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.

Olfactory recognition may also be the first step toward human bonding and attachment. As we\'ve seen, newborns quickly learn and prefer the scent of their own mother or other caretaker. Nursing babies clearly have the richest olfactory experience, being bathed several times a day in the odors of their mother\'s milk and areolar secretions. Nonetheless, bottle-fed babies also can learn their parents\' scents rather rapidly, depending on the amount and closeness of their contact. After the breast, a caregiver\'s neck is probably the most potent source of olfactory input, since it is often uncovered and close to a baby\'s nose when he is being held upright.

Young children are also known to recognize and prefer the odors of their own siblings, based on some more T-shirt sniffing experiments. Children as young as three years of age can correctly identify the odor of their own sibling, which undoubtedly contributes to the development of this special bond.

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Like prenatal smell, a fetus\'s taste experience in the womb may bias his or her later behavior—in this case, influencing food preferences. This has been clearly demonstrated in animal studies. For instance, baby rabbits whose mothers were fed juniper berries during pregnancy clearly preferred foods containing the aromatic juniper flavor when tested at the age of weaning. In another report, adult rats that had been exposed to apple juice before birth by amniotic injection showed a greater preference for apple juice than rats exposed to control or saline injections. And more worrisomely, adult rats that were exposed to alcohol in utero showed considerably more preference for it than rats that had not been exposed to alcohol before birth. If the same kind of \"memory\" occurs among the children of alcoholic mothers, it may in part explain why alcoholism tends to mn in families.

The fact that babies begin to taste before birth thus has important developmental consequences. Not only does it affect the formation of taste pathways and preferences, it probably also acts, like smell, to help babies recognize and find comfort with their mothers after birth, since many of the same dietary flavors that make their way into a woman\'s amniotic fluid will also be present in her breast milk.

Smell allows an infant to label its world, identifying its mother, father, and siblings; while taste prepares it for the environment it will be born into and influence its preferences for foods within its culture.