By Elli Leadbeater
Now we know why the surly teenager storms off in a huff after being told to tidy their bedroom.
Teenagers' brains work in different ways to those of adults
Adolescents do not put the part of the brain that considers others' feelings to full use, scientists have found.
It seems our neural decision-making processes mature quite slowly, and researchers think this might help to explain typical teenage behaviour.
The adolescent brain undergoes massive changes and does not reach maturity until 20 or 30 years old.
Details of the study were reported here at the British Association's annual Science Festival.
"The brain is pre-programmed to undergo massive changes during adolescence," Sarah-Jayne Blakemore of University College London told the meeting.
Dr Blakemore and her team used a sophisticated fMRI scanner to measure the brain activity of teenagers between 11 and 17, and young adults between 21 and 37.
The fMRI technique measures blood flow in different brain areas, and can identify "hotspots" where a lot of activity is taking place.
The volunteers were asked to think about what they would do in certain situations that involved their own actions.
For example, the researchers might say: "You want to go to the cinema. Do you look at the newspaper?"
MRI scans can identify regions of high brain activity
When thinking about what they would do, both age groups used the same neural pathway; but different parts of the pathway were most active in the two groups.
Adults used a brain area towards the front of the pathway, called the medial prefrontal cortex, to come up with their answers. Adolescents showed more brain activity in the superior temporal sulcus - an area at the rear.
"The superior temporal sulcus is usually used in making simple actions, or watching other people make actions," said Dr Blakemore. "We think adolescents are performing this task by simply thinking about the action they're going to take.
"The part of the brain that the adults are using more is involved in much higher level thinking, such as thinking about the consequences of your actions in terms of other peoples' emotions and feelings."
As a control, the study subjects were asked questions that did not involve their own actions, such as, "It's been raining hard. Does the ground get warmer?"
These questions activated brain networks in a similar way in both groups.
The new research shows that hormones may not be fully to blame for typical teenage behaviour.
Teenage brains undergo large structural changes during adolescence, and do not reach full maturity until at least 20 or 30 years of age.
"If you're making decisions about how you treat teenagers, socially and legally, you need to take this new research into account," said Dr Blakemore.
"The brain of, for example, a typical 15-year-old boy is very much still developing; he's a very different person from himself at 25. His brain is very different."