An fMRI of the brain ... when choosing a course of action, teenagers hardly use the area of the brain involved in thinking about other people's emotions

Credit: Stanford University

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SYDNEY, 8 September 2006: New research shows what exasperated parents always suspected: that teenagers are thoughtless and selfish.

The study, presented by Neuroscientist, Sarah-Jayne Blakemore yesterday at the British Association for the Advancement of Science Festival in Norwich, England, showed that when choosing a course of action, teenagers hardly use the area of the brain involved in thinking about other people's thoughts. Furthermore they often fail even to think about their own.

Many areas of the brain are known to alter dramatically during adolescence. One area that continues to develop through the teenage years is the medial prefrontal cortex, a large region at the front of the brain associated with higher-level thinking, empathy, guilt and understanding other people's motivations.

Blakemore said she has found that the medial prefrontal cortex is under-used by teenagers when choosing a course of action. Instead, an area at the back of the brain involved in perceiving and imagining actions takes over.

"Thinking strategies change with age," said Blakemore, who is from University College London. "As you get older, you use more or less the same brain network to make decisions about your actions as you did when you were a teenager, but the crucial difference is that the distribution of that brain activity shifts from the back of the brain to the front."

In the study, teenagers and adults were asked questions about the actions they would take in a number of situations. For example, whether they would move to another seat if they had trouble seeing the screen at the cinema.

Although teenagers and adults chose similar responses, the medial pre-frontal cortex was significantly more active in adults than in teenagers. Teenagers, on the other hand, activated the posterior area of the brain known as the superior temporal sulcus – an area involved in predicting future actions based on past actions.

"The fact that teenagers use a different area of the brain than adults when considering what to do suggests they may think less about the impact of their actions on other people and how they are likely to make other people feel," said Blakemore.

While children start to think about other people's mental states at around age five, this new data shows that the neural basis of this ability continues to develop and mature well past early childhood.

In another study, participants aged eight to 36 years were asked how they would feel and how they would expect someone else to feel in a series of situations, for example, after an argument with their best friend. Adults were far quicker than teenagers at judging emotional reactions – both how they would feel and how a third party might feel.

"It seems that adults might be better at putting themselves in other people's mental shoes and thinking about the emotional impact of actions," said Blakemore. But she cautioned that more research is required to know for sure.

"The relative difficulty that teenagers have could be down to them using a different strategy when trying to understand someone else's perspective - perhaps because the relevant part of the brain is still developing," said Blakemore. "The other factor to consider is that adults have had much more social experience."

"Whatever the reasons, it is clear that teenagers are dealing with not only massive hormonal shifts, but also substantial neural changes," said Blakemore. "These changes do not happen gradually and steadily ... they come on in great spurts, and puberty is one of the most dramatic developmental stages."