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TV Ads Probably Won't Change Your Mind

A massive field experiment finds "issue ads" have small, short-lived effects.

Key points

  • In a recent study, researchers played ads about immigration and LGBTQ rights on over 31,000 people's TVs over three weeks.
  • Some of the ads had a small effect, reducing prejudice and increasing support for relevant policies while they were still airing.
  • Overall, the effects of the study's ads were extremely short-lived, mostly vanishing just one day after they stopped airing.

Since 1989, NBC has devoted a small portion of their airtime to education, public service announcements, and social awareness messages. The now-iconic "The More You Know" campaign has often featured stars of NBC shows to ... questionable effect. For example, here’s one ad with Matthew Perry from Friends.

Uh, okay. Seems like a nice clip for Perry’s demo reel to send to casting agents, but do ads like these, you know, work? Are they really changing any minds?

I’ve written before about the influential power of TV and specifically about how seeing members of different groups on TV can reduce prejudice. But watching an emotionally dynamic character for hours over a full season of a show is quite a bit different than watching a 30-second ad designed to change your mind about something.

A massive field experiment tests the influence of issue ads

A large-scale experiment published last month by political scientists Joshua Kalla and David Broockman tested this question out in a realistic way by actually showing people ads in their homes over several weeks. They focused on two issues: immigration and LGBTQ rights.

They targeted over 31,000 homes that had TV providers that enabled targeted ads to be broadcast to them. The homes were split into three roughly equal groups: two groups saw ads supporting immigration and one group saw ads supporting laws favoring LGBTQ rights. For example, the immigration ads featured first-person accounts from immigrants and one of the LGBTQ ads featured a Christian couple explaining that treating people how they wanted to be treated was required by their faith and that therefore nobody should be refused services for being LGBTQ. All the ads were professionally produced by organizations representing the relevant issue.

The ads aired over three weeks, an average of about 20 times in each house. At the end of the 3-week period, subjects were sent a survey that asked about lots of things, including issues related to the ads.

Watching the ads had small effects

The biggest effect resulted from one immigration ad that provided viewers with factual information, specifically that undocumented immigrants pay taxes. Survey results indicated that viewers of this ad were nearly five percentage points more likely to accept this fact as true than those who didn't see the ad.

But as far as changing minds, the effects were small to nonexistent.

Watching the LGBTQ rights ads did measurably decrease viewers' stated prejudices and increased their support for LGBTQ rights policies, but the effect was very small, an average of 0.036 standard deviations.

To understand how big of a change this was, suppose that people's initial average feelings of warmth toward LGBTQ groups on a 0-100 scale was 50 and that 95% of ratings fell in the range of 20 to 80. After being exposed to the ads for three weeks, an effect of 0.036 standard deviations is roughly equivalent to the average moving up by just 0.5 points. Very small, but potentially meaningful when multiplied by hundreds of thousands (or millions) of voters.

How long did these effects last?

Even for ads that did influence people's views, the effects were extremely short-lived.

To test this, the researchers sent the surveys to three different groups of respondents at different times: near the end of three-week ad period, one day after the ad period, or three days after.

The only group that showed any change in prejudice or support for LGBTQ rights policies was the one who received the surveys while the ads were still airing.

These results suggest that in order for these sorts of issue ads to be effective for influencing voters, for example, the ads should continue until voting has ended.

Do issue ads matter at all?

The More You Know.
Source: NBC

Is Matthew Perry telling viewers to stay in school with a smirk on his face going to make any difference? Who knows. But for ads like those in NBC's "The More You Know" campaign, this latest study offers some basis for optimism and some for pessimism.

First, it's clear that the effects of the ads were extremely short-lived, suggesting that influencing people's opinions through ads is not very effective (though it might be cost-effective relative to alternatives).

But there was evidence that people gained new knowledge from the ads, and they retained that knowledge even after the ads stopped airing. Sometimes learning something new can cause you to eventually change your mind about an issue down the road. Ads that seek to educate people may succeed long-term in gradually changing people's views by planting seeds that cause them to eventually end up changing their minds on their own.