Welcome to Your Child's Brain: How the Mind Grows From Conception to College (35 page)

As we noted in that chapter, the effect of genes appears far weaker under conditions of deprivation. If the environment is sufficiently impoverished, there is little or no correlation between genetic inheritance and intelligence. This probably happens because such environments offer children few opportunities to develop their genetic potential. Thus improving the environment may paradoxically increase the apparent contribution of genetic factors to individual differences. Similarly, a meta-analysis shows that adopted children have higher IQs, on average, than their siblings who remained in the birth family, presumably because adoptive families with higher socioeconomic status provide an environment better suited to cognitive development (see
chapter 30
).

Curiously, although researchers have identified about three hundred genes associated with mental retardation, it has proven difficult to link particular genes to normal variations in intelligence. One reason, of course, is that intelligence is influenced by many genes—which makes isolating them that much harder.
For comparison, forty genes are known so far that contribute to height, but they explain a total of only 5 percent of variation among individuals; more than likely, many more height genes remain to be identified. The genetics of intelligence seems likely to be even more complicated.

Parents can encourage their children to handle failure constructively by praising them for what they do rather than for what they are.

Brain structure itself is heritable and is correlated with intelligence. This correlation becomes stronger with age, and both measures are influenced by similar genes. Overall brain size moderately predicts intelligence (though there are exceptions, most notably that men have larger brains than women but equal intelligence), as do the volumes and cortical thickness of various brain regions. In a longitudinal study of children, the pattern of developmental changes in cortical thickness predicted intelligence more strongly than did the adult configuration at age twenty (see
chapter 9
). Dendritic branching in neurons was also correlated with intelligence in a few studies.

As you might imagine, intelligence is not located in a single brain region. Reasoning requires the transfer of information between brain regions, so brain connectivity is important. Among the major bottlenecks are certain long-distance connections within the brain; intelligence is correlated with making these connections easily and effectively. One study found that links from a region of the prefrontal cortex to the anterior cingulate and parietal cortex were stronger in more intelligent children and adolescents.

In adulthood, a network of frontal and parietal cortex regions seems to be most important for intelligence. In patients with brain damage, lesions in the left frontal and parietal cortex impair working memory, a key component of intelligence. Damage to the left inferior frontal cortex impairs verbal comprehension, and right parietal damage impairs perceptual organization. An area called the
rostrolateral prefrontal cortex
seems to be activated specifically during tasks that require you to integrate multiple mental representations, as when plotting your next move in a game of chess.

A handful of imaging studies suggest that children may use their brains differently from adults during abstract reasoning. Compared to adults, children ages six to thirteen recruit the rostrolateral prefrontal cortex for easier tasks. Children use this brain area to answer single-relationship questions like “What is the best match to a fish? (a) field, (b) water, (c) tree, (d) oatmeal,” while adults activate it only for two-relationship questions, such as verbal analogies (“Leaf is to tree as petal is to what?”).

The role of the environment in the development of intelligence is also substantial, but it has proven more difficult to define, in part because of the gene-environment interaction discussed earlier in this chapter. James Flynn—a moral philosopher who turned to social science and statistical analysis to explore his ideas—was the first to note one strong environmental effect on intelligence. Average IQ scores have risen recently by three points per decade in many countries, and even faster in some countries, such as the Netherlands and Israel. For instance, in verbal and performance IQ, an average Dutch eighteen-year-old in 1982 scored twenty points higher than the average person of the same age in his parents’ generation in 1952. The same improvement was seen when these eighteen-year-olds were compared with their own fathers at a similar age. By now the existence of the
Flynn effect
has been established beyond any reasonable doubt.

It might be tempting to say that this younger generation had evolved to be more intelligent than their parents, but evolution takes much longer than a few decades. Flynn points out that modern times have increasingly rewarded complex and abstract reasoning, and that this has been happening for over a century. This environmental change may be responsible for increasing IQ over time, both directly (by increasing your child’s reasoning ability) and indirectly (by increasing the reasoning ability of others in your child’s social group and thus making the social environment more complex). The change appears to be restricted to fluid intelligence, since capacities requiring less of it, such as vocabulary or arithmetic, have not shown comparable increases.

So if changes to the world can make your kids more intelligent, shouldn’t we be able to control that as parents? Well, yes and no. Some experimental interventions can increase intelligence—in children and even in adults. But there’s a catch: the successful approaches all require a lot of hard work in exchange for a small increase in reasoning ability. There are good reasons for your child to devote months to learning to play a musical instrument, but a gain of three IQ points
isn’t the first among them (see
Practical tip: The benefits of music and drama
). Similarly, in adults, extensive practice on a difficult working memory task leads to a four-point IQ gain. Researchers do not yet know whether such gains last after you stop training or whether they translate to improved professional or academic performance—or any other desirable outcome. These studies are promising, but they are not yet ready for widespread application.

