In teens, only the limbic system responded. That finding jibes with brain mapping studies at the National Institutes of Mental Health, which show a period of intense neuron growth and refinement in the prefrontal cortex of adolescents between the ages of 9 and 18. Researchers have likened this period to building the mental muscle necessary to learn to think like an adult. In parts of the brain, the nerve coating called myelin isn't completely laid down until the post-teen years. Myelin acts as a sort of nerve insulator, funneling electrical impulses and helping nerves function more efficiently.
Violence is on the rise everywhere, but particularly so among the young.
The number of murders committed by children 14 to 17 years old has risen 165 percent since 1985, according to data compiled by the American Association for the Advancement of Science. Historically, boys have tended to exhibit overt disruptive or violent behavior more often than girls. Among girls of the same age group, the percentage is just 1.6 percent. But the ratio narrows significantly among boys and girls ages 12 to 16, with 8.3 percent of boys behaving badly compared to 6.7 percent for girls. Not surprisingly, national data shows that older girls get into trouble much more frequently than younger girls.