The average US Internet user spends three hours a day online, with much of that time devoted to work and more than half of it to communications, according to a survey conducted by a group of political scientists.
The survey found that use of the Internet has displaced television watching and a range of other activities. Internet users watch television for one hour and 42 minutes a day, compared with the national average of two hours, according to Norman Nie, director of the Stanford Institute for the Quantitative Study of Society, a research group that has been exploring the social consequences of the Internet.
"People don't understand that time is hydraulic," he said, meaning that time spent on the Internet is time taken away from other activities.
A 2000 study by the researchers that reported increasing physical isolation among Internet users created a controversy and drew angry complaints from Internet fans who insisted that time they spent online did not detract from their social relationships.
However, the researchers said they had now gathered further evidence that showed that, in addition to its impact on television viewing, Internet use has lowered the amount of time Americans spend socializing with friends and even sleeping.
According to the study, an hour of time spent using the Internet reduces face-to-face contact with friends, co-workers and family by 23.5 minutes, lowers the amount of time spent watching television by 10 minutes and shortens sleep by 8.5 minutes.
The researchers acknowledged that the study data did not answer questions about whether Internet use itself strengthened or weakened social relations with one's friends and family.
"It's a bit of a two-edged sword," Nie said. "You can't get a hug or a kiss or a smile over the Internet." Many people are still more inclined to use the telephone for contact with family, he said.
The latest study also found that online game playing has become a major part of Internet use.
Overall Internet use broke down as 57 percent devoted to communications like e-mail, instant messaging and chat rooms, and 43 percent for other activities including Web browsing, shopping and game playing. Users reported that they spent 8.7 percent of their Internet time playing online games.
Another finding was that even though the Internet is widely employed for communications, users spend little of their online time in contact with family members.
Of the time devoted to communication, just one-sixth was spent staying in touch with family members, much less than the time spent on work-related communications and contact with friends.
The study found that as much as 75 percent of the US population now has access to the Internet either at home or work.
"It is remarkable that this expansion of use has happened in just a decade since the invention of the Web browser," Nie said. That rate of growth is almost as fast as the spread of the telephone and is impressive because the computer is more complicated to use, he said.
The study, titled "What Do Americans Do on the Internet?" also found that junk e-mail and computer maintenance take up a significant amount of the time spent online each day.
Respondents reported spending 14 minutes daily dealing with computer problems. That would suggest that Internet users spend a total of 10 work days each year dealing with such problems.