Welcome to Your Child's Brain: How the Mind Grows From Conception to College (4 page)

Babies can distinguish cats from dogs—a feat that is extremely difficult to program into a computer.

The third talent: babies distinguish
objects
from
agents
and treat them very differently. Infants—like all other people—understand that objects are cohesive (all the parts of the object stick together), solid (something else can’t go through an object), and continuous (all the parts of an object are connected to other parts), and only move when something touches them. For many years, it was accepted that infants under eighteen months did not understand
object permanence
, the idea that objects continue to exist even when you can’t see them. This bit of popular wisdom, originally disseminated by the pioneering psychologist Jean Piaget, was recently challenged by researchers who found the right ways to test infants.

Well before their first birthday, infants look longer if an object fails to be cohesive, solid, continuous, or permanent. In one experiment, five-month-old babies saw a car roll down a track whose middle section was hidden behind a screen. When a boxlike obstruction was then placed on the track behind the screen, five-month-old babies appeared to expect it to stop the car. How do we know this? When researchers secretly removed the obstruction through a trapdoor, and the car continued to roll down the track successfully, the babies looked longer at the screen, suggesting that they were surprised that the box was not solid. When evaluated in this way, babies as young as three and a half months old show that they can think about objects that are out of view behind other objects.

MYTH: IF ANYTHING GOES WRONG, MOM IS TO BLAME

Sigmund Freud has a lot to answer for. His ideas were speculative and eventually discredited by further research, but they have left deep impressions on our culture. One of the most pervasive ideas is that a baby’s relationship with his or her mother serves as a model for all later relationships in life. This idea has led many people to conclude that a mother’s behavior has an incredibly strong influence on what kind of a person her child will later become. From this belief, a culture has arisen in which complete strangers feel a moral obligation to intervene if they see a pregnant woman having a sip of wine or a mother yelling at her young son. In the past, psychiatrists even blamed mothers for their children’s autism or schizophrenia—both developmental disorders that are largely due to genetic mutations.

It’s time to relax. Now that you know that children actively participate in their own development, it should be clear that parents do not need to be perfect. We don’t recommend yelling, but that’s mostly because it’s an ineffective way to modify your child’s behavior (see
chapter 29
), not because your occasional bad mood is likely to do any serious, lasting damage to his psyche. Anyway, as you’ll see in
chapter 17
, parenting style has much less influence on personality than most of us believe. We’d like to see parents enjoying their kids more, rather than worrying over every aspect of their growth. That approach would be just as effective in producing healthy adults—and much more fun for everyone.

Babies also recognize agents, beings that have intentions and goals and can move on their own. Hands, for instance, always belong to agents. If six-month-old babies see a hand reaching for one of two objects, they seem to understand that the person wants that particular object. When the location of the objects is then reversed, the babies look longer if the hand reaches for the same location (but a different object) on the second try. If instead a stick pokes the object, babies don’t act surprised when the stick fails to follow the object to a new location, because a stick is not expected to act like a conscious agent.

Like adults, babies are willing to attribute agency to things that are not really
alive. When watching a film of a circle that seems to be chasing another circle, one-year-old babies look longer if the first circle moves away from the second circle than they do if the first circle moves straight toward its presumed target.

The fourth talent: babies organize information into categories and people into groups.
When infants as young as three months see a series of male faces, they spend less time looking at each new face, presumably because they’re bored with looking at men. When a female face then appears, they look longer. This is true even if the hair is not visible, so the babies seem to be using facial features, not hairstyles, to distinguish men from women. These categories are relevant for babies’ everyday lives. Most babies prefer looking at female faces to looking at male faces—except when their primary caretaker is male, in which case they are able to muster a slight preference for men.

Some broad categories like
animals
and
furniture
can be found very early in life; others are learned later. The boundaries of many categories, from the sounds of language to face perception, are shaped by experience to match your child’s local environment. But no one ever has to teach babies that categorizing things is a good strategy; it’s built into their brains. This ability provides a primitive basis for adult categorization, which makes it possible to think sensibly about newly encountered objects and people. It is also the root of stereotyping and prejudice, as we will see in
chapter 20
.

The fifth talent: babies select relevant information for attention while discarding most of what goes on around them.
As you may have noticed, babies are much less selective than adults about what captures their attention, but they still have distinct, automatic biases. From an early age, babies focus a lot on human voices, faces, and moving things. Babies start showing this preference for faces at thirty minutes after birth, and for human voices two days later. After three months of age, they notice objects that look distinctly different from surrounding objects, such as a red circle in a field of black circles.

