Even in music, though, we found the same result. Music reviews that used more present-tense verbs were more persuasive.

Indeed, when we analyzed the movies, we found that those which interspersed highly positive moments with strongly negative ones were more successful. Movies that repeatedly traversed from the lowest of emotional lows to the highest of emotional highs, and back again, were liked more.

It turns out that these differences in certainty have an important impact on sustained attention. Looking across thousands of pieces of content, we found that uncertain emotions encouraged engagement…

Uncertainty led readers to stick around to resolve what they didn’t know.

Second, emotional language is a powerful tool to increase engagement.

But those two or three words made a big difference. Rather than hurting their motivation, praising the students’ process, or how hard they had worked, encouraged them to keep going.