http://www.dailymail.co.uk/news/article-1153583/Social-websites-harm-childrens-brains-Chilling-warning-parents-neuroscientist.html?ITO=1490 

An excerpt:

A study by the Broadcaster Audience Research Board found teenagers now spend seven-and-a-half hours a day in front of a screen.

Educational psychologist Jane Healy believes children should be kept away from computer games until they are seven. Most games only trigger the ‘flight or fight’ region of the brain, rather than the vital areas responsible for reasoning.

Sue Palmer, author of Toxic Childhood, said: ‘We are seeing children’s brain development damaged because they don’t engage in the activity they have engaged in for millennia.

‘I’m not against technology and computers. But before they start social networking, they need to learn to make real relationships with people.’