everyday, predictable stimuli. What we really notice, and are affected by, are relative and recent changes. As soon as those become static, we return to a baseline level of well-being.

That we are so adaptive can be a good thing. When life falls apart, we'll soon get used to it-such changes in circ.u.mstance don't have to become incapacitating. But when our lives are blessed, and things are going well, there seems something morally decrepit in how we so easily overlook how good we have it.

In the last forty years, a lot of cracks have been discovered in Brickman and Campbell's theory of the hedonic treadmill. First, while most people might have a happiness set point, it's not a flat neutral-it's actually a fairly positive state. Around the world, 80 percent of people report being quite happy or very happy. Also, while paraplegics and lottery winners might return to their baseline, other cla.s.ses of people (on average) never quite recover-such as widows, divorcees, and the long-term unemployed.

Emmons' work was yet another crack in the hedonic treadmill theory. Effectively, he demonstrated that our default wiring can be consciously tricked; by forcing college students to pay attention to the bounty in their everyday lives, he got them to escape the perception-trap of the treadmill.

One of the many scholars inspired by Emmons' research was Dr. Jeffrey Froh, a psychology professor at Hofstra University on Long Island. Froh also served as the psychologist for the Half Hollow Hills school district, spending a fair amount of time in the local grammar schools and high schools. Froh had been struck by the rampant materialism and sense of ent.i.tlement within the affluent Long Island youth culture.

"At the high school, there were BMWs in the parking lot, and E-Cla.s.s Mercedes," Froh said. "And they really wanted to look a certain way. They dressed immaculate. They wore two-hundred-dollar jeans, and hundred-dollar T-shirts. They wanted peers to know they didn't get these on sale, and they weren't knockoffs. There was also a lot of focus on where they'd been admitted to college-not for the educational value, but for the status and prestige, for the name brand of certain universities."

He saw in Emmons' work a possible antidote to all that.

Froh certainly wasn't alone in that view. Educational inst.i.tutes, newspaper columnists, and parenting coaches began advocating that children keep grat.i.tude journals. Many schools started incorporating grat.i.tude exercises into their curricula.

Froh, however, thought these efforts warranted scientific testing and real a.n.a.lysis. So with Emmons' consultation, Froh began the first randomly a.s.signed, controlled trial of grat.i.tude in schoolchildren.

Hoping to help these kids before they turned into materialistic high schoolers, he went into the Candlewood Middle School in Dix Hills, New York, and enlisted the cooperation of the three teachers who taught "Family and Consumer Science" to sixth and seventh graders. All told, eleven cla.s.srooms were involved, amounting to 221 students; this included a cross-section of the whole school, with some gifted children and special education children. Four of the cla.s.ses were given grat.i.tude journals; daily, for two weeks, the students were asked to "think back over the last day and write down on the lines below up to five things in your life that you are grateful for or thankful for."

This took just a few minutes at the start of each cla.s.s. Some responses were quite specific ("I am grateful my mom didn't go crazy when I accidentally broke a patio table"); some hinted at a specific event but didn't explain it in detail ("My coach helped me out at baseball practice"); far more were all-encompa.s.sing ("My grandma is in good health, my family is still together, my family still loves each other, and we have fun every day"). Froh was particularly excited by how few of the kids' items had anything to do with their possessions. Very little materialism emerged, and even then, it was eccentric, such as the child who was grateful for all the Star Wars Star Wars books. The grat.i.tude inventories, it seemed, were recalibrating the kids' focus. books. The grat.i.tude inventories, it seemed, were recalibrating the kids' focus.

Before, during, and after the two-week period, teachers also pa.s.sed out and collected questionnaires that measured students' life satisfaction, grat.i.tude, and emotions. This was repeated three weeks later, to see if the benefits lasted. The teachers were never told the purpose of the study, so they couldn't bias the results; for the most part, they stuck to scripts Froh had written.

At the same time, three cla.s.srooms were a.s.signed as control groups; all these students did were the questionnaires, with no other writing. The last four cla.s.ses were instructed to complete the questionnaires, and also to complete their own daily writing a.s.signment: the students in these cla.s.ses listed five ha.s.sles that had occurred each day. Froh considered these four cla.s.ses as a kind of alternative control group, to check for effects of dwelling on the negative.

So what was the impact of counting blessings?

There was none.

