The notion of prenatal influences may conjure up frivolous attempts to enrich the fetus, like playing Mozart through headphones placed on a pregnant belly. In reality, the nine-month-long process of shaping and molding that goes on in the womb is far more visceral and consequential than that. Much of what a pregnant woman encounters in her daily life—the air she breathes, the food and drink she consumes, the emotions she feels, the chemicals she’s exposed to—are shared in some fashion with her fetus. They make up a mix of influences as individual and idiosyncratic as the woman herself. The fetus incorporates these offerings into its own body, makes them part of its flesh and blood. And, often, it does something more: it treats these maternal contributions asinformation, as biological postcards from the world outside. What a fetus is absorbing in utero is not Mozart’s Magic Flute, but the answers to questions much more critical to its survival: Will it be born into a world of abundance, or scarcity? Will it be safe and protected, or will it face constant dangers and threats? Will it live a long, fruitful life, or a short, harried one? The pregnant woman’s diet and stress level, in particular, provide important clues to prevailing conditions, a finger lifted to the wind. The resulting tuning and tweaking of the fetus’s brain and other organs are part of what give humans their impressive flexibility, their ability to thrive in environments as varied as the snow-swept tundra, the golden-grassed savanna—and the limestone canyons of Manhattan’s Upper West Side.

Diet and other environmental factors are data for the fetus about the conditions of the world outside the womb and influence its development to be best adapted to that environment.

If survival is the brain’s most important priority, safety is the most important expression of that priority. This is the lesson Harlow’s iron maidens teach us. Babies are completely at the mercy of the people who brought them into the world. This understanding has a behavioral blast radius in infants that obscures every other behavioral priority they have.

How do babies handle these concerns? By attempting to establish a productive relationship with the local power structures—you, in other words—as soon as possible. We call this attachment. During the attachment process, 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. It may be a bit disconcerting to realize, but infants have their parents behaviors in their sights virtually from the moment they come into this world. It is in their evolutionary best interests to do so, of course, which is another way of saying that they can’t help it. Babies have nowhere else to turn.

There’s a window of several years during which babies strive to create these bonds and establish perceptions of safety. If it doesn’t happen, they can suffer long-term emotional damage. In extreme cases, they can be scarred for life.

We know this because of a powerful—and heartbreaking—story from Communist Romania, discovered circa 1990 by Western reporters. In 1966, in an effort to boost the country’s low birthrate, the dictator Nicolae Ceausescu banned both contraception and abortion and taxed those who were childless after age 25—whether married, single, or infertile. As the birthrate rose, so did poverty and homeless-ness. Children were often simply abandoned. Ceausescu’s response was to create a gulag of state orphanages, with children warehoused by the thousands.

The orphanages soon were stripped of resources as Ceausescu began exporting most of Romania’s food and industry to repay the country’s crippling national debt. The scenes in these orphanages were shocking. Babies were seldom held or given deliberate sensory stimulation. Many were found tied to their beds, left alone for hours or days, with bottles of gruel propped haphazardly into their mouths. Many infants stared blankly into space. Indeed, you could walk into some of these hundred-bed orphanages and not hear a sound. Blankets were covered in urine, feces, and lice. The childhood mortality rate in these institutions was sickening, termed by some Westerners “pediatric Auschwitz.”

Horrible as these conditions were, they created a real opportunity to investigate—and perhaps treat—large groups of severely traumatized children. One remarkable study involved Canadian families who adopted some of these infants and raised them back home. As the adopted children matured, researchers could easily divide them into two groups. One group seemed remarkably stable. Social behavior, stress responses, grades, medical issues—all were indistinguishable from healthy Canadian controls. The other group seemed just as remarkably troubled. They had more eating problems, got sick more often, and exhibited increasingly aggressive antisocial behaviors. The independent variable? The age of adoption.

If the children were adopted before the fourth month of life, they acted like every other happy kid you know. If they were adopted after the eighth month of life, they acted like gang members. The inability to find safety through bonding, by a specific age in infancy, clearly caused immense stress to their systems. And that stress affected these children’s behavior years later. They may have been removed from the orphanages long ago, but they were never really free.

Babies that have their needs met grow up to be regular children, babies that are neglected, even in just the first four months, grow up to be gang members.