For many parents, their children's preteen years could be compared only to a roller coaster ride.
Tumultuous, erratic emotions and unpredictable behavior are just a part of adolescence, and many parents have learned to just strap on their seat belts and hold on tight.
But why are some adolescents more emotional and susceptible to risky behaviors, while others remain steadfast in the face of peer pressure?
Dr. Marco Iacoboni, a professor of psychiatry and biobehavioral sciences at UCLA medical school, raised just that question about his 14-year-old daughter. So Iacoboni and a team of researchers sought to answer what might make adolescents give in to their friends and take more risks.
"When [adolescents are] among a group of people, they to tend to follow what others do, and being able to control their own emotions and actions can be very important," said Iacoboni, who is also the director of the transcranial magnetic stimulation lab at the Ahmanson-Lovelace Brain Mapping Center at UCLA.
Brain responses to emotional facial expressions would offer the first clue, he said.
Iacoboni and his colleagues took brain images of 38 adolescents over time as they were shown pictures of people expressing basic emotions, such as fear, happiness, sadness, anger, and neutrality. The researchers found that as the adolescents looked at faces expressing happiness or sadness, the area of the brain that expressed control over emotions showed increased activity.
The same group of adolescents reacted less emotionally to the other expressions, and the area of the brain associated with risk-taking and pleasure seeking lit up.
Previous research indicated that increased activity in the amygdala, an area deep in the brain, among preteens is associated with a higher likelihood of engaging in risky behavior, such as experimenting with drugs or sex.
"The assumption was more activity in there meant it was bad for the kids," said Iacoboni. "But we found higher activities and desires in other areas of the brain made them less prone to follow other kids."
"We saw there's an inverse activity relationship between the amygdala and the ventral striatum," said Iacoboni. "The VS activity increased while the amygdala activity slightly decreased, so the VS regulates the amygdala."
But could a test like this predict whether a preteen is more likely to act out or succumb to peer pressure? Iacoboni said it's still too early to tell.
The study didn't control for other factors in the adolescents' lives, such as socioeconomic status, current behavior and life influences that could contribute to future behavior.
The adolescents were tested twice over two years, once at age 10 and again at age 13. The researchers plan to test the group once again when they're 16.
"The more we get these snapshots of how the brain changes over time, the more we'll be able to see how dynamic a young person's brain is," Iacoboni said. "With this information, we can potentially direct the brain in another course."
The research so far suggests that facial expressions and emotions directed at adolescents may influence their brain response and, potentially, how they act.
Perhaps parents who express -- or controll -- their emotions around their preteens could influence the way they express or hold back their emotions around others, Iacoboni said.
"Sometimes staying neutral or apathetic is not the best choice, but don't be over emotional," he said. "You want to show warmth, because it'll be good for their social competence in life."