In the first February Democratic primary debate, candidates had another chance to pitch their ideas to potential voters. Viewers pay attention not only to what they say, but also to how they say it. The way presidential hopefuls move can affect how dynamic and memorable they appear to voters.

Experts weigh in on how candidates’ gestures vary and what they conveyed in past debates.

Sen. Bernie Sanders and President Trump, antiestablishment figures who want to convey frustration with Washington, use bigger, more dramatic gestures than other candidates.

“With both of them, notice how their hands are up high and coming down. So they’re making themselves appear bigger,” said Patrick Stewart, a political scientist at the University of Arkansas who studies emotion and nonverbal communication. “When we’re looking at Donald Trump and we’re looking at Bernie Sanders, they’re angry, and they’re angry for their followers—it’s their niche.”

Still, there are some differences. Mr. Trump’s gestures are fairly controlled and consistently emphasize his words, according to Dana Carney, director of the Institute for Personality and Social Research at UC Berkeley and an associate professor. She also noted that a common gesture the president uses is the OK symbol, which may be a way to emphasize being precise or to literally convey that what he is saying is “OK.”