With American consumers watching an increasing amount of video content online every day, pre-roll, mid-roll and post-roll ads can reach a massive audience. However, just as TV watchers can switch channels or leave the room at commercial breaks, online viewers can easily click on a new browser tab and mute their device when they see an ad appear on the screen.

The key to ensuring online video ads are being watched is by creating contentstimulating enough to make viewers want to watch the clip, according to Harvard Business School’s Thales S. Teixeira. The assistant professor’s experimental research suggest advertisers can keep consumers’ attention by evoking certain emotional responses, according to HBS Working Knowledge.

Triggering emotion
Teixeira’s team of researchers enlisted 58 individuals to watch four-minute sitcom clips followed by a series of advertisements. Fourteen of the 28 ads were deemed provocative by the researchers, who expected them to evoke joy or surprise in the viewers. The rest of the ads were labeled as emotionally neutral. When an ad appeared on-screen, participants could either skip to the next one or watch it completely.

Researchers videotaped viewers’ expressions and an infrared eye tracker to measure eye movements throughout the experiment to determine emotional responses and whether their eyes were fixed or moving.

“We found that people’s attention patterns on-screen were different depending on the emotion they were feeling,” Teixeira told HBS Working Knowledge. “So during the ad, your eyes move differently on the screen, depending on whether you’re surprised or you’re joyful.”

The element of surprise
Researchers found the most successful ads were those that contained a big surprise or punch line. The challenge though is keeping viewers’ attention long enough for them to see the surprise and making their feeling of intrigue last.

The most successful ad was for a beer brand. In the commercial, office workers to contribute to a swear jar every time they say something obscene. When they learn the money in the jar will go toward the purchase of beer, the characters begin swearing profusely. Each curse word is bleeped so the commercial becomes a succession of bleeps, which invokes surprise at first and then humor, or joy, in the eyes of the viewer.

In a recent blog post for MediaPost, P.J. Bednarski pointed out the immediacy of surprise required in video ads. “‘Wait for it, wait for it’ doesn’t work with online ads. Because people won’t wait for it,” hewrote.