Brain development: Raging hormones are often implicated in teenager conduct but new research suggests that changes in the brain may also be important in understanding annoying teen behaviour.
Dr Sarah-Jayne Blakemore, a cognitive neuroscientist from University College London, said yesterday that for teenagers, "brains are still a work in progress".
Until recently it was thought that the brain did not change after the age of five. However, recent studies have indicated that the brain undergoes a second wave of development during puberty, and is not fully developed until 20-30 years of age.
Although boys and girls experience the same pattern of brain development, boys lag behind girls by approximately two years.
Dr Blakemore's research is unique in demonstrating that these changes in brain structure are accompanied by changes in the parts of the brain used to perform certain tasks.
Her work focuses on the frontal areas of the brain, the areas which "make us human". Previous research has demonstrated that these regions are involved in understanding the thoughts and feelings of others and in decision-making.
She used functional magnetic resonance imaging (fMRI) to see which parts of the brain were activated when volunteers were thinking about intentions.
Nineteen adolescents aged 11-17 years and 11 adults aged 21-37 took part in the study.
While they were in the brain scanner they read questions about various activities, such as "if you wanted to see a film would you phone the cinema?"
When thinking about these questions adults activated an area of the brain called the medial prefrontal cortex, which is implicated in empathy. However, the adolescents activated a different area, the superior temporal sulcus, which is farther back in the brain and is involved in representing physical actions.
"The adolescents were using more basic neural strategies," Dr Blakemore said. The young people were simply thinking about the actions involved in phoning the cinema.
Adults, however, were thinking more about the consequences of that action and what they should do in relation to other people. For example, in planning a trip to the cinema, adults might need to consider who they will go with and what time they are able to go.
The findings suggest that if teenagers appear to be self-centred and acting irresponsibly they may not be doing so on purpose. It may be because they are relying on less efficient brain mechanisms to navigate the social world.
The pattern of brain activation suggests that teenagers may not automatically consider the consequences of their actions or how other people feel about their actions. As a result they may engage in risky behaviour.
Dr Blakemore stressed that educators and policy makers needed to take these findings into account.