The four cla.s.ses of students who counted their blessings didn't experience more grat.i.tude than the control group-not during the two-week exercise, immediately after, or three weeks later. The journal writing simply didn't have the intended effect. At all stages, the three cla.s.ses in the control group-which did nothing but take the mood questionnaires-experienced the most grat.i.tude of the three groups. As a result, the kids who did the exercise weren't friendlier or more helpful to their friends. They didn't have greater all-around life satisfaction.

Strangely, though, these lackl.u.s.ter results didn't slow down the excitement around Froh's study. The grat.i.tude journal sounded like exactly the sort of exercise kids should should do. Everyone involved wanted it to work and fully expected it to work. With that kind of momentum built up, everyone was predisposed to consider the intervention a success, no matter what the data determined. do. Everyone involved wanted it to work and fully expected it to work. With that kind of momentum built up, everyone was predisposed to consider the intervention a success, no matter what the data determined.

The study results were published in a notable journal. Candlewood Middle School itself was so happy with the exercise that the administrators had all the thousand-plus students repeat it.

Newspapers then wrote feature stories about Froh's study, clearly creating the impression that his study had effectively reproduced the results of Emmons' studies on college students. In none of the articles was there a single mention about the flimsiness of the results. A year later, when Thanksgiving rolled around again-triggering a new round of coverage-these same claims were repeated.

One explanation for the press accounts could be the distraction created by the data on the alternative control group-the four cla.s.ses who dwelled on the negative every day. Not surprisingly, those kids looked a little worse, statistically, than the other groups. But there was scant evidence that writing in the grat.i.tude journal improved one's well-being more than doing nothing. The only thing the study proved was that dwelling on the negative can b.u.m you out.

Why were the results so different from Emmons' work on college students?

Froh wasn't sure, and he was troubled. He set the quant.i.tative a.n.a.lysis aside, to go reread the kids' actual diary entries. Quickly, he realized that a fair number of the middle schoolers suffered grat.i.tude fatigue.

"They wrote the same thing, day after day-'my dog, my house, my family,' " Froh recalled. "In hindsight, it might have been ideal for the teachers to encourage the kids to vary their answers, think harder, and really process it-rather than let them complete it in a hurry so they could get back to their cla.s.swork."

He realized his next experiment would have to address this.

At first glance, Froh's study appears to be another cla.s.sic case where good intentions were mistaken for a good idea. But his story didn't end there.

For Froh to really figure out what happened, he needed to drop two of his main a.s.sumptions.

First, he had to drop his expectation that middle schoolers should react the same way as college students to the grat.i.tude intervention. As long as he held that expectation, he was thinking that something had gone wrong in his study-and that if he could find his error, he could get the intended result.

But maybe nothing had gone wrong. Maybe he'd made no mistakes, and his results were completely accurate. And because he wasn't thinking broadly enough, he was unable to glean what his results actually proved.

There are eight years of development from middle school to college. Was there something about those intervening years that could explain why the middle-schoolers didn't benefit from the exercise? As we learned from Nancy Darling's research on teenagers, the need for autonomy peaks at age 14, and is stronger in a 12-year-old than in a college student (largely because a college student has already established the autonomy she desires). Were the middle-schoolers reacting differently, because of their need for independence?

Or could it be a difference in cognitive capabilities? Digging deeper into grat.i.tude's effects, Froh learned that children will not experience grat.i.tude unless they recognize three things about the various bounties in their lives: that they are intentional, costly, intentional, costly, and and beneficial. beneficial. Children need to comprehend that this nice life of theirs isn't by accident, it's the gift of hardworking parents and teachers who make sacrifices for the good of children-who in turn truly benefit from it. Children need to comprehend that this nice life of theirs isn't by accident, it's the gift of hardworking parents and teachers who make sacrifices for the good of children-who in turn truly benefit from it.

Were younger kids capable of understanding all that?

Froh began to design a new study, working with a K12 parochial school, where he could test a grat.i.tude intervention on kids from grades 3, 8, and 12, to look for the effects of age.

That Froh had chosen a parochial school was an interesting choice. The school's religious teachings on sacrifice could have already given its students an increased awareness of grat.i.tude. Froh knew that these kids were already regularly taught to count their blessings in the context of prayer.

To give them something new, Froh didn't ask these children to list five things every day. Instead, they were to pick one person in their lives-someone they'd never fully expressed their appreciation for-and write them a letter of thanks. They worked on this letter in cla.s.s, three times a week, for two weeks, elaborating on their feelings and polishing their prose. On the final Friday, they were to set up a time with that person and read the letter to them, out loud, face-to-face.

