Robert McGivern and his team of neuroscientists at San Diego State University found that as children enter puberty, their ability to quickly recognise other people's emotions nosedives. What's more, this ability does not return to normal until they are around 18 years old. McGivern reckons this goes some way towards explaining why teenagers tend to find life so unfair, because they cannot read social situations as efficiently as others.
Previous studies have shown that puberty is marked by sudden increases in the connectivity of nerves in parts of the brain. In particular, there is a lot of nerve activity in the prefrontal cortex. "This plays an important role in the assessment of social relationships, as well as planning and control of our social behaviour," says McGivern.
He and his team devised a study specifically to see whether the prefrontal cortex's ability to function altered with age. Nearly 300 people aged between 10 and 22 were shown images containing faces or words, or a combination of the two. The researchers asked them to describe the emotion expressed, such as angry, happy, sad or neutral.
The team found the speed at which people could identify emotions dropped by up to 20 per cent at the age of 11. Reaction time gradually improved for each subsequent year, but only returned to normal at 18 (Brain and Cognition, vol 50, p 173).
During adolescence, social interactions become the dominant influence on our behaviour, says McGivern. But at just the time teenagers are being exposed to a greater variety of social situations, their brains are going through a temporary "remodelling", he says. As a result, they can find emotional situations more confusing, leading to the petulant, huffy behaviour adolescents are notorious for.
But this may only be true for Western cultures. Adolescents often play a less significant role in these societies, and many have priorities very different from their parents', leading to antagonism between them. This creates more opportunity for confusion. "One would expect to observe a great deal more emotional turmoil in such kids," he says.
New Scientist issue: 19th October 2002
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