“Emphasizing effort gives a child a variable that they can control,” she explains. “They come to see themselves as in control of their success. Emphasizing natural intelligence takes it out of the child’s control, and it provides no good recipe for responding to a failure.” In follow-up interviews,Dweck discovered that those who think that innate intelligence is the key to success begin to discount the importance of effort.

“The key is intermittent reinforcement,” says Cloninger. The brain has to learn that frustrating spells can be worked through. “A person who grows up getting too frequent rewards will not have persistence, because they’ll quit when the rewards disappear.”

The effect was indeed measurable—and sizeable. The performance gap caused by an hour’s difference in sleep was bigger than the gap between a normal fourth-grader and a normal sixth-grader. Which is another way of saying that a slightly-sleepy sixth-grader will perform in class like a mere fourth-grader. “A loss of one hour of sleep is equivalent to [the loss of] two years of cognitive maturation and development,” Sadeh explained.

A few scientists theorize that sleep problems during formative years can cause permanent changes in a child’s brain structure—damage that one can’t sleep off like a hangover. It’s even possible that many of the hallmark characteristics of being a tweener and teen—moodiness, depression, and even binge eating—are actually just symptoms of chronic sleep deprivation.

Every hour of weekend shift costs a child seven points on the test. Dr. Paul Suratt at the University of Virginia studied the impact of sleep problems on vocabulary test scores taken by elementary school students. He also found a seven-point reduction in scores. Seven points, Suratt notes, is significant: “Sleep disorders can impair children’s IQ as much as lead exposure.”

Teens who received A’s averaged about fifteen more minutes sleep than the B students, who in turn averaged fifteen more minutes than the C’s, and so on. Wahlstrom’s data was an almost perfect replication of results from an earlier study of over 3,000 Rhode Island high schoolers by Brown’s Carskadon.

Talwar has run hundreds of people through this test, and on the whole, their results are no better than chance. People simply cannot tell when kids are lying.

What really works is to tell the child, “I will not be upset with you if you peeked, and if you tell the truth, I will be really happy.” This is an offer of both immunity and a clear route back to good standing. Talwar explained this latest finding: “Young kids are lying to make you happy—trying to please you.” So telling kids that the truth will make a parent happy challenges the kid’s original thought that hearing good news—not the truth—is what will please the parent.

In Talwar’s peeking game, sometimes the researcher pauses the game with, “I’m about to ask you a question. But before I do that, will you promise to tell the truth?” (Yes, the child answers.) “Okay, did you peek at the toy when I was out of the room?” This promise cuts down lying by 25%.

Pushing a teen into rebellion by having too many rules was a sort of statistical myth. “That actually doesn’t happen,” remarked Darling… “Kids who go wild and get in trouble mostly have parents who don’t set rules or standards. Their parents are loving and accepting no matter what the kids do. But the kids take the lack of rules as a sign their parents don’t actually care—that their parent doesn’t really want this job of being the parent.”

“Ironically, the type of parents who are actually most consistent in enforcing rules are the same parents who are most warm and have the most conversations with their kids,” Darling observed. They’ve set a few rules over certain key spheres of influence, and they’ve explained why the rules are there. They expect the child to obey them. Over life’s other spheres, they supported the child’s autonomy, allowing her freedom to make her own decisions. The kids of these parents lied the least. Rather than hiding twelve areas from their parents, they might be hiding as few as five.

Even the really busy kids could be bored, for two reasons. First, they were doing a lot of activities only because their parent signed them up—there was no intrinsic motivation. Second, they were so accustomed to their parents filling their free time that they didn’t know how to fill it on their own. “The more controlling the parent,” Caldwell explained, “the more likely a child is to experience boredom.” …The Mod Squad study did confirm Linda Caldwell’s hypothesis that teens turn to drinking and drugs because they’re bored in their free time.

University of Rochester’s Dr. Judith Smetana, a leader in the study of teen disclosure, confirms that, over the long term, “moderate conflict with parents [during adolescence] is associated with better adjustment than either no-conflict or frequent conflict.”

But only 23% of the daughters felt that their arguments were destructive. Far more believed that fighting strengthened their relationship with their mother. “Their perception of the fighting was really sophisticated, far more than we anticipated for teenagers,” noted Holmes. “They saw fighting as a way to see their parents in a new way, as a result of hearing their mother’s point of view be articulated.”

In one study, a third of the children reacted aggressively after witnessing the staged conflict—they shouted, got angry, or punched a pillow. But in that same study, something else happened, which eliminated the aggressive reaction in all but 4% of the children. What was this magical thing? Letting the child witness not just the argument, but the resolution of the argument. When the videotape was stopped mid-argument, it had a very negative effect. But if the child was allowed to see the contention get worked out, it calmed him. “We varied the intensity of the arguments, and that didn’t matter,” recalled Cummings. “The arguments can become pretty intense, and yet if it’s resolved, kids are okay with it.” Most kids were just as happy at the conclusion of the session as they were when witnessing a friendly interaction between parents…

…being exposed to constructive marital conflict can actually be good for children—if it doesn’t escalate, insults are avoided, and the dispute is resolved with affection. This improves their sense of security, over time, and increases their prosocial behavior at school as rated by teachers. Cummings noted, “Resolution has to be sincere, not manipulated for their benefit—or they’ll see through it.” Kids learn a lesson in conflict resolution: the argument gives them an example of how to compromise and reconcile—a lesson lost for the child spared witnessing an argument.

In one celebrated example, Dr. Robert Emmons, of the University of California at Davis, asked college students to keep a gratitude 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 gratitude journal were 25% happier, were more optimistic about the future, and got sick less often during the controlled trial. They even got more exercise.