the majority of experiments that have looked directly at the effects of the internet, video games and online social networking have actually found significant cognitive benefits. Video games improve visual attention and memory, Facebook users have more friends (in real life, too) and preliminary evidence suggests that surfing the web "engages a greater extent of neural circuitry...[than] reading text pages."
Now these studies are all imperfect and provisional. (For one thing, it's not easy to play with Google while lying still in a brain scanner.) But they certainly don't support the hypothesis that the internet, as Carr writes, is turning us into "mere signal-processing units, quickly shepherding disjointed bits of information into and then out of short-term memory."
via scienceblogs.com