Adolescents really do suffer a brain dysfunction, for a while

Professor David Skuse, of the Institute of Child Health in London, told the British Association for the Advancement of Science that hormonal surges at puberty may cause a rewiring of the brain of adolescents which interferes with their ability to interact socially with their elders.

"There is a temporary deterioration in children's capacity accurately to interpret emotions from facial expressions around the time of puberty," he said. "This may go some way to explaining the 'Kevin' phenomenon described so perceptively by Harry Enfield."

Six hundred children between six and 17 were studied to see how good they were at recognising facial expressions. There was a gradual improvement with age, interrupted only at puberty when both sexes began to regress. They recovered later.

Sadness and anger expressed in a face were emotions pubes-cent children seem to have great difficulty understanding. "For parents trying to manage their unruly adolescents - and this is as true for boys as it is for girls - one wonders whether they are understanding anything you are saying to them," Professor Skuse told the Festival, in Dublin. "It appears this is a function of the development of their brain at that time. It's not a cultural phenomenon, it's a real biologically based phenomenon from which fortunately they recover.

"There is that age of about 12, 13 or 14 when they seem completely oblivious to nuances of facial expressions but these same brain circuits are processing tone of voice. At six, there is a substantial difference between boys and girls. At school entry, 70 per cent of boys are worse than 50 per cent of girls."

Teachers trying to control unruly boys using subtle expressions, such as raised eyebrows, or a tone of voice may fail because boys are unable to read such signs, Professor Skuse said. "We're talking about a fairly substantial proportion of boys. One in five boys is worse than [most] girls."