Key Points:

Social networking websites such as Facebook and Twitter risk "infantilising" the adult minds of the mid-21st century, a leading neuroscientist says.

Children's experiences on social networking sites "are devoid of cohesive narrative and long-term significance," Lady Greenfield, professor of synaptic pharmacology at Lincoln College, Oxford, and director of the Royal Institution, told Britain's House of Lords.

"As a consequence, the mid-21st century mind might almost be infantilised, characterised by short attention spans, sensationalism, inability to empathise and a shaky sense of identity."

She said social network sites jeopardise users' ability to concentrate for more than a few moments on one thing, the Guardian reported.

"If the young brain is exposed from the outset to a world of fast action and reaction, of instant new screen images flashing up with the press of a key, such rapid interchange might accustom the brain to operate over such timescales. We will see such behaviours and call them attention-deficit disorder."

She called for an investigation into whether there was a correlation between "the near total submersion of our culture in screen technologies over the last decade" and the increase over the same period in the prescribing of drugs for such disorders.

She also warned against "a much more marked preference for the here-and-now, where the immediacy of an experience trumps any regard for the consequences. After all, whenever you play a computer game, you can always just play it again; everything you do is reversible".

She said identity could be eroded by "fast-paced, instant screen reactions, perhaps the next generation will define themselves by the responses of others".

Social networking sites could provide a "constant reassurance - that you are listened to, recognised, and important", she said, but the sites did away with conversations which were "far more perilous ... occur in real time, with no opportunity to think up clever or witty responses".

She said she feared "real conversation in real time may eventually give way to these sanitised and easier screen dialogues, in much the same way as killing, skinning and butchering an animal to eat has been replaced by the convenience of packages of meat on the supermarket shelf.

"Perhaps future generations will recoil with similar horror at the messiness, unpredictability and immediate personal involvement of a three-dimensional, real-time interaction."

Lady Greenfield said Facebook appealed to today's younger generations because "a child confined to the home every evening may find at the keyboard the kind of freedom of interaction and communication that earlier generations took for granted. But even given a choice, screen life can be more appealing.

"It is hard to see how living this way on a daily basis will not result in brains, or rather minds, different from those of previous generations."