Very early on, caregivers begin to influence the direction of a baby’s attention. Babies start to follow an adult’s gaze as early as four months of age. By twelve months they can point and direct their attention where someone else is pointing. At all ages, paying attention greatly increases the brain’s ability to learn about specific things. In computer models of brain function, innate biases in what information is given priority can provide a powerful mechanism for directing the learning of particular tasks. Babies’ innate interest in voices, for example, helps
them to learn about language. All of these talents help babies’ brains develop like dandelions, requiring only everyday types of stimulation that adults give normally—and instinctively.

In adults, these five talents are fundamental to the way our brains work. Indeed, in most of us these talents are inclined to be hyperactive. When we find ourselves considering our computers or our cars as if they had their own intentions and goals (typically in opposition to whatever we’d like them to do), our tendency to perceive agents is getting out of hand. When a baseball pitcher wins three games while wearing a certain pair of socks, and then insists on wearing his lucky socks whenever he plays, he is drawing conclusions about cause and effect from events that probably occurred together by chance.

From an early age, babies focus a lot on human voices, faces, and moving things.

There’s a practical reason why many of our scientific examples come from three-month-olds: younger babies are harder to test. Based on the evidence we have, our own belief is that these capacities are present from birth, at least in some primitive form. In the end, though, we don’t think it matters very much whether babies are born with these abilities or learn them soon after birth. Either way, babies start relying on these tools in infancy and continue to use them throughout their lives. On the other hand, these cognitive capacities are just the beginning. All of them become significantly more elaborate as babies grow and mature.

This emerging picture leaves little room for the outdated idea that babies are born with the potential to develop in any direction. Instead, they all start with certain biases. The cognitive talents that babies have in early life are essential for the development of their brains. Computer scientists who construct simulations to model what the brain does also confirm that biases are necessary to make these programs act realistically, even though our biases may limit us in some ways. They have not been able to explain convincingly how an adult brain might develop from a learning machine that starts with no predispositions.

As a consequence of these core talents, children’s brains come ready to learn how to adapt themselves to the environment that they encounter during development. This ability allows children to grow almost anywhere. Our species
has survived under a wide range of conditions through its history, and we have evolved to learn about the properties of the environment that were directly relevant to our survival. For this purpose, targeted learning mechanisms are often better than general mechanisms. These predispositions prepare the infant brain to learn many things—but not just anything.

Chapter 2
IN THE BEGINNING: PRENATAL DEVELOPMENT

AGES: CONCEPTION TO BIRTH

When we watch a house being constructed, we always find it surprising how quickly the framing is done. From the outside, the house looks almost complete very soon after it’s begun, but finishing the interior details and the wiring takes much longer. Building a brain is similar: getting the signaling cells, called
neurons
, into their correct positions is the (relatively) easy part, and it’s done before your baby is born. In contrast, wiring up all the connections is so complicated that the job won’t be entirely finished until your child is in college.

A baby’s brain is different from a house in one amazing way: from fertilized egg to newborn, its construction is largely automatic. The processes that form the brain are driven by a resilient genetic program, allowing babies to grow in almost any environment. Its main requirement is a healthy mother. As it says on the packaging of some of our favorite appliances, no assembly required.

This chapter will lay out some of the most valuable advice we have about prenatal development, including warnings about some of its hazards. But before we get into the details of what we found in the scientific literature, we want to emphasize this point:
most pregnancies turn out fine.
Authors of many popular advice books (you know who you are) convey the message that women must avoid any risky behavior while pregnant, no matter how minor. While long lists of potential problems may frighten mothers-to-be and help to sell books, those lists can also lead to prenatal stress, which itself is bad for the baby’s development (see
Practical tip: Less stress, fewer problems
).

The effects of prenatal risks depend on their timing and seriousness. In most cases, when miscarriages or birth defects do occur, they are not caused by the pregnant woman’s actions. Throughout your life, it will be tempting to blame yourself for anything that happens to your baby or child, but keeping a clear perspective is essential.

Knowing a bit more can help you relax a little about the largely self-organizing process of prenatal brain development. At the same time, there are a few simple points to remember in which your involvement could make a difference. It is a technical subject, but bear with us; the basics are not as complicated as they might first sound.

The construction of the brain begins early in pregnancy. During the first month, chemical signals cause a group of cells in the developing embryo to start becoming the nervous system. Beginning three weeks after conception, the
neural plate
, a cell layer running along the length of the embryo, brings its edges together to form the
neural tube
, which will later become the brain and spinal cord.