Welcome to Your Child's Brain: How the Mind Grows From Conception to College (34 page)

For a long time,
infantile amnesia
—the near-absence of memories from before one’s third birthday—was interpreted to mean that infants only have a primitive capacity to form memories. But young children can recall things that happened earlier, suggesting that information is stored but gets lost on the way to adult life. One possibility is that the brain is incapable of transferring memories into long-term storage in the neocortex. Recent evidence suggests that an alternative cause is instability of the initial memory.

As we described in
chapter 1
, infants can learn to form associations, as evidenced by their ability to learn to kick when their foot is attached by a ribbon to a mobile. When they get older, they outgrow this game, so that researchers have to come up with something more complex, such as pressing a lever to cause a miniature train to go around a track.

However, associative learning does not last long in infancy. At two months of age, babies remember for only a day. By three months, the duration increases to a week. After that, remembering grows steadily, until at eighteen months, children can remember simple associations for three months. With time, babies also develop another form of memory, the ability to remember complex actions that they’ve observed and imitate them later. Six-month-olds can reproduce a facial or body movement after a day. At eighteen months, they can make a more complex movement, like dressing a teddy bear, after a delay of four weeks.

Infant remembrance can be boosted with timely reminders. A six-month-old baby’s performance on the miniature train task lasts only two weeks after a single day of training, but a single additional session with the train doubles the retention time. Four reminders spread over six months lead babies to remember the task for a full year. Reminders are effective even if the initial association appears to be forgotten. As memories fade, reminders that are similar but a little bit off can distort the original memory, as also happens in adulthood. These findings raise the interesting possibility that appropriate reminders of an event that happened in early infancy could enable recollection of the event much later—perhaps even as an adult.

Synapses are modified not only when we encounter new information but also later, as memories are reprocessed. Perhaps surprisingly, memories appear to be rewritten frequently. Unlike a computer’s memory, a biological memory is reinforced by recall. It is as if the ink on a printed page got darker when the page was read. This process is known as
reconsolidation
, in which a stable (consolidated) memory is restrengthened. Changes can even happen offline when we are not actively thinking about the information, as memories are also strengthened during sleep (see
chapter 7
).

These changes in synapses and neurons participate not only in the learning of facts in school but in all changes in the developing brain. As it matures, your child’s brain undergoes transitions that go well beyond what we think of as learning. Socialization, the development of motor skills, and long-term changes in behavior and attention all rely on the fact that the brain is plastic, as inborn developmental programs and experience work together to shape your child’s brain.

Chapter 22
LEARNING TO SOLVE PROBLEMS

AGES: TWO YEARS TO EIGHTEEN YEARS

If your child believes that intelligence is a fixed characteristic, that belief will make her act less smart. Children who think a test measures their innate competence do not try as hard or perform as well as those who think that effort is the major determinant of success or failure. Because children who believe intelligence can’t be improved tend to see failure as a sign of low ability, they are likely to give up in shame when faced with a challenging task. In contrast, children who believe that hard work can improve their cognitive abilities often welcome difficult tasks and bounce back from failure, feeling that they have learned from the experience. For this reason, emphasizing the importance of intelligence to children may paradoxically reduce their chances of success.

Accordingly, interventions to change students’ views of intelligence can improve academic performance. In one longitudinal study, math test scores were static over two years in students who entered seventh grade believing that intelligence is fixed, while scores improved over time in their peers who believed that intelligence is influenced by experience.

The researchers then went to a different school and offered seventh graders an eight-week class (half an hour per week) on brain function and study skills. One group’s lessons included the idea that intelligence can be modified through practice, which leads to the formation of new connections in the brain. The other group got a lesson on memory. Later, the first group scored significantly higher on math tests than the second group, though the two groups had performed similarly before starting the class.

Parents can encourage their children to handle failure constructively by praising them for what they do rather than for what they are. Though telling a child that he is smart or artistic or athletic may seem like a good way to make him feel good about himself (see
Myth: Praise builds self-esteem
), it also teaches him to view those characteristics as fixed traits. On the other hand, praising your child for effort or improvement, or for choosing a particular way to respond to a problem, communicates that his behavior and choices are what matter to you. Since he can control his behavior but not his traits, that message is more empowering. (It’s also great to communicate that you’re on his team no matter what, but there are better ways to do that, such as saying “I love you.”)

PRACTICAL TIP: SOCIAL REJECTION REDUCES IQ

Because intelligence is so closely connected to working memory, a lot of events that distract you can make you temporarily less smart. In particular, unpleasant or awkward interactions with other people can greatly influence performance on tests of cognitive function.

