They are notoriously menacing: groups of teenagers who slouch on street corners, trainered feet defensively apart, hoodies pulled low over their eyes.
But young people often hang out on the streets not to threaten others, but to keep safe and avoid trouble, say researchers.
And, equally, those who stay indoors and spend all their free time on the internet are not geeky loners, but are developing vital communication skills.
A study by the Joseph Rowntree foundation, a social-policy charity, reveals that teenagers in disadvantaged areas often chose to be with large numbers of friends to protect themselves from aggressive adults with drink or drug problems.
They said they also needed to protect themselves from gangs, which are seen as an immediate threat to their safety, and present a long-term risk of drawing them into crime and anti-social behaviour.
"Friends helped provide knowledge of risks and safety, support and reciprocal monitoring; though there was a danger that moving in groups was interpreted as threatening by adults or other children," the research says.
More than 250 children were questioned for the study, conducted by academics at Glasgow university. More than 230 parents were also interviewed, all living within four deprived areas of Glasgow.
Groups of teenagers developed a range of strategies to avoid difficulties.
Most kept a low profile, avoiding people and places known to be troublesome.
Parents and children often categorised different parts of their neighbourhood as safe or unsafe. Children even designated certain spaces as safe only on certain days or times, dependent on who would be there.
But parents were generally unaware of the importance of friends in ensuring that young people felt safe.
They saw large groups of teenagers as threatening, and preferred their children to attend organised activities instead.
Research has also shown that teenagers who prefer to stay indoors are similarly misunderstood by adults.
Academics at Northwestern university, in Chicago, said that adults often fear that their children spend too much time on the internet, and are losing the skills of social interaction and community involvement with other people.
But in fact, teenagers are able to form effective online communities, electing leaders and consulting with others for ideas.
Researchers spent seven years studying an online community of 3,000 people, between the ages of 10 and 16.
They conclude: "The internet is making a diversity of communities possible.
There is an online community for every kind of young person, where children may meet and discuss their lives, feelings and their view of the world around them "We believe that adolescents may be constructing their own styles of leadership and community involvement."
For more information, see www.jrf.org.ukand for more details on the Northwestern university study, email firstname.lastname@example.org