Welcome to Your Child's Brain: How the Mind Grows From Conception to College (30 page)

This ability, called
theory of mind
, involves several components that appear in stages. As early as three months, infants divide the world into objects and agents (see
chapter 1
). Their ability to identify agents, which act with purpose and goals, provides a foundation for understanding other minds.

Theory of mind can be sorted into two categories, which rely on different but overlapping brain systems. Over the first two years of life, children become able to react to other people’s perceptions and desires. In the second phase, also lasting about two years, children gradually develop a system for thinking explicitly—and talking—about the beliefs of others. By around age four, children possess a full-blown theory of mind.

The understanding of feelings can occur at different levels. The brain has a system for rapid processing of emotional stimuli, which reacts in a contagious manner to the feelings of others. This process involves the sensory neocortex, the thalamus, and the amygdala. With enough time, such processing can also involve the neocortex, including temporal and frontal areas, in a cognitive form of empathy.

Contrary to the wisdom of some folk psychology, many animals have the contagious form of empathy. Rhesus monkeys will refrain from pulling a chain that delivers an electrical shock to another monkey, even if they know that pulling the chain will bring them a large food reward. Rats can help each other as well. When confronted with a squealing, wriggling rat suspended in a sling, another rat will press a lever repeatedly to bring the suspended rat to the floor, staying close to it the whole time. So as originally suggested by Charles Darwin, empathy in its most basic form, the desire to assist members of one’s own species, is widespread among mammals.

Apes, which have a larger neocortex than rats or monkeys, are capable of more cognitive acts of empathy. For example, chimpanzees will comfort sick and injured birds, gently straightening their wings to aid their attempts to fly. (Showing a lack of foresight, they sometimes then toss the birds from high places.) They are also reported to help unfamiliar people in distress.

As the neocortex develops, children make the transition from rat- and monkeylike empathy to apelike empathy. As many parents and caregivers know, the presence of one crying baby in a nursery often starts the others crying. As children grow older, empathetic responses become more complex. Children imitate the distress behaviors of other children, as if trying them on to see how they feel. They soon shift away from feeling personal distress and start showing helping behaviors. In the second year of life, toddlers comfort younger siblings in distress by patting, hugging, or kissing them. Similarly, they may bring a security blanket to an adult in pain.

How does the baby’s brain generate contagious empathy? Many scientists believe that recognizing emotions in others involves experiencing the emotion yourself. Indeed, scans of brain activity in adults show that the insula is activated when they experience feelings of disgust—and when they look at disgusted faces (see
Did you know? Imitation in the brain
). Similarly, the amygdala is activated when we look at frightened faces and also when we feel fear ourselves.

By internalizing the emotions of others, children develop a sense that others have desires. This appreciation is clearly visible at twelve months; if a baby sees someone look at an object with positive emotion, she expects him to reach for it—and looks for a longer time if he does not. (This measure of violated expectations, spontaneous looking when something unexpected happens, is one of the ways to measure infant abilities. For more on this topic, see
chapter 1
.) Between fourteen and eighteen months, babies acquire the capacity to understand that when a grown-up has indicated a preference for a food, the baby should give it to him—even if the baby doesn’t like that food himself. You can see this when your toddler hands you a piece of asparagus (assuming you like asparagus). Children also begin to have some sense of what others feel about them, as shown in the development of self-conscious emotions such as embarrassment during the second year (see
chapter 18
).

DID YOU KNOW? OLDER SIBLINGS SPEED A CHILD’S THEORY-OF-MIND DEVELOPMENT

The ability to reason about the beliefs of others depends on brain maturation, but it is also influenced by experience. The more often a parent talks to a child about motivations and mental states, the sooner the child begins to demonstrate an explicit ability to speak in terms of the beliefs of others. An even stronger influence is growing up with older siblings. Having an older (but not younger) sibling speeds the onset of theory-of-mind capacity in three- to five-year-old children. The size of the difference is equivalent to an average of four to six months of advance per older sibling, for up to three siblings. By age six, nearly all children have acquired the same level of understanding, but there may be lasting social advantages to developing this capability earlier (see
chapter 20
). So in the preschool years, living with older siblings can help a child’s mind mature faster.

