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A new study by Yale University has shown that, regardless of content, context, or audience, pricey commercials during US presidential campaigns do little to persuade voters, political scientist Alexander Copock said in the September 4 issue of ScienceDaily.

The study, published Sept. 2 (September 3, 2020 in Manila) in the journal Science Advances, measured the persuasive effects of 49 high-profile advertisements from the 2016 presidential campaign on a nationally representative sample of 34,000 people through a series of 59 randomized experiments. Expanding on prior research suggesting that political ads have little impact on voters' preferences, the study shows that those weak effects are consistent irrespective of a number of factors, including an ad's tone, timing, and its audience's partisanship. They found that, on average and across all variables, the ads moved a candidate's favorability rating respondents only 0.05 of a point on the survey's five-point scale, which is small but statistically significant given the study's large size, note the researchers. The ads' effect on whom individuals intended to vote for was smaller still -- a statistically insignificant 0.007 of a percentage point.

"There's an idea that a really good ad, or one delivered in just the right context to a targeted audience, can influence voters, but we found that political ads have consistently small persuasive effects across a range of characteristics," said Coppock, an assistant professor of political science in the Faculty of Arts and Sciences. "Positive ads work no better than attack ads. Republicans, Democrats, and independents respond to ads similarly. Ads aired in battleground states aren't substantially more effective than those broadcast in non-swing states."

Coppock and his co-authors -- University of California-San Diego political scientist Seth J. Hill and UCLA political scientist Lynn Vavreck -- conducted the study throughout the 2016 presidential primaries and general election. Over 29 weeks, a representative sample of Americans was divided at random into groups and assigned to watch campaign advertisements or a placebo advertisement -- a car-insurance commercial -- before answering a short survey.

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