Voters watching tonight’s highly anticipated debate between Kamala Harris and Donald Trump should look for signs of emotional mishmash on both their faces, a leading expert on microexpressions tells The Daily Beast.

Microexpressions are “the universal facial expressions of our species,” explained expert Annie Särnblad, meaning they are universal to humans, despite cultural and regional differences. That’s also what makes them so difficult to hide, she said, adding that “they precede the thought process.”

“They are involuntary and last only a fraction of a second.”

Särnblad, who previously analyzed Harris’ CNN interview, has a master’s degree in cultural anthropology and is also certified in the Facial Action Coding System (FACS). Tonight, Särnblad will analyze exclusively for the Daily Beast what micro-expressions she sees on the candidates’ faces.

In a televised debate, “a lot is at stake,” says Särnblad. “So we will pay attention to whether the facial expressions match the words, because the micro-expressions precede the thought process.”

“Remember, (microexpressions) tell you what they feel. Not what they think,” Särnblad said. “For example, if I say, ‘I hate broccoli’ and show the microexpression of disgust, it makes sense because I’m talking about something really negative.”

However, there can often be a noticeable discrepancy when someone tries to hide their feelings by using positive words but displaying negative micro-expressions.

She added: “Even when I work with my clients to prepare them for high-stakes public debates or negotiations, I try to get them to focus on answering the questions they’re being asked. We all know the trick of deflecting and answering the question you wish you had been asked instead of answering honestly. But I think the public is smart enough to see through that.”

Särnblad said she would also observe what the candidates do to calm themselves under pressure.

“One of the universal properties of body language is that we humans touch our skin when we get nervous,” Särnblad said. “One of the really interesting properties of politicians is that they use the steeple self-soothing technique, which is actually a way of calming yourself down by touching your skin.”

She added: “It looks like a powerful position, but it’s actually designed to calm the nervous system.”

Ahead of the debate, the Harris camp reportedly called for microphones to remain on while the opposing candidate answered a question.

Trump, who is 6’3″, has asked that no boxes or cherry pickers be allowed during the event. This could result in him towering over Harris (reportedly 5’2″) if they are allowed to walk around the stage – as Trump famously did during his debate against Hillary Clinton in 2016.

Annie Särnblad is the author of three books: Diary of a Human Lie Detector: Facial Expressions in Love, Lust, and Lies, The Facial Expressions Glossary: ​​​​Business Version, and the recently published Annie and the Secret Language of Faces.

The above videos were produced by Emma Särnblad.