Vain generation: A top Oxford scientist has warned that repeated exposure to social networking websites could harm users.

Facebook and Twitter have created a generation obsessedwith themselves, who have short attention spans and a childlike desire for constant feedback on their lives, a top scientist believes.

Repeated exposure to social networking sites leaves users with an 'identity crisis', wanting attention in the manner of a toddlersaying: 'Look at me, Mummy, I've done this.'

Baroness Greenfield, professor of pharmacologyat Oxford University, believes the growth of internet 'friendships' – as well as greater use of computer games – could effectively 'rewire' the brain.

This can result in reduced concentration, a need for instant gratificationand poor non-verbalskills, such as the ability to make eye contact during conversations.

More than 750million people across the world use Facebook to share photographs and videos and post regular updates of their movements and thoughts. Millions have also signed up to Twitter, the 'micro-blogging' service that lets members circulateshort text and picture messages about themselves.

Baroness Greenfield, former director of research body the Royal Institution, said: 'What concerns me is the banalityof so much that goes out on Twitter.

'Why should someone be interested in what someone else has had for breakfast? It reminds me of a small child (saying): “Look at me Mummy, I'm doing this”, “Look at me Mummy I'm doing that”.

'It's almost as if they're in some kind of identity crisis. In a sense it's keeping the brain in a sort of time warp.'