Their letters were heartbreaking and sincere, demonstrating a depth of thoughtfulness not seen in the previous study. "It was a hyperemotional exercise for them," Froh said. "Really, it was such an intense experience. Every time I reread those letters, I choke up."

But when Froh a.n.a.lyzed the data, again he ran into the same problem-overall, the kids hadn't benefited from the intervention. What was going on?

To solve it, Froh had to extract himself from another a.s.sumption.

He'd a.s.sumed that positive emotions, like grat.i.tude, are inherently protective-they ward off problem behavior and prevent troubled moods. He wasn't alone in this a.s.sumption; in fact, it is the core premise of every scholar working in the field of positive psychology.

Because of this, Froh had expected to find an inverse relationship between grat.i.tude and negative emotions, such as distress, shame, nervousness, hostility, and fear. Meaning, even if he couldn't change the amount of kids' grat.i.tude the way Emmons had, Froh still expected that some kids would feel a lot of grat.i.tude, and others less or none at all. And he figured that kids who felt very grateful and appreciative would be spared from the brunt of troubled moods. It should protect them. But the data from his multiple studies didn't support this. Kids high in grat.i.tude suffered storms of emotion just as commonly as the kids low in grat.i.tude.

At that point, Froh's thinking was sparked by a few scholars who were rethinking the hedonic treadmill.

"They argued that happiness is not a unitary construct," Froh explained. "You can feel good and have well-being, but still be nervous, still be stressed. You can feel better overall, but the daily stressors haven't necessarily gone away. For a scholar, this means that when you measure for positive affect, negative affect, and life satisfaction, they won't all move in the same direction."

Froh looked very carefully at each band of data measuring the kids' emotions during the second study. Overall, writing the thank-you letters had little benefit, just like his prior study. But this aggregation masked what was really going on. It turned out that some kids were were benefiting from the exercise, while others weren't. Together, their scores canceled each other out. benefiting from the exercise, while others weren't. Together, their scores canceled each other out.

Those who benefited from the exercise were kids low in positive affect-kids who rarely experienced emotions like excitement, hope, strength, interest, and inspiration. Writing the thank-you letter, and presenting it to a parent, coach, or friend, did indeed fill them with grat.i.tude and make them feel better about their lives. "Those are the kids who would really benefit from grat.i.tude exercises," said Froh. "The children who usually appear unengaged, or not very alert. They're rarely cheerful or content."

However-and this is the important twist-for those kids who normally experienced a lot of hope and excitement, Froh's exercise had the opposite outcome. It made them feel less happy, hopeful, and grateful.

Why was the grat.i.tude exercise making them feel worse? worse? What could possibly be What could possibly be bad bad about grat.i.tude? about grat.i.tude?

Well, for kids with a strong need for autonomy and independence, it might be demoralizing to recognize how much they are dependent upon grownups. They might already feel like adults are pulling all the strings in their lives-controlling what they eat, what they study, what they're allowed to wear, and who they hang out with. And they'd rather feel self-reliant than beholden. Their sense of independence might be an illusion, but it's a necessary illusion for their psychological balance and future growth into genuine independence. Their lack of grat.i.tude might be the way they maintain the illusion that they are in control of their own lives.

Froh is considering that his intervention led those children to realize just how much of their lives depended on someone else's whim or sacrifice. They didn't feel happy that people were always there doing things for them. Instead, it made them feel powerless.

The lesson of Jeffrey Froh's work is not not that society should simply give up on teaching children about grat.i.tude. Certainly, some children do benefit from the exercises. (In fact, Froh remains so committed to the idea that one of his grad students recently began pilot-testing a five-week grat.i.tude school curriculum.) However, for most kids, grat.i.tude is not easily manufactured, and we can't take it for granted that grat.i.tude should supersede other psychological needs just because we want it to. that society should simply give up on teaching children about grat.i.tude. Certainly, some children do benefit from the exercises. (In fact, Froh remains so committed to the idea that one of his grad students recently began pilot-testing a five-week grat.i.tude school curriculum.) However, for most kids, grat.i.tude is not easily manufactured, and we can't take it for granted that grat.i.tude should supersede other psychological needs just because we want it to.

The real value in Froh's story, however, isn't limited to his insight on grat.i.tude. We're including it here because we think that his entire process is also ill.u.s.trative of a much larger point.

