PARENTS may hate it but the maddening behaviour of teenagers, ranging from mood swings to binge drinking and worse, is actually essential to their development, say scientists.
Teenage traits such as moodiness, and the foolish behaviour depicted in The Inbetweeners, below, are inevitable, scientists say
They suggest that adults should stop branding teen traits such as aggression, impulsiveness, a love of novelty and a disregard of rules as antisocial.
Instead, such behaviour should be respected as the time in a person's life when they are at their peak of adaptability, ready to seek out new challenges, disregard dangers and take risks on relationships.
"Heightened risk-taking . . . during adolescence is likely to be normal, biologically driven, and, to some extent, inevitable," said Laurence Steinberg, professor of psychology at Temple University in Philadelphia, in a recent paper. "There is probably very little we can or ought to do . . . this is a developmental shift that likely has evolutionary origins."
Such assertions are a far cry from the traditional view of teenagers as immature, prone to dangerous emotions and in constant need of monitoring and control by adults.
In The Winter's Tale, a Shakespeare character suggests that youths between 10 and 23 years old cared for little except "getting wenches with child, wronging the ancientry, stealing, fighting". Freud suggested adolescents were tortured by psychosexual conflict.
Modern scientists are, however, taking a different view. Teenagehood, they suggest, is a phase that has been honed by evolution to produce exactly the right behaviour to survive in a tough world.
Furthermore, although the teen years are now seen as a transition to a long adulthood, the reality for most of our species' existence has been that most people died before the age of 35. The teenage years were those in which most people faced survival on their own - often also becoming parents.
Professor B J Casey, a neuroscientist at Weill Cornell graduate school of medical sciences in New York, who has used brain imaging and other techniques to probe teenage development, says in an interview in National Geographic magazine: "We're so used to seeing adolescence as a problem. But the more we learn, the more adolescence starts to seem like a highly functional, even adaptive period. It's exactly what you'd need, to do the things you have to do then."
The idea that teenagehood is a special, rather than a blighted, part of the human lifespan, can be traced back to a series of studies carried out in the 1990s by the National Institutes of Health in America. Its scientists used the then new brain-scanning technologies such as MRI to monitor 100 young people as they grew up.
Until then, it had been thought that the brain changed little after childhood but what emerged was revolutionary, showing that human brains underwent profound changes during teenagehood.
Many nerve fibres grew longer, acquiring more connections and extra insulation - greatly improving the speed and volume of the information carried. The same studies showed that teenage brain growth lasted about a decade, only finishing in the early twenties.
Back then, many researchers concluded that such "unfinished" brains were inherently defective, linking this to teenage risk-taking and other "antisocial" behaviour. It is this idea that Steinberg, Casey and others are challenging. They say evolution would never have let humans develop behaviour that undermined their chances of surviving.
What do such findings mean for parents, teachers and others involved with teenagers?
Steinberg suggests it is largely pointless to expect teenagers to act in a way that adults would see as wise. Instead adults should be less judgmental and more practical. "More than 90% of all [ American] high-school students have had sex, drug and driver education in their schools, yet large proportions of them still have unsafe sex, binge drink, smoke and drive recklessly," he said.
"Strategies such as raising the price of cigarettes, more vigilantly enforcing alcohol laws and expanding adolescents' access to contraceptive services would likely be more effective in limiting adolescent smoking, substance abuse, pregnancy and automobile fatalities than strategies aimed at making adolescents wiser, less impulsive or less short-sighted," he said. "Some things just take time to develop, and, like it or not, mature judgment is probably one of them."