In the U.S., at least three of every four people now own a smartphone. And one estimate suggests that Americans touch their mobile devices more than 2,600 times a day on average. But are all those pings and buzzes, scrolls and swipes worrisome for health and society?

Initial data from a $300-million study by the National Institutes of Health, for example, now provides evidence that a child's brain may indeed develop differently with heavy use of digital devices. Those of us whose brains matured before the first iPhone came to market in 2007 may also be vulnerable to mental changes.

Turns out, the more tethered we are to our phones, the harder it is to think deeply, attentively and conceptually — not to mention remember basic information.