In the past year, time-shifting of television content grew by almost two hours, averaging 13 hours per month, the study found. Viewers averaged nearly 134 hours of live TV viewing a month in 2013, down nearly three hours from 2012.
Television still remains central to media consumption, the study found, despite the increase in time-shifted viewing and streaming video through a computer or smartphone.
On average, American consumers own four digital devices, the report found. The majority of U.S. households own high-definition TV sets, Internet-connected computers and smartphones, while nearly half also own digital video recorders and gaming consoles.
The average consumer spends about 60 hours a week viewing content across various platforms, Nielsen found. Multitasking is common; 84 percent of smartphone and tablet owners say they use their devices as second screens while watching TV.
"It's an incredibly exciting evolution in the ways people are using devices to get media," said Megan Clarken, Nielsen executive vice president.
While sports events generated the most Twitter postings last year, more than 400 million, TV series also had impressive numbers. The top three: "Breaking Bad" with 6 million tweets, "The Walking Dead" with 4.9 million and "American Horror Story: Coven" with 2.9 million.
An offbeat survey finding: 40 percent of adults between the ages of 18 and 24 use social media in the bathroom.