An economist, a neuroscientist, and a nutritional biologist walk into a nursery. Each having claimed to have reviewed all the relevant peer-reviewed papers on early childhood, they have advice. Luckily, it’s not too contradictory.
Figure 1. We’re looking for childcare advice with the deep evidence-based logic of Mr. Spock, rather than the 20th century’s best-selling (often anecdotal) childcare advice of Dr. Spock, who devolved into a leftwing activist.
The neuroscientist, John Medina, reports in Brain Rules For Baby that at every lecture he gives, a father asks what he can do early to ensure his baby has the best shot at getting into Harvard. Medina’s answer? “Go home and love your wife!”
Figure 2. Of course if nature > nurture, by then it may be too late. In a previous era, the best advice might be to find the smartest partner possible. But now Harvard isn’t really a meritocracy so you’re just looking for an alum.
Medina reveals that “a baby’s brain intensely monitors the caregiving it receives. It is essentially asking such things as ‘Am I being touched? Am I being fed? Who is safe?’ If the baby’s requirements are being fulfilled, the brain develops one way; if not, genetic instructions trigger it to develop in another way.” Babies stress when parents fight and survival mode significantly inhibits development. Even in the best of marriages, there can be a basic problem: “Many couples will fight in front of their children but reconcile in private. This skews a child’s perceptions.”
A child’s arrival feels like you’ve just discovered the most important priority in the world - but if that’s really true, then the best thing you can do is invest in your marriage. Medina specifically recommends pursuing the Seven Principles for Making Marriage Work, a book we’ve discussed before that tries to get at the empirics of a good relationship (deeply knowing your spouse, cultivating gratitude, being available when the other is hurt, etc.) while avoiding threats (overbroad criticism, defensiveness, stonewalling, and contempt). Medina gives a taste of what happens when marriage fails: “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.”
Prioritizing your spouse may be harder than it sounds because, statistically, having children decreases marital satisfaction, with year one of being with an infant decreasing it the most. Medina attributes this to sleep loss, social isolation, unequal chore taking, and depression. The economist, Emily Oster, adds in Cribsheet another related factor: less sex. Before you avoid having kids altogether, recall the economist Bryan Caplan’s Selfish Reasons to Have More Children: “If you’re married with children, you’re [18% more] likely to be happy than if you’re single and childless. Taken too literally, the statistics imply that married couples require over a dozen kids to feel worse than childless singles.”
Social isolation is real: “Outside of their spouses, typical new parents have less than 90 minutes per day of contact time with another adult. A whopping 34 percent spend their entire days in isolation.” For moms who stay at home, social isolation from adults can persist for a long time. Even for introverts, the quality of one’s relationships is one of the greatest predictors of life satisfaction. The solution is simple - make a point of regularly getting together with friends and family - but it can be easy to put off (children require a lot, scheduling is a hassle, childcare is hard to arrange, the house is too much of a mess to host, etc.) The very early days may overwhelm, but dad may soon want to arrange for mom to see folks at least twice a week.
Figure 3. Solitary confinement is literally the toughest punishment in American prisons. Imagine adding an infant.
Meanwhile, “Household duties increase three times as much for women as for men when baby comes home.” Mom needs help. Depending on your family situation, that might mean dad stepping up, mom staying home, older kids adding chores, outside help being enlisted, or some combination of them all.
As we’ve discussed before, sleep deprivation has really bad effects, and Medina highlights what makes it especially bad for marital bliss: “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.” It’s all too easy to wander into those earlier discussed threats to marriage like overbroad criticism and contempt. Oster echoes “Lack of parental sleep contributes to depression (in both parents) and correspondingly to less-happy marriages. You need sleep to function, and sleep deprivation affects your mood.”
