The Nielsen Co. said Monday that people who multitask this way spent an average of three and a half hours doing so in December. That's up sharply from the two hours, 29 minutes that Nielsen reported only six months earlier.
The percentage of TV viewers who do this isn't going up that fast. That increased by 57 percent to 59 percent during the same period. But those who are doing it spend much more time at it.
Television executives have pointed to this trend to help explain why big events like the Oscars, Grammys and pro football playoffs have been doing so well in the ratings - people watching and making comments to their friends through social Web sites like Twitter and Facebook.
Nielsen attributed the continued rise in TV viewing to many factors: more convenience (such as DVR), a higher quality experience (high-def and flat-screen TVs) and the prevalence of digital delivery.
According to the study, most TV viewing continues to occur in primetime hours (8 - 11 p.m.) while most online video viewing lasts from about noon to 6 p.m., peaking at 4 p.m.
According to the study, in the fourth quarter of 2009:
-People over the age of 65 spent the most time watching traditional TV, with that demographic watching 47 hours a week.
-People aged 35-49 were the heaviest Internet users, going online six and a half hours a week. However, people aged 18-24 spent the most time watching video on the Internet: 39 minutes per week.
-People aged 12-17 spent the most time watching video on a mobile phone: 21 minutes per week.