Brain Rules for Baby (Updated and Expanded). John Medina

responses are complex enough that it takes time to properly tune every connection. That’s what the first year of life is for. If the infant is marinated in safety—an emotionally stable home—the system will cook up beautifully. If not, normal stress-coping processes fail. The child is transformed into a state of high alert or a state of complete collapse. If the baby regularly experiences an angry, emotionally violent social environment, his vulnerable little stress responders turn hyperreactive, a condition known as hypercortosolism. If the baby is exposed to severe neglect, like the Romanian orphans, the system becomes under-reactive, a condition known as hypocortisolism (hence, the blank stares). Life, to quote Bruce Springsteen, can seem like one long emergency.

      What happens when parents fight

      You don’t have to raise kids under death-camp conditions to see negative changes in baby brain development. All you need are parents who, on a regular basis, wake up wanting to throw emotional punches at each other. Marital conflict is fully capable of hurting a baby’s brain development. The effects begin early and, though there is some controversy about this, may echo clear into adulthood.

      Every parent knows children become stressed when their kids see them fighting. But the age at which they can react was completely unexpected by researchers. Infants younger than 6 months old can usually detect that something is wrong. They can experience physiological changes—such as increases in blood pressure, heart rate, and stress hormones—just like adults. Some researchers claim they can assess the amount of fighting in a marriage simply by taking a 24-hour urine sample of the baby. Babies and small children don’t always understand the content of a fight, but they are very aware that something is wrong.

      Difficulty regulating emotions and much more

      The stress shows up behaviorally, too. Babies in emotionally unstable homes are much less able to positively respond to new stimuli, calm themselves, and recover from stress—in short, regulate their own emotions. Even their little legs sometimes won’t develop properly, as stress hormones can interfere with bone mineralization. By the time these children are 4 years old, their stress hormone levels can be almost twice as high as children in emotionally stable homes.

      And that’s sad, because the effects are fully reversible. Even infants younger than 8 months who are taken from severely traumatized homes and placed in empathic, nurturing environments can show improvements in their stress-hormone regulation in as little as 10 weeks. All you have to do is put down the boxing gloves.

      If marital hostility continues, the children show all the unfortunate behavioral signs of long-term stress. They are at greater risk for anxiety disorders and depression. They catch colds more often, because stress cripples the immune system. They’re more antagonistic toward peers. They’re less able to focus attention or regulate their emotions. Such children have IQs almost 8 points lower than children being raised in stable homes. Predictably, they don’t complete high school as often as their peers and attain lower academic achievement when they do.

      If we take the end point of this instability—divorce is a convenient target—we observe that kids are still paying for it years later. Children from divorced households are 25 percent more likely to abuse drugs by the time they are 14. They are more likely to get pregnant out of wedlock. They are twice as likely to get divorced themselves. In school, they get worse grades than children in stable households. And they are much less likely to receive support for college. When marriages stay together, 88 percent of college-bound kids will receive consistent support for their college education. When marriages fall apart, that figure shrinks to 29 percent.

      So much for Harvard.

      Reconcile in front of your kids

      Even in an emotionally stable home, one without regular marital hostility, there will be fights. Fortunately, research shows that the amount of fighting couples do in front of their children is less damaging than the lack of reconciliation the kids observe. Many couples will fight in front of their children but reconcile in private. This skews a child’s perceptions, even at early ages, for the child always sees the wounding but never the bandaging. Parents who practice bandaging each other after a fight, deliberately and explicitly, allow their children to model both how to fight fair and how to make up.

      The four biggest reasons you’ll fight

      Why will you fight? I mentioned four consistent sources of marital conflict in the transition to parenthood. Left to their own devices, all can profoundly influence the course of your marriage, and that makes them capable of affecting your child’s developing brain. I’ll call them the Four Grapes of Wrath. They are:

       • sleep loss

       • social isolation

       • unequal workload

       • depression

      If you have a child, you are statistically likely to tramp on at least a few of these when your baby comes home. The battle begins in bed—and no, it’s not about sex.

      1. Sleep loss

      If you know new parents, ask them if this complaint from “Emily” sounds familiar:

       I am spiteful of my husband because he gets to sleep through the night. My daughter is 9 months old and still waking up 2–3 times per night. My husband sleeps right through, and then wakes up “so exhausted.” I have not had more than 5–6 hours of sleep per night in the last 10 months, have an annoying toddler and a baby to deal with all day, and HE’s tired???

      We’ll address the marital disparity in this behavioral snapshot, but first let’s examine how little sleep Emily is getting and what it is doing to her marriage.

      It is hard to overestimate the effect that sleep loss exerts over couples in the transition to parenthood. Most parents-to-be have a notion that something will change at night. Most don’t realize how big it is going to be. Write this across your heart: Babies have no sleep schedule when they are born. The fact that you do does not occur to them. Sleep and eating times have no fixed pattern in the newborn brain; the behaviors are randomly distributed throughout a 24-hour period. There’s that social contract again. They take. You give.

      This can persist for months. A predictable schedule may not make itself visible for half a year, maybe longer, though most babies show some kind of organizing pattern by 3 months old. Between 25 percent and 40 percent of infants experience sleep problems in that time frame, a statistic observable around the world. Babies eventually acquire a sleep schedule; we think it is actually burned into their DNA. But there are many frequent disturbances in the dry, uncomfortable post-uterine world—some internal, some external—capable of keeping infants up at night. It just takes a while for their inexperienced brains to adjust. Even after a year, 50 percent still require some form of nighttime parental intervention. Because most adults require about half an hour to fall back asleep after they attend to an awakened child, moms and dads may go for weeks on end with only half the hours of sleep per night they need. That’s not healthy for their bodies. Not for their marriages, either.

      Sleep-deprived people become irritable—far more irritable—than people who are not. Subjects saddled with sleep debt typically suffer a 91 percent loss in their ability to regulate strong emotions compared with controls. The decline in general cognitive skill is equally dramatic (which is why chronically drowsy people don’t perform as well at work, either). Problem-solving abilities typically plummet to 10 percent of their non-drowsy performances, and even motor skills become affected. You have to be moderately sleep deprived for only a week to start getting these numbers. Mood changes occur first; cognitive changes come next, followed by alterations in physical performance.

      If you don’t have a lot of energy, and you are called upon to give to your youngest several times a minute (preschoolers demand some form of attention 180 times per hour, behavioral psychologists say), you quickly exhaust your reservoir of good will toward your spouse. Sleep loss alone can predict most of the increases in hostile interactions between new parents.

      2. Social isolation

      This rarely happens in a visit to the pediatrician’s office, but it should. The good doctor would ask you about