Alas, for the first three months of a child’s life, you’ll get little relief. He needs to be attended to all hours of the night and you just need to be aware that you’ll suffer. If you can have the help of an in-law or night nurse, great -- but mom may still need to be woken again and again if you’re breastfeeding. And Alice Callahan, the nutritional biologist, reports in the Science of Mom that “Research has shown that when people get eight hours of sleep that’s fragmented by being awoken four times during the night, their cognition and mood are impaired just as much as if they’d only gotten four hours of sleep.” In our household, my wife Ashley slept in the nursery and I remained in our bedroom - and I tried to be very sensitive to the fact that I was the one getting a full night’s sleep. The best thing I can recommend is watching this hokey video - the Happiest Baby on the Block - about how to calm your baby down - it worked surprisingly well in our case.
Figure 4. Initially our son slept in a Moses basket, which is really convenient because if your child cries too much, you just float him down the river.
When your child is three months old, you can now experience one of the most contentious debates in modern parenting: whether to rush to your child upon any whimper to try to soothe and establish trustworthy attachment to mom and dad… or whether to let your child cry it out without immediate relief. All three books agree. Medina the neuroscientist: “Overwhelmingly, the evidence shows that [the cry it out method] works—if you define ‘works’ as getting the child to quit crying during the night so that everyone can sleep through the night. And it works surprisingly quickly, typically within a week.” The economist Oster: “Sleep-training methods consistently improve parental mental health; this includes less depression, higher marital satisfaction, and lower parenting stress.” Remarkably, “One small (non-randomized) study reported that 70 percent of mothers fit the criteria for clinical depression at study enrollment, and only 10 percent after the [cry-it-out] intervention”. (Relatedly, Medina notes that “About half of all new mothers experience a transient postpartum sadness that vanishes within a few days.” But about 10-20% of women experience persistent depression. Depression of course can be related to everything else but if you’re doing your best at the rest - especially getting enough rest - clinical intervention may be necessary and has shown to be helpful.) For the nutritional biologist Callahan, the trick is that “Overwhelmingly, and across cultures, babies that self-soothe usually have one thing in common: they are put in their beds at night while they are awake… they manage the transition from wakefulness to sleep on their own at the beginning of the night, and having this skill, they’re able to do the same thing in the middle of the night as well.”
But the worry is that you are harming your kids - listening to cries and doing nothing is not pleasant! - maybe throwing them into that survival mode you want to avoid. Oster reports that one “study found that, in fact, infant security and attachment seemed to increase after the ‘cry it out’ intervention. It also found improvements in daytime behavior and eating as reported by the babies’ parents.” Oster continues: “A 2006 review of sleep-training studies, which included thirteen different interventions, noted the following: ‘Adverse secondary effects as the result of participating in behaviorally based sleep programs were not identified in any of the studies. On the contrary, infants who participated in sleep interventions were found to be more secure, predictable, less irritable, and to cry and fuss less following treatment.’” Callahan piles on: “A 2014 review summarized 12 trials of sleep training, including a total of 1,742 children aged birth to 5 years, and several more have been conducted since. Together, they find that sleep training leads to reduced bedtime struggles, fewer night wakings, longer sleep for both baby and parents, better maternal mental health, and even improved baby temperament and mood.”
All of which kind of makes intuitive sense: think of how bad you feel when you don’t get any sleep. Oster concludes: “There is no evidence of long- or short-term harm to infants; if anything, there may be some evidence of short-term benefits.” Callahan concludes:
“There is no evidence that sleep training will hurt your child. Those who think sleep training is harmful will cite scientific studies to back their assertions. But if you read those studies, you’ll find that they aren’t about sleep training; they’re about babies who were subjected to chronic neglect or abuse or were raised in orphanages, lacking strong attachment figures. Or they’re about nonhuman primates or rodents separated from their mothers for extended periods of time. These are examples of chronic, toxic stress.”
While early on, someone ought to be sleeping in the same room as your child as a defense against the rare but tragic threat of SIDS, after four months, kids who sleep alone sleep better and longer - and that advantage persists for years, such that at 2.5 years old, those who were sleeping alone early sleep for 45 extra minutes. Co-sleeping can be a deeply intimate time with your child and sometimes may be the only option to get an infant to stop crying and go to sleep - but, as a default, it means lower sleep quality for mom and baby. It’s also an unfortunate truth that the majority of SIDS deaths occur in co-sleeping situations. Callahan notes that “a baby whose parents have followed all the ‘rules’ (breastfeeding, room sharing but not bed sharing, no smoking or alcohol) has a one in 12,500 chance of dying of SIDS.” Alcohol is especially dangerous: “sleeping next to an adult who’s had more than two drinks increases the risk a full eighteenfold.”