You have probably seen a variety of advertisements for products that claim to increase your child’s brainpower, but we are skeptical of their value. The marketing departments have gotten far ahead of the data in claiming gains in brain function from programs that have not been tested adequately—or in most cases, at all. Some of these programs are actively detrimental to children’s development (see
Practical tip: Baby videos do more harm than good
). Even those that do no damage directly are displacing other activities that may benefit children more, such as free play (see
Practical tip: Imaginary friends, real skills
) or time spent outdoors (see
Practical tip: Outdoor play improves vision
).

In all, we suspect that unless your children enjoy such activities for other reasons, their time may be best spent discovering the pursuits that motivate them to achieve excellence for their own satisfaction. Childhood offers the chance to develop a variety of abilities that are important to a well-balanced life. Once your child has found an activity that matches his interests and abilities, you may find that effort and opportunity take care of themselves.

Chapter 23
TAKE IT FROM THE TOP: MUSIC

AGES: BIRTH TO NINE YEARS

Significant parts of this book were written to the soaring accompaniment of Sam’s three-year-old daughter belting out the songs of the ABBA musical
Mamma Mia
, over and over. When your child makes music, you’ve probably noticed that he seems able to stay focused for a long time—and that he finds it great fun. Whether it’s singing a favorite tune or banging away on an instrument, there’s something about music that can keep his attention for as long as half an hour, an eternity for a small child (and perhaps those listening to him).

Parents often try to deepen this relationship through lessons. The goals are not just aesthetic but practical: in coaxing their children to become more involved with music, many parents hope to improve their children’s minds. For this reason, when Sam was a child, his parents attempted to introduce him to the accordion, which thankfully did not stick, then to the violin, and finally to the piano, which did. Products like Brainy Baby purport to make infants smarter simply by exposing them to music at an early age.

Do these interventions do any real good? Based on research, the answer is mixed. Listening to music does not make children any smarter, but it does improve their moods, which leads to some secondary benefits. In contrast, there is some evidence for direct cognitive benefits from learning to play an instrument. In both cases, though, the research literature has to be taken with a grain of salt (see
Practical tip: The benefits of music and drama
).

The brain responds to music starting early in life, and musical aptitude continues to develop through age nine. As we discussed in
chapter 2
, the brain
develops from back to front, with the brainstem maturing first, followed by midbrain structures, and finally the neocortex. This general sequence is reflected in the order of development of a child’s capacities for recognizing music.

Music perception emerges not long after birth and becomes apparent during the first year of life. From the start, infants prefer higher-pitched singing to lower-pitched singing, as well as a song that is specifically directed toward them or sung in a loving tone. Babies can also perceive complex sounds such as a piano note, which combines multiple frequencies.

Infants even have innate ideas about what notes go together. One example is
consonance
, which occurs when one note occurs at a frequency that is at a simple multiple of another (for example, frequency ratios of 2 to 1, a perfect octave; or 3 to 2, a major fifth). You’ll find consonance in most songs, including simple children’s songs like “Twinkle, Twinkle Little Star.”
Dissonance
is used for effect in music but also occurs in abundance when your child bangs a fist on the piano. Infants look longer toward the source of a note when it is followed by a consonant note than when it is followed by a dissonant note such as an augmented fourth (F-sharp compared with C, a ratio of 45 to 32)—blech! This preference is apparent as young as two months of age. Indeed, dissonance is such a turnoff that when it occurs at the beginning of the experiment, infants check out permanently and stop looking at the speakers.

MYTH: THE MOZART EFFECT

The belief that passive experience leads to brain improvements is widespread. One of the most persistent brain myths is that playing classical music to babies increases their intelligence. There’s no scientific evidence for this idea, but sellers of classical music for children encourage the belief every chance they get.

This myth began with a 1993 report in the scientific journal
Nature
that listening to a Mozart sonata immediately beforehand improved the performance of college students on a complex spatial reasoning task. The researchers summarized the effect as equivalent to an eight- to nine-point gain on the Stanford–Binet IQ scale. Journalists were not especially interested in this finding when it was first published.

The turning point in this idea’s popularity was the publication of
The Mozart Effect
by Don Campbell, an influential bestseller. A low point of the craze was reached when Georgia governor Zell Miller played Beethoven’s “Ode to Joy” to the legislature and successfully persuaded them to spend $105,000 to send classical music CDs to all parents of newborns in the state. Almost two decades later, the idea that classical music makes babies smarter has been repeated countless times in newspapers, magazines, and books. It is familiar to people in dozens of countries. In the retelling, stories about the Mozart effect have progressively replaced college students with children or babies. Some journalists assume that the work on college students applies to babies, but others are simply unaware of the original research.