The CIA, the FBI and even some members of local law enforcement are trained to spot what are known as micro-expressions, a slight lip raise, a glance off, any small, almost imperceptible movement that shows what a person is really feeling.
Mix in videotape and some fancy software, and a computer will do it for you, picking up simple movements in key areas of the face like the forehead, eyes, lips and jaw. The computer program then translates those movements into emotions like surprise, fear, disgust, anger or pride.
Put it all together and you get a snapshot of how the candidate himself was feeling during the first presidential debate of 2012.
Squirreled away in a computer science lab on the campus of Purdue University, Chris Kowal analyzes 395 specific points on the human face.
"Overall, Mitt Romney was much more expressive," Kowal said.
Those expressions can give insight, says the professor. His analysis found, during the debate, anger, scorn and pride in himself were the most common emotions shown by Mitt Romney.
Barack Obama frequently showed pride, happiness, but also sadness. That may be the computer picking up on the president's frequent downward gazes.
"He didn't connect on an emotional level with those voters because he himself wasn't experiencing the emotions that they were looking for," Kowal said.
Experts say those subtle emotional tells play out in how the candidates are perceived.
Fifty-eight million people watched the debate on television. Adding importance to first impressions: 10 million people shared their take on Twitter.
"The social media circulates the contents of the debate much faster," said Northwestern University's David Zarefsky. "They make it a bit more irreverent, and they are more willing to take down candidates a peg."
Les Lynn runs Chicago Debate Committee, a program for 76 high schools. He says President Obama forgot the first rule of debating: engage your opponent.
"Barack Obama has to view the debate different. He's got to go all in," Lynn said. "He's got to look at it as a contest in order to be re-elected. He didn't. I think he was looking for a draw."
Back on the Purdue campus, the computers found both men shared the same shortcoming Wednesday night.
"That emotional connection is perhaps the biggest deficit that both of these candidates are facing," said Kowal.
The campaigns themselves are also analyzing the debate, determining what worked and what didn't.
President Obama's national campaign spokesman told ABC7 Thursday the president knows he needs to come out swinging harder next time.
Keep in mind, at this stage of the game, Mitt Romney and Barack Obama are competing for undecided voters, who will likely make the difference in battleground states, which according to the most recent ABC poll make up just 6 percent of the electorate.