How the 'digital cocoon' can affect you
Jan, a mother of teenagers, talked to Rosen about her husband who, she says, used to go regularly with her to the cinema and to dinner with friends.
Now "he's always on the computer updating his status and commenting on articles... In a short time he has gone from Mr Social to Mr Online".
Rosen says the mobility of new devices that bring us within ever closer reach to networks of friends has added to a "digital cocooning" effect, causing many people to become socially withdrawn from the real world.
There is better news for the shy, who find, unsurprisingly, that they are more able to communicate online than off and tend to have more friends on social networking sites than their more socially confident "friends".
Rosen remembers a time when he would "sit with a good book and curl up on a couch with a coffee and read for two hours straight". He adds: "I find that impossible now." You, too, may find that unread books pile up on your shelves, that magazine articles have become more difficult to finish, or that you cycle between tabs on your web browser when you should be working.
The researcher surveyed more than 1,300 people of different ages and found the younger participants were much more willing and able multitaskers. But, he writes, "the more tasks we take on... the more our brain gets stressed and overloaded, and the worse we do at all of the tasks." There is no multitasking, Rosen says, only "task-switching", and it isn't productive.
Rosen admits he shows signs of obsessive behaviour around Words with Friends, the Scrabble-inspired smartphone game. "I've conditioned myself to turn it off at night but I'm still up at midnight refreshing it in case anybody's played a move when I know they haven't."
Whether it's repeatedly checking your inbox or Facebook, Rosen blames this sort of behaviour on the "undercurrent of anxiety that if we don't check in we may be missing out on something".
"Disconnectivity anxiety" leads to worry and even physical distress. To combat this, Rosen suggests using your WMDs less. "Train your brain to stop thinking about your technology. Take a 10-minute break every two hours and 'reset'. Go stare at a tree, listen to music, laugh."