Otherwise, the best sleep practices for baby are basically the same for yourself. You want a consistent, early bedtime that is accompanied by soothing rituals that may involve bath, reading, snuggling, prayer, dim lighting low on blue light, in colder than you think temperature: “Keep your baby warm using pajamas and a sleep sack rather than loose bedding. Don’t overbundle him; dress him just enough to stay warm. The head is an important area for heat dissipation, so avoid using a hat for sleep. Ideal room temperature is thought to be 61° to 68°F.”
Figure 5. Amazingly enough, neither water nor you freeze at 61 degrees.
The final subject we’ll address in this email is the importance of diet, which of course begins before your child is even born. Medina argues that the best thing you can do in the first half of your pregnancy is to leave your child alone. Well, maybe there’s one thing you can do: “Women who take folic acid around conception and during the first few weeks of pregnancy are 76 percent less likely to create a fetus with neural tube defects than those who don’t take the supplement. It is the first thing you can do to aid brain development.”
Notably, morning sickness is correlated both with a healthier kid - and a smarter one. “One study, yet to be replicated, looked at children whose mothers suffered from major nausea and vomiting during pregnancy. When the children reached school age, 21 percent scored 130 or more points on a standard IQ test, a level considered gifted. If their mothers had no morning sickness, only 7 percent of kids did that well.” It may encourage mom to eat a “bland, boring diet—if she eats much at all” and reduce physical activity. (Emily Oster complains at how annoyed she was during intense morning sickness that her husband was giddy.)
But around four months, mom should ideally pick things up - engaging in moderate aerobic exercise (fit women have easier labor, smarter babies) and eating daily fruits, vegetables, eggs, and, at reasonable frequency, salmon. Medina says “Mothers who ate more fish starting in the second trimester had smarter babies than those who didn’t. By smarter, I mean that the babies performed better on cognitive tests that measure memory, recognition, and attention at six months post-birth.” As for cravings, “Is there any evidence you should pay attention to these cravings? Is the baby telegraphing its nutritional needs? The answer is no.” Eating for two should mean extra motivation for eating healthier, not an excuse for eating a lot more.
Finally, you should, to the degree possible, avoid severe stress, especially feelings of helplessness, because it has bad effects. When you actually give birth, a conventional exit is better because of “bacterial baptism” - according to Callahan, “Epidemiological studies have consistently found that children born by cesarean have a greater incidence of obesity and chronic conditions such as asthma, food allergies, and inflammatory bowel disease.”
Once your child is actually born, the neuroscientist Medina insists that you should try to breastfeed for a year because “you’ll get a smarter baby, a healthier baby, a happier baby. Breast-feeding is one of the most practical, brain-boosting behaviors we know. The benefits are extremely well established.” Callanan remarkably reports: “Some research suggests that a sick baby can even send signals via its saliva into the mother’s breast, which in turn produces milk that’s enriched in immune factors to help the infant fight off illness.” Medina again: “Breast-fed babies in America score on average 8 points higher than formula-fed kids when given cognitive tests, an effect still observable nearly a decade after the breast-feeding has stopped. They get better grades, too, especially in reading and writing.” On the ever important topic of sleep, Callanan notes that “Breastfed babies also have the benefit of melatonin in nighttime breast milk, which drops to undetectable levels during the day.” And a potentially interesting corrective, Oster notes, is that colic is correlated with a bad diet of mom. Oster also reports that breastfeeding can reduce a woman’s risk of breast cancer by “20 to 30 percent.”
Which all sounds magical, but both Oster and Callanan are less certain than Medina because women who choose to breastfeed tend to be more educated and smarter. Callahan notes that a randomized control trial - the gold standard for studies - “would also be unethical, because decades of research indicate that breastfeeding confers a range of health benefits.” But she does cite a clever study that looking at siblings, some breastfed, some not, to suggest that the effect is small. So, yes, this may be a correlation rather than causation but, as I often observe, if given the ability, why not lean into the correlations?