In one study, college students in a randomly selected group were told that a personality test showed they were likely to end life alone, while a second group was given bad news of a different kind: they were told that the test showed they were likely to have many accidents later in life. The first group performed much worse on an IQ test or the analytical section of the Graduate Record Exam (GRE) immediately after the prediction. They also had more trouble recalling information for a difficult reading comprehension task. The effects were large, corresponding to a twenty-five-point drop in IQ.

Social rejection did not affect performance on less-demanding tasks. The two groups showed no difference in their ability to memorize nonsense syllables or their ability to answer easy reading comprehension questions. Based on these results, the researchers suggested that the prediction of future social rejection impaired the ability to reason because it depleted participants’ capacity for self-control (see
chapter 13
), a finding that was later confirmed.

Parents concerned about academic achievement might do well to focus on building their children’s self-control ability and social skills (
chapter 20
). There is good evidence that these capabilities can be modified by experience, and they contribute not only to a happy and successful life but also to intellectual achievement.

The question of how much circumstances can modify people’s intelligence remains controversial even among academics. This argument is ongoing partly because the development of intelligence has political implications for disadvantaged groups and partly because the issue is genuinely complicated. You may find this chapter easier to follow if you first go back and read
chapter 4
and the box
in
chapter 10
(
Practical tip: Outdoor play improves vision
) to remind yourself of how a trait can be highly heritable and strongly affected by the environment at the same time.

Let’s start by defining what we mean by
intelligence
. Individual people’s performance on any cognitive test is moderately predictive of their performance on any other cognitive test. These broad correlations between different cognitive skills reflect the existence of a general reasoning ability, often called
g
, which is measured (though not perfectly) by IQ tests. Intelligence can be subdivided into knowledge (
crystallized intelligence
) and reasoning skills (
fluid intelligence
).

People with better fluid reasoning skills process information more efficiently, reacting more quickly to stimuli and requiring less brain activity to solve problems. Intelligence is closely related to working memory, the ability to hold information in your mind temporarily while you’re doing something with it. Working memory can be as simple as remembering how much salt a recipe requires while you reach into the cupboard, or it can be as complicated as keeping track of the steps in a multistage process while you’re also evaluating whether it’s working correctly. People with good fluid reasoning ability are resistant to distraction; they are less likely to lose their place when they return to a task after temporarily turning their attention to something else.

During development, fluid reasoning ability first emerges at age two or three. It grows quickly until middle childhood and then more slowly until it reaches a plateau in midadolescence. After that, it declines very slowly through adult life and then more quickly in old age. (In contrast, crystallized intelligence continues to increase through adulthood and remains stable in old age, except in cases of dementia.)

There are many uncertainties involved in measuring (or perhaps defining) intelligence early in life, before it has fully developed. One of the best early predictors of IQ is habituation in infancy, that is, how quickly a baby becomes bored with a new stimulus and looks away. This measure is not very reliable, as it predicts only 17 percent of the variability in later intelligence and often produces different results when researchers retest the same child over time. Cognitive testing in babies and young children can distinguish mental retardation from normal intelligence but cannot distinguish moderate differences in normal intelligence. The results of IQ tests get progressively more stable through childhood, becoming fairly reliable around age seven or eight, and settling around the future
adult score by age twelve. In other words, young children’s brains are not finished enough to allow parents or teachers to determine who will turn out to be merely bright and who will be truly gifted.

Intelligence is a strong predictor of later academic and professional achievement, social mobility, and even physical health. Still, parents (and teachers and everyone else) should keep in mind that intelligence accounts for a bit less than half of the variation among individuals on most cognitive tests. The remainder of the test variance is attributable to mood, motivation, specific cognitive strengths and weaknesses, and experience with the particular test and with testing in general. Self-control too is important for later achievement; as we pointed out in
chapter 13
, the marshmallow test at age four predicts later SAT scores twice as well as IQ. Finally, life success depends not only on ability but also on opportunity and effort.

Twin and adoption studies demonstrate conclusively that genes can strongly influence individual differences in intelligence. Among middle-class populations, the heritability of intelligence increases substantially with age, from 30 percent in early childhood to 70–80 percent in late adolescence and adulthood. This change occurs partly because as people grow older, they become more able to choose environments that suit their personal characteristics. In particular, intelligent children tend to place themselves in intellectually stimulating circumstances if they can, which improves their cognitive development. This gene-environment interaction increases the apparent strength of genetic influences (see
chapter 4
).