Many people used to attribute the difference between the way teens think and the way adults think to the hormonal changes that occur during adolescence, or to a teenager's basic psychological need to be independent. But when scientists began looking at brain function in adolescents, using magnetic resonance imaging (MRI), they found that teenage brains actually work differently from adult brains.

In a recent study, scientists compared the brains of 18 children between the ages of 10 and 18 to those of 16 adults, using functional magnetic resonance imaging (fMRI). Both groups were shown photographs of adult faces. Researchers traced the activity levels in different parts of the brain as subjects were asked to identify the emotions depicted in the photos.

The results surprised the researchers. The adults in the study correctly identified a frightened expression, for example, as fear. Yet the teens in the study often described the same expression using words like surprised or angry. What's more, the teens and adults used different parts of the brain to process their analysis of the expressions. The teens mostly used the amygdala, an almond-shaped region that guides instinctual, or gut, reactions, while the adults relied on the frontal cortex, which governs reason and planning. As the age of the teens increased, the center of brain activity for this exercise shifted more toward the frontal cortex and away from the cruder response of the amygdala.

The scientists who conducted the research believe their study may partially explain why the teenage years are so emotionally turbulent for so many kids. The teens in the study not only seemed to misread the expressions on the adult faces in the photographs, but they reacted strongly from an area deep inside the brain. While the frontal cortex helped the adults distinguish subtlety of expression, this area wasn't fully operating in the teenagers.