Eventually, around 6 months, you’ll add solid foods and the data say expose to allergens early. Oster recommends “do veggies first so kids do not learn fruit tastes better.” The trick - and this comes up again and again in the literature - is to give your kids repeated exposure to lots of healthy foods but not to coerce them into eating anything in particular. Starting early, we all have a deep desire for autonomy and leaning into that choice seems to yield better results. Oster summarizes: “offer your very young child a wide variety of foods, and keep offering them even if the child rejects them at first. As they get a little older, do not freak out if they don’t eat as much as you expect, and keep offering them new and varied foods. If they won’t eat the new foods, don’t replace the foods with something else that they do like or will eat. And don’t use threats or rewards to coerce them to eat.”
Figure 6. Our little pumpkin, after being eaten by our child.
According to another neuroscientist, Lisa Mosconi, as with your own diet, you should be sensitive to food’s glycemic index - a measure of how quickly carbohydrate-containing foods raise blood sugar levels - so that kids can have sustained, consistent energy (rather than unmanageable juice spikes and crashes). But kids’ brain development requires more saturated fat than the typical adult’s - in other words, meat. Callahan laments that meat is missing early: “in the United States, while about three out of four babies aged 6 to 9 months old are eating grains, vegetables, and fruits on a daily basis, just 17 percent are eating meat.” She concludes: “In an ideal world, I think babies do best eating meat, eggs, whole milk dairy products, a variety of grains and legumes, and lots of different fruits and vegetables.”
Invest in your marriage. Sleep well. Eat well. Turns out that the best advice for living remains true once you have kids. But that’s not all. More in a future email.
Figure 7. Click on the title to acquire Brain Rules for Baby (8/10) by the neuroscientist John Medina. He says “To make it into this book, studies must first have been published in the refereed literature and then successfully replicated. Some results have been confirmed dozens of times. Where I make an exception for cutting-edge research, reliable but not yet fully vetted by the passage of time, I will note it.”
Figure 8. Click on the titles to acquire Cribsheet (7.5/10) and Expecting Better (7/10) by the economist Emily Oster. She promises “a data-driven guide to better, more relaxed parenting”:
This book is going to argue for a more structured approach to making this choice. First, you get the data. You really confront—in an open-minded way—the question of whether there are any risks, and what these risks are. Are there any benefits? What and how big are they? Sometimes there are benefits to a choice, but they are so vanishingly small that it may not make sense to think about them very much. Likewise, sometimes there are risks, but they are infinitesimal relative to the other risks you take every day. And then, second, you combine this evidence with your preferences.
Oster is often contrarian - during pregnancy, “I believe the evidence supports consumption of both alcohol and caffeine in moderation” - but her views are grounded in a deep review of the available studies. She was rather infamous during covid for questioning why schools were not back in person - but she also has occasional comments in her book like bashing the lack of social services. Regardless, there’s plenty of insightful data, like “in the winter, on average, your kid will have a cold 50 percent of the time.”
Figure 9. Click on the title to acquire the Science of Mom (7.5) by the nutritionist biologist Alice Callahan. Starts with some annoying and irrelevant throat-clearing:
“The COVID-19 pandemic has turned our lives upside down in a year also marked by tumultuous politics, a long-overdue reckoning with systemic racism, and terrifying wildfires, which enveloped my town in smoke last month as the forests we love burned.” And comments along those lines occasionally come up again, though sometimes with self-conflict, as she both recommends meat consumption but laments it on scale. But there’s plenty of serious work within and updating for second edition meant “sifting through the research published in the past six or seven years to ensure that the science in this book is up to date, and because science is always moving us forward, that meant reading hundreds more papers.” For better or worse, she also reports skepticism based on funding source, “When I pull up a scientific paper for the first time, one of the first things I check is the affiliation of the authors, to see if they are from an academic institution or employed by a corporation, such as in the pharmaceutical, baby food, or formula industries”