It is a common experience: You’re deep in conversation with someone and suddenly realize you’re both holding the same pose, leaning forward and propping an elbow on the table. Or you notice you’re suddenly starting to pick up the other person’s Southern accent or fast, loud speech.

Mirroring a conversation partner’s gestures, expressions, posture, vocal pitch or tone can reflect rapport or a desire to please, research shows. It is seen most often between romantic partners, but it happens at work, too, in networking sessions, meetings and conversations with colleagues.

Creepy, maybe. Most people do it unconsciously. But mirroring can help you create powerful connections with others. This behavior, often called “the chameleon effect,” often causes others to like and trust you more. Professional networkers, negotiators and salespeople say they use mirroring to help them engage more deeply in a conversation and understand the person they’re talking with.

Retail salespeople who were told to mimic the nonverbal and verbal behavior of customers sold more products and left customers with a more positive opinion of the store, according to a 2011 study of 129 customers by French researchers. In another study, published in 2008 in the Journal of Experimental Social Psychology, 62 students were assigned to negotiate with other students. Those who mirrored others’ posture and speech reached a settlement 67% of the time, while those who didn’t reached a settlement 12.5% of the time.

People who are deeply engaged in conversation are often surprised to realize they’re mirroring each other. Diane Darling was on a video call recently with a friend in France when she noticed both were leaning back with their arms extended overhead “as if we were doing a morning stretch—but for her it was 2 o’clock in the afternoon,” says Ms. Darling, a Boston networking consultant. “Oh my gosh, we’re in the same position,” she told her friend.

Executive coach Nancy Capistran sometimes mirrors the posture or gestures of clients during problem-solving discussions, but client John Dudley says she does it so naturally he doesn’t notice. Photo: Patrick Rogers

This relaxed, open posture reflects trust, and their simultaneous gesture sprang from a moment of deep connection, says Ms. Darling, author of “The Networking Survival Guide.”

Researchers using brain-imaging technology in new ways have recently discovered that these shared behaviors go beyond simple mimicry. Scientists using functional MRIs to study listeners and speakers have found that they are “dynamically coupled,” with speakers’ and listeners’ brains reacting and adapting to signals from each other, says a 2016 study co-written by Uri Hasson, an associate professor of psychology and neuroscience at Princeton University. Dr. Hasson likens the connection to a kind of wireless bonding of brains. The brain’s mirroring capacity is the basis for this interplay of signals and reactions, and nonverbal cues enhance it.​

This kind of alignment fosters closeness and trust. “The extent to which people are able to create this brain-to-brain coupling makes them more powerful,” says Noah Zandan, chief executive and co-founder of Quantified Communications, an Austin, Texas, communications analytics company. “It’s useful in any environment where collaboration is going to be more helpful than hostility.”

Deliberately trying to mirror another person’s behavior without being truly engaged can backfire, however. Others are likely to notice and see it as an attempt at manipulation. “We tend to like people who imitate us—as long as we don’t notice that they’re doing it,” says Chris Frith, an emeritus professor of neuropsychology at University College London and co-author with Dr. Hasson of the 2016 study.

A job candidate might copy an interviewer’s posture and speaking style in an attempt to make a good impression, for example. Sometimes this is obvious to the interviewer, and sometimes it isn’t, depending on the job candidate’s skill and subtlety, research shows.

Dos and Don’ts Mirroring typically works best when it is unconscious. Doing it consciously requires some subtle skills: DO: Build a connection first. Make listening and understanding the other person your priority.

Start by nodding and tilting your head as you listen.

Try matching the other person’s vocal tone and pace.

If that works, move on to mirroring gestures and posture.Don’t try to fake it by pretending to be interested when you’re not. You’ll almost certainly be found out, damaging the relationship. DON’T: Try to fake it by pretending to be interested when you’re not. You’ll almost certainly be found out.

Mirror negative nonverbal signals, such as crossing arms in front of your body or stepping back.

Try to copy the person’s gestures, movements and expressions exactly.

Devote so much energy to mirroring that you feel stressed.

It is wiser to begin to feel a sense of connection with an interviewer before trying to mirror his behavior. You should already be showing genuine openness and interest via nonverbal cues, facing the interviewer squarely and making frequent eye contact. Also, stick to behaviors that come naturally.

“If you purposely try to copy everything someone does, it’s going to be awkward, says Ellen Keiley, a business-development coach in Arlington, Mass.

Skilled salespeople, negotiators and coaches say mirroring listeners’ behavior can be a helpful tool for immersing oneself quickly and deeply in conversation. Executive coach Nancy Capistran often mirrors clients’ gestures and posture during coaching sessions as an expression of her involvement and interest, she says. “I meet them where they are. It’s automatic for me,” says Ms. Capistran, founder of an Ashland, Mass., leadership-consulting firm. “It really helps build rapport.”

When a senior executive she was coaching recently began talking about a tough problem he was wrestling with, he leaned forward and put his elbow on the desk. She did the same thing without planning it, she says. Her nonverbal cues “let him know that I was in the trenches with him and we could figure it out together,” she says. The executive relaxed and began talking openly, Ms. Capistran says. “You can get to the core of issues so much more quickly” when you understand the power of body language, she says.

Her client, John Dudley, says Ms. Capistran mirrors his behavior so naturally during their conversations that he wasn’t aware of it until she mentioned it recently, suggesting “she’s doing it well,” says Mr. Dudley, president and chief executive of United Home Experts and United Building Systems, Ashland, Mass., home-improvement contractors. He reads her nonverbal cues as a sign of engagement and interest.

Mr. Dudley trains his own salespeople to match the pace of prospective clients’ conversations, urging those who speak slowly to speed up when talking with prospects who are in a rush, for example. Otherwise, he tells his salespeople, “you’re going to drive them nuts.”

Sales trainer David Hoffeld says mirroring another person’s body language helps him focus on the person’s needs and understand his viewpoint. “It’s not something you do to someone. It’s something you do with someone,” says Mr. Hoffeld, author of “The Science of Selling.” He adds, “The very process of mirroring will help you keep your focus where it should be—on the other person.”

When he began a pitch to a chief executive officer who was relaxed and leaning back in his chair, Mr. Hoffeld sat back too, mirroring the executive’s posture, gestures and choice of words, says Mr. Hoffeld, chief executive officer of a Minneapolis sales-training firm. As the CEO became more interested in the training program Mr. Hoffeld was selling, he leaned forward and began gesturing with both hands. Mr. Hoffeld did the same, “and we were off to the races,” says Mr. Hoffeld. He soon made the sale.

Write to Sue Shellenbarger at sue.shellenbarger@wsj.com