Liza Colburn uses her cellphone constantly, the New York Times reports. She taps out her grocery lists, records voice memos, listens to music at the gym, tracks her caloric intake and posts frequent updates to her Twitter and Facebook accounts. The one thing she doesn’t use her cellphone for? Making calls. “I probably only talk to someone verbally on it once a week,” said Mrs. Colburn, a 40-year-old marketing consultant in Canton, Mass., who has an iPhone. For many Americans, cellphones have become irreplaceable tools to manage their lives and stay connected to the outside world, their families and networks of friends online. But increasingly, by several measures, that does not mean talking on them very much.