During the 2008 presidential debates, CNN unveiled their latest onscreen gimmick: A real-time graph depicting the averaged reactions of 32 supposedly undecided voters, who expressed favor or disfavor by turning handheld dials as they watched.

At the time, some psychologists wondered whether the graph could unduly influence how other viewers perceived the debate, potentially amplifying feelings in a handful of people across millions in the audience. The hypothesis was plausible, informed by decades of observations on decision-making and influence, but lacking hard data.

Some of that data now exists. In an experiment described March 31 in PLoS One, British psychologists secretly manipulated a similar onscreen graph broadcast during a Prime Ministerial debate. The results confirmed their fears.

"We were able to influence their perception of who won the debate, their choice of preferred prime minister and their voting intentions," wrote the researchers, who were led by Colin Davis and Amina Memon of the Royal Holloway University of London. "We argue that there is an urgent need to reconsider the simultaneous broadcast of average response data with televised election debates."

Along with the United States and United Kingdom, New Zealand and Australia also employ this technology, and it seems poised to spread. Audiences like it; the graph is eye candy, and intrinsically fun. After all, debates are more than opportunities to hear candidates present views and policy. They're intellectual boxing matches. People like keeping score.

There are, however, reasons to be suspicious of the graphs, known as "worms" in colloquial reference to their squiggling path across TV screens. Many studies describe how people are influenced by what others think, especially when they've yet to form an opinion of their own. It seems to be instinctive: Motivated to be accurate, we take others' assessments of reality into account, whether we want to or not. (As an example, just think how much easier it is to laugh at a joke when it's followed by laughter.)

A few studies have hinted more specifically at the worm's influence. One study of people watching a pre-taped version of American Idol found that audience feelings were shaped by what others reportedly felt. More strikingly, in a 2007 Political Science study of people watching tapes of 1984 Presidential debates between Walter Mondale and Ronald Reagan, the worm directly determined who people picked as winner.

But those studies were incomplete. In the grand scheme of things, American Idol just isn't that important, and a decades-old Presidential debate – watched by people who already know who won the election, and have probably forgotten most of the issues – isn't very realistic. Perhaps people would, when confronted with immediately important decisions involving substantive matters of policy, prove to be independent-minded and less likely to be swayed by others' opinions.

To test these propositions, Davis and Memon gathered 150 University of London students to watch the third and final 2010 UK election debate. Unbeknownst to the students, the broadcast worms were fake, added by the researchers with live video mixers.

Half the students watched a feed rigged to favor incumbent Prime Minister Gordon Brown. Of them, 47 percent said he won the debate, with challengers Nick Clegg getting 35 percent and David Cameron 13 percent. The other students watched a feed favoring Clegg. Of them, 79 percent said he won, with Brown and Cameron getting, respectively, 9 and 4 percent.

In short, the students proved every bit as susceptible as suspected. An informal next-day poll of 61 students on campus found that many thought Cameron – who scored worst in the study, disfavored by both fake feeds – actually won the debate.

>'The responses of a small group of individuals could, via the worm, influence millions of voters. This possibility is not conducive to a healthy democracy.'

Manipulative effect could also be measured even in test subjects who said they didn't pay attention to the worm, and couldn't remember whom it tended to favor. "The worm's influence may be quite difficult for viewers to discount," wrote Davis and Memon.

How long these impressions last is an unresolved question. They may dissipate quickly, or remain long enough to influence voting, especially if a debate is held shortly before an election. And while the worm used in the UK was visually larger than many, including the one used by CNN in 2008, it's possible that smaller cues actually have equal or greater effect.

Some psychologists have defended the use of realtime onscreen response data, arguing that it's empowering and provides a source of raw information, ostensibly free from spin. But asked in 2008 about the technology's potential, University of Nebraska political scientist Kevin Smith countered that "it could serve as a form of spin."

With feedback based on just a few people – CNN's 32-person sample was actually larger than some worm focus groups in the UK and Australia – one or two political partisans posing as good-faith participants could change a graph's average, potentially affecting the opinions of millions. Another potential skew could come from the group's makeup, which for small groups is less likely to represent the general public. And of course a biased media organization could intentionally skew participation.

But even without cynical manipulation, studies like this suggest that real-time onscreen feedback is fundamentally incompatible with the notion that voters ought to think for themselves.

"The responses of a small group of individuals could, via the worm, influence millions of voters. This possibility is not conducive to a healthy democracy," wrote Davis and Memon.

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Citation: "Social Influence in Televised Election Debates: A Potential Distortion of Democracy." By Colin J. Davis, Jeffrey S. Bowers, Amina Memon. Public Library of Science One, Vol. 6 No. 3, March 30, 2011.