单选题 What new research reveals about the adolescent brain—from why kids bully to how the teen years shape the rest of your life. They say you never escape high school. And for better or worse, science is lending some credibility to that old saw. Thanks to sophisticated imaging technology and a raft of longitudinal studies, we're learning that the teen years are a period of crucial brain development subject to a host of environmental and genetic factors. This emerging research sheds light not only on why teenagers act the way they do, but how the experiences of adolescence—from rejection to binge drinking—can affect who we become as adults, how we handle stress, and the way we bond with others.
One of the most important discoveries in this area of study, says Dr. Frances Jensen, a neuroscientist at Harvard, is that our brains are not finished maturing by adolescence, as was previously thought. Adolescent brains "are only about 80 percent of the way to maturity," she said at the annual meeting of the Society for Neuroscience in November. It takes until the mid-20s, and possibly later, for a brain to become fully developed.
An excess of gray matter (the stuff that does the processing) at the beginning of adolescence makes us particularly brilliant at learning—the reason we're so good at picking up new languages starting in early childhood—but also particularly sensitive to the influences of our environment, both emotional and physical. Our brains, processing centers haven't been fully linked yet, particularly the parts responsible for helping to check our impulses and considering the long-term repercussions of our actions. "It's like a brain that's all revved up not knowing where it needs to go," says Jensen.
It's partially because of this developmental timeline that a teen can be so quick to conjure a stinging remark, or a biting insult, and so uninhibited in firing it off at the nearest unfortunate target—a former friend, perhaps, or a bewildered parent. The impulse to hurl an insult is there, just as it may be for an adult in a stressful situation, but the brain regions that an adult might rely on to stop himself from saying something cruel just haven't caught up.
In a paper published last year in the Journal of the American Academy of Child & Adolescent Psychiatry, Dr. Jay Giedd, a scientist at the Child Psychiatry Branch of the National Institutes of Mental Health, wrote that, according to brain scans conducted over several years, gray-matter volume peaks around or just before the beginning of puberty, and then continuously declines. In contrast, white matter (the stuff that helps connect areas of the brain) increases right up to, and beyond, the end of puberty.
These adolescent brain developments don't happen to all parts of the brain at the same time. "The order in which this maturation of connection goes, is from the back of the brain to the front of the brain," says Jensen.
And one of the last parts to mature is the frontal lobe, a large area responsible for modulating reward, planning, impulsiveness, attention, acceptable social behavior, and other roles that are known as executive functions. It's thanks in part to the frontal lobe that we are able to schedule our time with any sort of efficiency, plan in advance to arrange for a designated driver on a night out (or stop drinking before one is over the legal limit), and restrain ourselves from getting into fights any time we get involved in an argument. Unfortunately, it's just these sorts of behaviors that teenage brains are not fully endowed to deal with—and the consequences are potentially fatal when it comes to high-risk behavior like drinking and driving.
This blast of teen-brain change is compounded by profound social and psychological shifts. Of particular importance is that adolescence is the time when we develop stronger social connections with our peers, and more independence from our parents.
"Before the transition to adolescence, kids interact with one another, and the kinds of friendships that they have, are substantially different," explains Dr. Mitch Prinstein, professor and director of clinical psychology, at the University of North Carolina, Chapel Hill. "After adolescence they can really confide in friends, they turn to them as first sources of social support. Kids tell us all the time they are more likely to tell their friends about things going on in their lives, and stressors, than any adult. "
This cuts both ways. Healthy relationships have a positive effect on how an adolescent navigates through a tumultuous period of life. But at the same time, this reliance on friends makes young people susceptible to the influence of peer pressure, even when it is indirect.

单选题 One of the most important discoveries in the adolescent brain is that adolescent brains ______.
A. have become fully developed
B. are mainly affected by environmental and genetic factors
C. are particularly sensitive to activities such as drinking
D. remain immature

单选题 Teenagers are likely to ______.
A. hurt the people closest to them
B. be indifferent to their environment
C. have bewildered parents
D. try to stop themselves from saying something cruel

单选题 Which of the following statements is correct?
A. At the beginning of adolescence, our brains' processing centers have been fully linked.
B. White matter volume peak just before the beginning of puberty.
C. All parts of the adolescent brain do not develop at the same time.
D. The maturation of connection goes from the front of the brain to the back of the brain.

单选题 With the maturity of the frontal lobe, teenagers ______.
A. can deal with high-risk behavior like drinking and driving
B. will avoid arguing
C. never get into fights
D. schedule their time efficiently

单选题 The author's attitude towards kids' reliance on their friends is ______.
A. positive B. objective C. subjective D. skeptical