Over the last two years, the shift has been drastic. Among children under 2, the survey found, 38 percent had used mobile devices like iPhones, tablets, or Kindles — the same share as children 8 and under who had used such technology in a similar survey two years ago.

Tablets, in particular, have become far more common. Forty percent of families now own tablets, up from only 8 percent two years ago. And this year’s survey found that 7 percent of the children had tablets of their own.