During his campaign and presidency, Donald Trump has used Twitter to circumvent traditional media broadcasters and speak directly to the masses. He is particularly known for one specific tweet construction: he sets up a situation that he feels should inspire anger or outrage, then punctuates it with “Sad!” New research from New York University suggests a reason why this style is so effective: a tweet containing moral and emotional language spreads farther among people with similar political persuasion.

The study offered up “duty” as an example of a purely moral word, “fear” as a purely emotional one, and “hate” as word that combined the two categories. The research found that the use of purely moral or purely emotional language had a limited impact on the spread of a tweet, but the “presence of moral-emotional words in messages increased their diffusion by a factor of 20% for each additional word.”

The impact of this language cut both ways. Tweets with moral-emotional words spread further among those with a similar political outlook, and they spread less with those who held opposing views, according to the research published in the journal PNAS. The study looked at 563,312 tweets on the topics of gun control, same-sex marriage, and climate change, and rated their impact by the number of retweets each one received.

Righteous indignation, anyone?

Across all three topics, tweets that contained moral-emotional words were far more likely to induce “moral contagion” (a fancy way of saying they went viral) than tweets that lacked this sort of language. The type of emotion present also played a role. Tweets that used language associated with love or anger spread further than those associated with disgust and sadness. That would seem counterintuitive, given Trump’s success on Twitter, but it’s worth noting that his use of the word “sad” was often tied to expressions of anger or outrage.

The study concludes that there is an empirical basis to the argument that Trump’s tweets, which struck many longtime observers of politics as ill-considered and unhinged, helped to power his successful campaign. “It seems likely that politicians, community leaders, and organizers of social movements express moral emotions—of either positive or negative valence—in an effort to increase message exposure and to influence perceived norms within social networks,” the study reads. “Our work suggests that such efforts might pay off.”

The study notes that its scope has so far been limited to Twitter, and that research on the transmission of ideas across the much larger user base of Facebook is needed. Still, if the findings are validated by future testing, it would indicate that Trump may have tapped into a powerful social media dynamic — and the rest of us are in for an era of very temperamental political tweets.