When we looked back at all the enormity of research that this book was built on, an interesting pattern was apparent. Most of the noteworthy insights into child development were revealed when scholars dropped the same two a.s.sumptions as Froh had.

Or, to restate that with more emphasis: a treasure trove of wisdom about children is there for the grasping after one lets go of those two common a.s.sumptions.

The first a.s.sumption is that things work in children in the same way that they work in adults. To put a name to this reference bias, let's call it the Fallacy of Similar Effect.

In chapter after chapter of this book, great insights were gained when scholars set that a.s.sumption aside. Consider the research into sleep. It was, for a long time, all too convenient to a.s.sume kids are affected by sleep loss the same way as adults-it's tiring but manageable. But when scholars decided to test that, they found that the magnitude of effect on kids was exponentially damaging.

In the same way, we presumed that because measured intelligence is stable in adults, it's also stable in young children. It's not-it plateaus and spurts. And because adults can pick up the implicit message of multiculturally diverse environments, we a.s.sumed kids can, too. They can't-they need to hear explicit statements about how wrong it is to judge people for their skin color.

Here's yet another example of this fallacy in operation. In our chapter about Tools of the Mind, we described how pretend play is the way young kids master symbolic representation, which soon becomes necessary for all academic coursework. But this crucial point never comes up when society debates the purpose of kids' free time, or the necessity of school recess. Instead, the arguments are always about exercise and social skills. That's because for adults, playtime is a chance to blow off steam and relax with friends. While those are certainly relevant to children too, our adult frame of reference has caused us to overlook a crucial purpose of play.

The Fallacy of Similar Effect also helps explain why society got it wrong on praising children. In a variety of studies, praise has been shown to be effective on adults in workplaces. Grownups like being praised. While praise can undermine a child's intrinsic motivation, it doesn't have this affect on adults. It has the opposite effect: being praised by managers increases increases an adult's intrinsic motivation, especially in white-collar professional settings. (Only in a few circ.u.mstances, such as some blue-collar union workplaces, is praise interpreted as untrustworthy and manipulative.) It's because we like praise so much that we intuited lavishing it upon kids would be beneficial. an adult's intrinsic motivation, especially in white-collar professional settings. (Only in a few circ.u.mstances, such as some blue-collar union workplaces, is praise interpreted as untrustworthy and manipulative.) It's because we like praise so much that we intuited lavishing it upon kids would be beneficial.

The second a.s.sumption to drop, as ill.u.s.trated in Froh's story, is that positive traits necessarily oppose and ward off negative behavior in children. To name this bias, let's call it the Fallacy of the Good/Bad Dichotomy.

The tendency to categorize things as either good for children or bad for children pervades our society. We tend to think that good behavior, positive emotions, and good outcomes are a package deal: together, the good things will protect a child from all the bad behaviors and negative emotions, such as stealing, feeling bored or distressed, excluding others, early s.e.xual activity, and succ.u.mbing to peer pressure.

When Ashley and I first began this book, we wrote out a wish list of Supertraits we wanted for kids-grat.i.tude, honesty, empathy, fairness. If we could sufficiently arm children with Supertraits such as these, we hoped that problems would bounce off them just as easily as bullets bounced off Superman.

Then Victoria Talwar taught that us that a child's dishonesty was a sign of intelligence and social savvy. Nancy Darling explained how teens' deception was almost a necessary part of developing one's adolescent ident.i.ty. Laurie Kramer's research showed us how blind devotion to fairness can derail sibling relationships. Patricia Hawley and Antonius Cillessen revealed how empathy may be evil's best tool: the popular kids are the ones who are the best at reading their friends-and using that perception for their gain. And of course, there was that study about imprisoned felons having higher emotional intelligence than the population as a whole.

It isn't as if we've now abandoned our desire for children to acquire honesty and other virtues. (And we're still telling kids to "play nice" and say thank you.) But we no longer think of them as Supertraits-moral Kevlar.

The researchers are concluding that the good stuff and the bad stuff are not opposite ends of a single spectrum. Instead, they are each their own spectrum. They are what's termed orthogonal-mutually independent.

Because of this, kids can seem to be walking contradictions. A child can run high in positive emotions and and high in negative emotions-so the fact that a teen can be happy about a new boyfriend won't negate her stress over school. There can be wild disconnects between children's stated opinions and their actions. Kids can know that fruit tastes good and that it's good for them-but that doesn't mean kids will eat any more apples. high in negative emotions-so the fact that a teen can be happy about a new boyfriend won't negate her stress over school. There can be wild disconnects between children's stated opinions and their actions. Kids can know that fruit tastes good and that it's good for them-but that doesn't mean kids will eat any more apples.

