How Large and Long-Lasting Are the Persuasive Effects of Televised Campaign Ads?

A 2011 study published in the American Political Science Review, “ Results from a Randomized Field Experiment,” makes a novel contribution to the research literature by studying the phenomenon from inside an ongoing Texas gubernatorial campaign (incumbent Rick Perry in 2006.) The researchers, from Yale, the University of Maryland and the University of Texas at Austin, persuaded campaign operatives to allow $2 million in campaign advertising to be spent in ways that ensured randomness in the volume, timing and location of radio and television commercials in certain markets. The study also involved surveying voters in these ad markets and assessing how their views persisted over time.

The study’s findings include:

• “The maximum dosage of television advertising apparently boosted [the candidate’s] relative standing by approximately six percentage points. Advertising thus appears to have the capacity to induce a substantial shift in vote preferences. The variance in radio advertising volume is much smaller, and the standard errors are therefore larger.”
• “TV ads exert a strong and significant effect in the current week, smaller and statistically equivocal effects a week later, and no effects thereafter…. Overall, the analysis of dynamics suggests that the effects of TV, although powerful, were short-lived. Not only did they dissipate before Election Day in November, they vanished before the March primary.”
• The study does not support a prominent theory about advertising effects and voter learning; the findings contradict the notion that, though viewers may forget the particulars of a message, some effects may endure and viewers may nevertheless learn and absorb new attitudes at a deeper level.
• In contrast, the results appear to show that the principal way ads affect voters is by “priming” them and temporarily shifting the evaluative criteria by which they judge candidates: “The precise way in which priming occurs is subject to alternative but complementary explanations. One possibility is that the ads made people more likely to place certain considerations in working memory. Another is that the ads increased the weight that people accorded these considerations when evaluating the candidates. Whether these ads jogged memory or focused attention or both, they do not appear to have propagated enduring beliefs.”