Congresswoman Michele Bachmann’s body language made her messaging stand out in a recent debate among other GOP presidential candidates. (EMMANUEL DUNAND/AFP/GETTY IMAGES)

This piece is part of a roundtable with Post columnist Steven Pearlstein and three of our On Leadership expert contributors — Theresa Amato, D. Michael Lindsay and Carol Kinsey Goman — about Michele Bachmann’s leadership credentials and challenges.

Researchers call it “baby face bias”.

Last week’s Republican debate was the first time this primary season that GOP presidential contenders went head to head before a national audience, and the coverage that followed showed Rep. Michele Bachmann emerging from the pack. Of course what she said played a major role, but perhaps what grabbed viewers’ attention even more was how she said it.

Today’s political figures are fully aware of, and heavily coached on, the impact of body language. They know that, when it comes to nonverbal cues, everything matters: gender, age, skin color, hair style, attractiveness, height, clothing, facial expressions, hand gestures, posture—audiences judge it all. Superficial? Maybe. But this potent, and often unconscious, process is also hardwired in the human brain. Two sets of nonverbal signals are especially important for presidential candidates to project: warmth and authority. Warmth cues project likeability and candor, and authority cues denote power and status. The most appealing politicians are those whose body language reflects both sets of signals, which Bachmann did—and more successfully than anyone else on stage that night.

Authority is nonverbally displayed through height and space, and Bachmann made up for her smaller physical stature by wearing high heels, standing tall and keeping her shoulders back. She also used arm and hand gestures that were sweeping and commanded space. Like Rick Santorum, Herman Cain and Newt Gingrich, Bachmann used a popular political hand gesture to emphasize her main points. All of them squeezed their fingers against their thumbs to make an “ok” type of gesture, and then rhythmically kept a beat as they spoke. This “finger tip touch” sends an image of authority but not aggression.

Carol Kinsey Goman is an author and body language expert. Her books include “The Nonverbal Advantage” and “The Silent Language of Leaders.”

Yet unlike the other candidates, Bachmann also had the warm-cue advantage of “baby face bias,” a term used to describe the tendency found in human beings across all age ranges and cultures to read innocence and candor in faces with features that are similar to an infant’s. (These characteristics include a round head, big eyes, small nose, high forehead and short chin.) Add to that Bachmann’s gestures with open palms, which signaled candor and inclusion, and her smile. Research from Duke University proves that we like and remember those who smile at us, though using such cues deliberately but moderately is one of the most difficult balances for candidates to strike.

As Harvard Business School professor Teresa Amabile described in an aptly titled article, “Brilliant But Cruel,” we often see competence and warmth as being negatively related—warm leaders don’t appear as intelligent or skilled as those who are sterner, and tough leaders are judged far less likeable.

This was one of the main body language errors made by Sarah Palin, another subject of baby face bias. In the 2008 vice presidential debate, she overused  warm gestures, especially winks and smiles, which in turn lowered the perception of her authority and power.

Bachmann’s only body language error may have been a cosmetic one: her decision to wear false eyelashes. Researchers who analyze politicians’ blink rate find that fast blinkers rarely win elections. Blink rates increase under stress, and they signal a candidate’s nonverbal reaction to pressure. While Romney has a fairly low blink rate, Bachmann has a moderately high one, and the false eyelashes she wore during the debate made her blinks much more obvious than those of her competitors.

Romney had another immediate nonverbal advantage: He was one of the tallest people on stage. This may seem a trivial fact, but we unconsciously associate leadership characteristics with height. The effects of this are seen not only in politics but also in the boardroom. In the U.S. population, 14.5 percent of men are over six-feet tall, but with CEOs of Fortune 500 companies that statistic climbs to 58 percent.

In The Political Brain, Drew Westen writes that, after party affiliation, the most important predictor of how people vote is their emotional reaction—or gut feeling—toward the candidate. That’s why body language plays a key role in political debates. Most of the emotional component of a message is not in what is being said, but rather in how it is said and how the politician looks when he or she says it.

The major story of the first televised presidential debate in 1960 became the photogenic appeal of John F. Kennedy versus the sickly look of his opponent, Richard Nixon. Several factors contributed to the poor image of Nixon: His ill health leading up to the debate had resulted in a drastic weight loss. He refused to wear makeup, although his illness had left him with a pallid complexion. He wore a suit that blended in with the light grey color of the set’s backdrop. And, to make matters worse, the cameras caught Nixon wiping perspiration from his forehead while Kenney was pressing him on the issues.

As for Kennedy, he excelled in front of the camera. A polished public speaker, Kennedy appeared young, athletic, handsome and poised. And Kennedy looked directly at the camera when answering questions (rather than at the journalists who asked them), which made viewers see him as someone who was talking directly to them and giving straight answers.

Radio listeners, who heard the debate but hadn’t seen it, gave the victory to Nixon. But a large majority of television viewers recognized Kennedy as the winner.

Fast forward 50-plus years and, for better or worse, the same dynamics influence our political process today. The sole female candidate among Republican contenders walked on stage and took charge of a debate, largely through the physical image of competency she projected and the nonverbal cues of both warmth and authority that she sent. Michele Bachmann’s political leadership credentials may have remained unchanged, but, as Westen writes, “One of the main determinants of electoral success is . . . the feeling voters get when they ‘drive by’ a candidate a few times on television and form an emotional impression.”