And many factors in their lives-such as sibling interactions, peer pressure, marital conflict, or even grat.i.tude-can be both a good influence and and a bad influence. a bad influence.

Despite these contradictions, the goal of having a deeper understanding of children is not futile. In fact, it's by studying these apparent contradictions very closely that deeper understanding emerges.

It's when children are at their most mysterious that we, their caretakers, can learn something new.

ACKNOWLEDGMENTS.

We wish to thank Adam Moss and Hugo Lindgren at New York Magazine New York Magazine for encouraging us to "geek out" in our stories, trusting that readers would be turned on, not turned off, by the depth of science we covered. Many others at for encouraging us to "geek out" in our stories, trusting that readers would be turned on, not turned off, by the depth of science we covered. Many others at New York New York also deserve credit-especially Lauren Starke, Serena Torrey, and our former editor, Adam Fisher. also deserve credit-especially Lauren Starke, Serena Torrey, and our former editor, Adam Fisher.

At our publisher, Twelve, special thanks go to Jon Karp, Jamie Raab, and Cary Goldstein. Peter Ginsberg, at Curtis Brown Ltd., played a huge role in guiding us. We are also indebted to Nathan Bransford, Shirley Stewart, and Dave Barbor.

Of course, we're enormously grateful to many scholars and others who were instrumental in helping us with our research. Our praise chapter-the catalyst for our first piece for New York New York on the science of kids-would not have been possible without the cooperation of Stanford University's Carol S. Dweck. Our chapter on "Why Kids Lie" just wouldn't have been the same without the cooperation of McGill University's Victoria Talwar and her entire lab-especially Cindy M. Arruda, Simone Muir, and Sarah-Jane Renaud. Similarly, our language chapter is particularly indebted to Michael H. Goldstein and Jennifer A. Schwade of Cornell University and the rest of the B.A.B.Y. Lab. Deborah J. Leong, Elena Bodrova, and Amy Hornbeck showed us Tools of the Mind in action. University of Illinois at Urbana-Champaign's Laurie Kramer and Mary Lynn Fletcher spent snowy days driving us around, while explaining their work on sibling relationships. We are also indebted to the many families who spoke with us and allowed us to observe their children's partic.i.p.ation in lab experiments. on the science of kids-would not have been possible without the cooperation of Stanford University's Carol S. Dweck. Our chapter on "Why Kids Lie" just wouldn't have been the same without the cooperation of McGill University's Victoria Talwar and her entire lab-especially Cindy M. Arruda, Simone Muir, and Sarah-Jane Renaud. Similarly, our language chapter is particularly indebted to Michael H. Goldstein and Jennifer A. Schwade of Cornell University and the rest of the B.A.B.Y. Lab. Deborah J. Leong, Elena Bodrova, and Amy Hornbeck showed us Tools of the Mind in action. University of Illinois at Urbana-Champaign's Laurie Kramer and Mary Lynn Fletcher spent snowy days driving us around, while explaining their work on sibling relationships. We are also indebted to the many families who spoke with us and allowed us to observe their children's partic.i.p.ation in lab experiments.

Dozens of researchers kindly agreed to be interviewed. Countless others sent advanced drafts of papers and presentations. We hounded scholars at conferences. We made pests of ourselves with endless rounds of e-mails and so sorry to call again but if you could clarify that number just one more time.... Despite all that, they were uniformly gracious.

