Their inability to read non-verbal clues from those around them. Such a deficit can lead to all kinds of social problems because they won't catch the subtle clues about how others are reacting to them in face-to-face social situations.
In September 2008, when Nielsen Mobile announced that teenagers with cellphones each sent and received, on average, 1,742 text messages a month, the number sounded high, but just a few months later Nielsen raised the tally to 2,272. A year earlier, the National School Boards Association estimated that middle- and high-school students devoted an average of nine hours to social networking each week. Add email, blogging, IM, tweets and other digital customs and you realize what kind of hurried, 24/7 communications system young people experience today.How many times have we seen teens sitting off to one side during a family social gathering, busily tapping away at the keypads of the cell phones, texting friends rather than interacting with people in the same room. It isn't necessarily that the teens are being rude. Instead it's because they really don't know how to interact without that electronic crutch as an interface, be it a cell phone, computer, or Blackberry.
Unfortunately, nearly all of their communication tools involve the exchange of written words alone. At least phones, cellular and otherwise, allow the transmission of tone of voice, pauses and the like. But even these clues are absent in the text-dependent world. Users insert smiley-faces into emails, but they don't see each others' actual faces. They read comments on Facebook, but they don't "read" each others' posture, hand gestures, eye movements, shifts in personal space and other nonverbal—and expressive—behaviors.
So far my son has been able to avoid the 'need' for such an electronic crutch. For him a cell phone is nothing more than something you use to make a phone call. Beyond that it has no allure for him at all. While he does chat occasionally with friends on Facebook, he's rarely at it for more than a few minutes before he returns to what he was doing before the chat window opened. He much prefers to talk with his friends face to face.
So do I.