Welcome to Your Child's Brain: How the Mind Grows From Conception to College by Sam Wang, Sandra Aamodt Page A
Authors: Sam Wang, Sandra Aamodt
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nap. In one experiment, college students were required to focus on the center of a screen when the letter T or L flashed, followed after a brief pause by some diagonal bars shown elsewhere on the screen. Students tested early in the day identified both the letter and the orientation of the bars even if they were flashed in quick succession. Later in the day, they needed the letters to be spaced at longer intervals for successful identification. This slowing of perceptual capacities was prevented if the students were allowed to take a brief nap. Naps not only keep toddlers from getting cranky but may also help adults’ mental performance.
So when you watch your baby or child sleeping, be aware that her brain is far from idle. Her brain is fulfilling a well-choreographed process that is coming along nicely without any special effort by her or you. While the sugarplums in her head might not be dancing, bigger things are changing—including events that may restore and rewire the developing brain.
Chapter 8
IT’S A GIRL! GENDER DIFFERENCES
AGES: BIRTH TO EIGHTEEN YEARS
Three-year-olds take gender roles as seriously as drag queens do. One of our colleagues, who was dedicated to freeing her kids from traditional gender expectations, bought a doll for her son and trucks for her daughter. She gave up her quest after she found the boy using the doll to pound in a nail and the girl pretending that the trucks were talking to each other.
Many puzzled parents have wondered where this highly stereotyped behavior comes from, especially in households where Mom wouldn’t be caught dead in a pink frilly dress and Dad would rather cook dinner than watch sports. All over the world, a phase of intense adherence to a sex role seems to be important for the development of a solid gender identity. This stubbornness reminds us of the early stage of grammatical learning, another area where young kids apply newly learned rules more broadly than necessary (“That hurted my foots” instead of “That hurt my feet”).
In light of their behavioral differences, you’d probably imagine that the brains of little boys and girls are distinct in many important ways. Because of our society’s intense interest in sex differences, researchers have done many thousands of studies of this topic, and journalists have been eager to publicize them. This literature is vast and variable, so as we evaluated it, where possible we relied on meta-analysis (see glossary) to evaluate the findings. From careful review of such papers, a few important patterns emerge.
When we evaluate reports of sex differences, it’s important to pay attention to the size of the effects. Most gender differences are too small to matter inany practical way, and a minority of differences are important when comparing groups. But only a few tell us anything significant about individuals. For instance, girls—on average—are more likely to hear a relatively quiet sound. But it would be impossible to guess whether a particular child is male or female by knowing that child’s hearing ability, because all possible scores are found in both boys and girls. And what’s more, for nearly all sex differences, the differences among individual girls or among individual boys are much larger than the average differences between the sexes, with a few important exceptions.
What do we mean when we say that a gender difference is small or large? Let us be technical for a moment. Scientists often measure the size of a difference between two groups by calculating a statistic called d-prime (d' ) or effect size , defined as the difference between groups divided by the standard deviation, a measure of variability, of one or both groups. If there is no difference, the d' is zero. The d' gets bigger as the size of the difference in average scores between the groups increases, relative to the range of scores within each group.
This idea is easier to explain in pictures than in words. The figure below
So when you watch your baby or child sleeping, be aware that her brain is far from idle. Her brain is fulfilling a well-choreographed process that is coming along nicely without any special effort by her or you. While the sugarplums in her head might not be dancing, bigger things are changing—including events that may restore and rewire the developing brain.
Chapter 8
IT’S A GIRL! GENDER DIFFERENCES
AGES: BIRTH TO EIGHTEEN YEARS
Three-year-olds take gender roles as seriously as drag queens do. One of our colleagues, who was dedicated to freeing her kids from traditional gender expectations, bought a doll for her son and trucks for her daughter. She gave up her quest after she found the boy using the doll to pound in a nail and the girl pretending that the trucks were talking to each other.
Many puzzled parents have wondered where this highly stereotyped behavior comes from, especially in households where Mom wouldn’t be caught dead in a pink frilly dress and Dad would rather cook dinner than watch sports. All over the world, a phase of intense adherence to a sex role seems to be important for the development of a solid gender identity. This stubbornness reminds us of the early stage of grammatical learning, another area where young kids apply newly learned rules more broadly than necessary (“That hurted my foots” instead of “That hurt my feet”).
In light of their behavioral differences, you’d probably imagine that the brains of little boys and girls are distinct in many important ways. Because of our society’s intense interest in sex differences, researchers have done many thousands of studies of this topic, and journalists have been eager to publicize them. This literature is vast and variable, so as we evaluated it, where possible we relied on meta-analysis (see glossary) to evaluate the findings. From careful review of such papers, a few important patterns emerge.
When we evaluate reports of sex differences, it’s important to pay attention to the size of the effects. Most gender differences are too small to matter inany practical way, and a minority of differences are important when comparing groups. But only a few tell us anything significant about individuals. For instance, girls—on average—are more likely to hear a relatively quiet sound. But it would be impossible to guess whether a particular child is male or female by knowing that child’s hearing ability, because all possible scores are found in both boys and girls. And what’s more, for nearly all sex differences, the differences among individual girls or among individual boys are much larger than the average differences between the sexes, with a few important exceptions.
What do we mean when we say that a gender difference is small or large? Let us be technical for a moment. Scientists often measure the size of a difference between two groups by calculating a statistic called d-prime (d' ) or effect size , defined as the difference between groups divided by the standard deviation, a measure of variability, of one or both groups. If there is no difference, the d' is zero. The d' gets bigger as the size of the difference in average scores between the groups increases, relative to the range of scores within each group.
This idea is easier to explain in pictures than in words. The figure below
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