Thanks to Brown University's Mary A. Carskadon, Judith Owens, and Monique K. LeBourgeois; Douglas K. Detterman at Case Western Reserve University; and, also at Cornell University, B.J. Casey, Marianella Casasola, Gary W. Evans, Jeffrey T. Hanc.o.c.k, and Heidi R. Waterfall; Columbia University's Jeanne Brooks-Gunn and Geraldine Downey; at Duke University, Kenneth A. Dodge, Jennifer E. Lansford, and James Moody; Florida State University's Roy F. Baumeister and Stephen I. Pfeiffer; David S. Crystal, Georgetown University; Harvard University's Mahzarin R. Banaji, Kurt W. Fischer, and Jesse Snedeker; Linda B. Smith, Indiana University; Douglas A. Gentile of Iowa State University; Cynthia L. Scheibe of Ithaca College; Kent State University's A. Margaret Pevec and Rhonda A. Richardson; Robert D. Laird, Louisiana State University; Kay Bussey, Macquarie University; Dan Ariely at Ma.s.sachusetts Inst.i.tute of Technology; Judith S. Brook and Catherine S. Tamis-LeMonda of New York University; Northwestern University's Frederick W. Turek; Oberlin College's Nancy Darling; Christopher Daddis and Sarah J. Schoppe-Sullivan of Ohio State University; Jeane Coperhaven-Johnson of Ohio State University at Mansfield; Marjorie Taylor, University of Oregon; Duane F. Alwin, Clancy Blair, Linda L. Caldwell, Pamela M. Cole, and Douglas M. Teti of Pennsylvania State University; Shawn Whiteman at Purdue University; Rutgers University's W. Steven Barnett; Jean M. Twenge, San Diego State University; Jamie M. Ostrov, State University of New York, University at Buffalo; Tabitha R. Holmes at State University of New York, New Paltz; Avi Sadeh at Tel Aviv University; Texas A&M University's Cecil R. Reynolds; Birgitte Vittrup, Texas Women's University; Laurence Steinberg at Tufts University; Noel A. Card and Stephen T. Russell of the University of Arizona; University of British Columbia's Adele Diamond; Silvia A. Bunge, Elliot Turiel, and Matthew P. Walker of University of California, Berkeley; Greg J. Duncan and Richard J. Haier, University of California, Irvine; Abigail A. Baird, Adriana Galvan, Michael Prelip, and Gary Orfield at the University of California, Los Angeles; University of California, Santa Barbara's Bella M. DePaulo; Claire Hughes, University of Cambridge; Susan Goldin-Meadow, University of Chicago; Antonius H. N. Cillessen, University of Connecticut; David F. Lohman and Larissa K. Samuelson at the University of Iowa; University of Kansas' Patricia H. Hawley and Dale Walker; Frederick W. Danner of the University of Kentucky; Roch.e.l.le S. Newman and Nan Bernstein Ratner at the University of Maryland; Linda R. Tropp, University of Ma.s.sachusetts, Amherst; Ronald D. Chervin, Jennifer Crocker, Denise Kennedy, and Louise M. O'Brien of the University of Michigan; Kyla L. Wahlstrom at University of Minnesota; Alan L. Sillars, University of Montana; E. Mark c.u.mmings at the University of Notre Dame; April Harris-Britt and Jane D. Brown of the University of North Carolina at Chapel Hill; David F. Dinges of University of Pennsylvania; University of Pittsburgh's Ronald E. Dahl; Judith G. Smetana, University of Rochester; at the University of Texas, Austin, Rebecca S. Bigler, Elizabeth A. Vandewater, and Mark Warr; Joseph P. Allen at the University of Virginia; Steven Strand, University of Warwick; Andrew N. Meltzoff at the University of Washington; C. Robert Cloninger of Washington University in St. Louis; and Peter Salovey of Yale University.

We'd also like to express our appreciation to: Deborah Linchesky at the American Academy of Pediatrics; Stephen C. Farrell of Choate-Rosemary Hall; Brian O'Reilly of the College Board; Donald A. Rock at Educational Testing Service; Anna Hogrebe at Elsevier B.V.; Lawrence G. Weiss of Harcourt Weiss / Pearson; Lauri Kirsch of Hillsborough County Public Schools; Lisa Smith and Stacy Oryshchyn of Jefferson County Public School District, Denver, Colorado; Gigi Ryner and Jackie Gleason of Stony Creek Preschool in Littleton, Colorado; Minnesota Regional Sleep Disorders Center's Mark W. Mahowald; Thomas D. Snyder, National Center for Education Statistics; Jay N. Giedd and Marc Bornstein at the National Inst.i.tutes of Health; Lisa Sorich Blackwell, New Visions for Public Schools; Richard L. Atkinson, Obetech LLC; Sally Millaway and Kathleen Thomsen of Neptune, New Jersey schools; Erin Ax at Effective Educational Practices; Judy Erickson, Sage Publications; the entire staff of the Society for Research in Child Development; Jessica Jensen and Debbie Burke of Van Arsdale Elementary School, Arvada, Colorado; and Bethany H. Carland of Wiley-Blackwell. Additionally, thanks to Joan Lawton, the staff and members of the Magic Castle in Hollywood, California, and Rose M. Kreider at the United States Census Bureau.

NOTES.

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