communication since man first picked up an animal horn and realized his voice carried farther if he shouted into it. These days, Twitter feeds, Facebook updates and emails allow us to “socialize” with headphones on. A century ago, when telephones were a revolutionary communication device, companies marketed them exclusively for business purposes and only later as a practical addition to the home, The Times reported.

But almost immediately people realized the potential to talk to friends or family who were farther away than the next room.

“The phone companies tried to stop that for about 30 years because it was considered improper usage,” Claude S. Fischer, a sociology professor at the University of California, Berkeley, told The Times.

These days fewer and fewer people pick up the phone, except perhaps to call their mother. And forget about voice mail messages. “I don’t check these messages very often,” warns the voice mail of Dr. Fischer, who has written a book on the history of the telephone. Instead, he urges callers to send an e-mail.

“I remember when I was growing up, the rule was, ‘Don’t call anyone after 10 p.m.,’ ” Jonathan Adler, an interior designer in New York, told The Times. “Now the rule is, ‘Don’t call anyone. Ever.’ ”

In the last five years, adults have cut back on their use of the telephone ? land line, mobile, voice mail and all, The Times reported. According to Nielsen Media, spending on text is expected to bypass voice within three years.

But texting with just one person is not enough for some, so developers are creating messaging services that allow a group conference call or chat room via text message, The Times reported.

“Try having a conversation on Twitter or Facebook with you and 500 of your closest friends,” Steve Martocci, a founder of GroupMe, one of the new applications, told The Times. “They are limited by their broadness. People can’t say what they want or express themselves.”

GroupMe limits the number of people allotted to a single conversation to 25, although users can participate in as many groups as they like.

For those locked up in jails, a simple phone conversation can be a lifeline. Though cellphones are illegal in all state and federal prisons in the United States, they get in by the thousands.

Prison officials say smartphones allow prisoners to engage in criminal behavior behind bars, using Internet access to orchestrate all manner of crimes, gang violence and drug trafficking.

Or, simple conservation.

Mike, an inmate in Georgia, said he used his phone to stay in touch with his son. “When he gets off the school bus, I’m on the phone and I talk to him,” he told The Times in an interview on his contraband cellphone. “When he goes to bed, I’m on the phone and I talk to him.”

But inmates are more likely to successfully re-enter society if they maintain relationships with friends and families, said David Fathi, director of the National Prison Project at the American Civil Liberties Union.

“It shows that even if they are closed institutions, prisons are still part of the larger society,” Mr. Fathi told The Times. “They can’t be forever walled off from technological changes.”


TOM BRADY