In parallel with these social emotions, babies between the ages of thirteen and twenty-five months also begin to develop a framework for understanding the perceptions and desires of other people. In one study, babies of twenty-five months saw a bear puppet stowing a toy inside one of two boxes for an observer to retrieve. Then, after hiding the toy again, the bear switched the toys while the observer was looking the other way. When the observer turned back, the children looked at the original box, as if expecting the observer to look in the wrong location. In other tests, young children also looked longer when people acted as if they knew something that they were not supposed to know, such as the location of a tasty snack that had been covertly moved. Putting on pretend scenes like these can be amusing to you and your child—and educational for you.

This level of sophistication is unique to people, but chimpanzees come close. They understand the goals and intentions of others, for instance, reaching for food that another chimp cannot see instead of food that is visible to both. But
researchers have not yet found a way to get chimps to act on the wrong belief of another chimp or human.

Preschoolers have one more hurdle in their development of theory of mind: they have to learn to verbalize their awareness of another person’s false belief. This ability arises well after children begin to talk. In one classic test of theory of mind, a child is told a story of two girls named Sally and Anne. Sally has a basket with a lid, and Anne has a box. While they are together, Sally puts a marble in her basket. Sally leaves, and while she is away Anne moves the marble to the box. When Sally comes back, where will she look for her marble? Most preschoolers will indicate Anne’s box, where the marble really is. Only around the age of four will children start indicating the basket, where Sally is likely to wrongly
think
her marble still is.

Gaining the ability to lie convincingly is a notable step in mental development

The ability to think about the thoughts and beliefs of others probably grows from earlier, more basic capacities. Activity measurements from the brains of adults provide an indication of where those earlier capacities might be localized. Parts of the neocortex near the posterior superior temporal
sulcus
are activated when people detect an agent, and the temporal poles of the neocortex are active when social knowledge is generated. The inferior parietal lobule is activated by visual motion or the direction of another person’s gaze, which conveys information about that person’s intention.

A key component of theory of mind in the brain is the medial prefrontal cortex. This region is active when people are asked to distinguish someone’s mental representation from a real-world physical state. The medial prefrontal cortex is also activated during humor, embarrassment, and other moral emotions. This region develops relatively late, as does long-distance communication between frontal and temporal regions, perhaps accounting for why these capacities only come together starting around age four.

Around age two, children start to play simple pretend games. A year later, they show a more elaborate understanding, doing things like putting on a raincoat and boots in sunny weather, then pretending to splash in puddles. The developmental psychologist Alison Gopnik calls these
silly mental states
—a third state of mind, separate from knowledge of the world and absolute ignorance. Silliness is pretense chosen on purpose, just for fun. Your children exercise this sense when they watch a puppet show and shout at the hero or heroine to watch out, or when you pretend not to know something. The ability to reach this state—and perhaps see it in playmates—may be a stepping-stone to a full-blown theory of mind.

DID YOU KNOW? IMITATION IN THE BRAIN

Sam once stuck out his tongue, with the sides curled up, at his baby daughter, and she was able to mimic him perfectly on her first try. This was quite a surprise. Such a complex act of imitation meant that she was able to generate a strange new facial expression simply based on seeing the movement—a complex mapping of a visual stimulus to a coordinated set of corresponding tongue muscle movements. Of course, you might be less of a geek than Sam, and just like the sight of your baby sticking her tongue out.

How can this imitation happen? Across many brain regions, direct experience activates some of the same neurons as vicarious experience. In electrical recordings from the premotor cortex, a frontal brain region, there are neurons that are activated when a monkey makes a specific movement, such as grasping a piece of fruit to bring it to the mouth. Researchers found that particular neurons, which they called
mirror neurons
, fired both when the animal performed such a movement and when the animal saw the same movement performed by someone else. Mirror neurons for specific actions are also found in the brains of people undergoing exploratory neurosurgery.

Mirror neurons have received a fair bit of hype in the popular press as mystical causes of a variety of other capacities, such as empathetic abilities. Although much of this discussion is overblown, there is a more general principle regarding how other people’s emotions and actions are represented in many areas across the brain.

For example, emotion-related brain areas show mirrorlike properties. Both strong negative emotions and the sight of a face expressing the same emotion trigger activity in the insula, a cortical region that communicates with other emotion-processing regions such as the amygdala. The insula also receives information from the premotor cortex, suggesting that mirror neurons could convey the emotional content of body language. Information goes in both directions between these brain regions, so they could even teach one another about emotions and their physical expressions.