A recent MarketingCharts analysis of Nielsen data found slightly declining rates of traditional TV consumption among youth, with steadier rates among older Americans. But as TV increasingly becomes part of a multi-screen experience, how many viewers are multitasking? New survey results from Deloitte indicate that 81% of Americans almost always or always engage in another activity while watching their home TV, with that figure rising to a high of 88% among 24-29-year-olds.

While this can detract from the TV experience, it can also enhance it. For example, Nielsen yesterday reported that it had found a correlation between Twitter buzz and TV ratings. Significant numbers of consumers around the world are indeed using their mobile devices to discuss TV programs on social networks as they watch them, even if Americans appear to be behind the curve in that regard.

Still, multi-screening behavior tends to favor unrelated over related content. The fear, of course, is that multi-tasking distracts viewers, with a negative effect for advertisers. That’s a real concern, given the wide variety of activities that youth engage in while watching TV, from browsing the web (42% of 14-23-year-olds) to text messaging (45% of that group), playing videogames (27% of 24-29-year-olds) and even reading (25% of 14-23-year-olds).

Another recent study, by Arbitron mobile, correspondingly finds that smartphone gaming and social networking activities peak during TV primetime hours. Among the 9 in 10 smartphone users who social network on their device, the hours between 7 and 10 PM counted as their peak usage period during weekdays. Those same hours were the peak times for the 8 in 10 smartphone gamers who participated in the hour-by-hour analysis. While smartphone activities peaking during primetime makes for a fun headline, it’s important to remember that even during their peak times, the average use per peak hour was only 1 minute and 17 seconds for gaming and 1 minute and 4 seconds for social networking.

Interestingly, while those activities almost certainly draw focus away from the TV, a media diary study conducted last year by the IAB and Ipsos MediaCT found that even while multitasking, consumers gave TV the majority of their attention. What’s more, a separate report released by the IAB and Econsultancy at the same time found that consumers who use multiple screens were more likely to recall advertisers on TV. The researchers suggested that this may be because people who have their second devices during commercial breaks are less likely to channel surf or skip the commercial break, leaving them aware, at some level, of the brands on the screen.

A new study from Gartner also looks at the rise of dual-screening from an optimistic perspective, arguing that dual-screeners will fuel the rise of social TV, with positive effects for content providers and advertisers. According to Michael Gartenberg, research director at Gartner: “The power of extending shared TV viewing, commenting and critiquing, combined with new ways of offering recommendations to friends, have already proved successful in existing social networks. Embracing and extending these activities to second-screen social TV experiences will drive stronger consumer loyalty, extend the value of brands and content properties and accelerate the curve of both content success and failure in terms of consumer adoption.”

About the Data: The Deloitte survey was fielded by an independent research firm from 11/8/2012 to 11/21/2012, and employed an online methodology among 2,129 US consumers. All data is weighted back to the most recent Census data to give a representative view of what US consumers are doing.

The Arbitron study was conducted during Q4 2012 with an opt-in sample of mobile consumers aged 18 and older.