Teenagers

A friend told me that her 18 year old son had a few friends round last Saturday night. As she was getting into the car on Sunday morning she looked up and saw a line of beer cans all along his bedroom window. She ran back into the house and called up to him to sort it out. He called back in the usual teenage grunting tones that he would.

She left the house again and looked up at the window only to see him pulling down the blind!

That's teenagers.

Mine informs me that the teachers locked the sixth year out of their common room yesterday because it was in such a mess. So the kids held a protest, which included taking off their prefect badges. My sympathy is with the teachers, I just throw clean bedding and clothes into my son's room, and periodically demand the return of teaspoons, cups and plates.

New studies suggest that teenagers can't help being a surly bunch. Here's the relevant extract:

Giedd and his colleagues found that in an area of the brain called the prefrontal cortex, the brain appeared to be growing again just before puberty. The prefrontal cortex sits just behind the forehead. It is particularly interesting to scientists because it acts as the CEO of the brain, controlling planning, working memory, organization, and modulating mood. As the prefrontal cortex matures, teenagers can reason better, develop more control over impulses and make judgments better. In fact, this part of the brain has been dubbed "the area of sober second thought."

The fact that this area was still growing surprised the scientists. Although they knew that the brain of a baby grew by over-producing synapses, or connections, they had not known that there was a second period of over-production. In a baby, the brain over-produces brain cells (neurons) and connections between brain cells (synapses) and then starts pruning them back around the age of three. The process is much like the pruning of a tree. By cutting back weak branches, others flourish. The second wave of synapse formation described by Giedd showed a spurt of growth in the frontal cortex just before puberty (age 11 in girls, 12 in boys) and then a pruning back in adolescence.

Even though it may seem that having a lot of synapses is a particularly good thing, the brain actually consolidates learning by pruning away synapses and wrapping white matter (myelin) around other connections to stabilize and strengthen them. The period of pruning, in which the brain actually loses gray matter, is as important for brain development as is the period of growth. For instance, even though the brain of a teenager between 13 and 18 is maturing, they are losing 1 percent of their gray matter every year.
Giedd hypothesizes that the growth in gray matter followed by the pruning of connections is a particularly important stage of brain development in which what teens do or do not do can affect them for the rest of their lives. He calls this the "use it or lose it principle," and tells FRONTLINE, "If a teen is doing music or sports or academics, those are the cells and connections that will be hardwired. If they're lying on the couch or playing video games or MTV, those are the cells and connections that are going to survive."