Through the handshake we establish the level of trust between ourselves and the other individual. We divine earnestness, truthfulness, and we measure the depth of friendship or deceit in the other party.
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What's with politicians and all that handshaking? Every campaign appearance starts and ends with concentrated handshaking sessions with as many potential voters as possible despite the danger candidates face when wading into a crowd of strangers peppered with adversaries. Some campaign appearances are completely focused around pressing the flesh -- a fleeting gripping of palms accompanied by little or no verbal exchange of substance, but to politicians that brief handshake is priceless; worth even risking death. That's because handshaking and body language in general communicate powerfully and deeply about the internal state and intentions of other people. Through the handshake we establish the level of trust between ourselves and the other individual. We divine earnestness, truthfulness, and we measure the depth of friendship or deceit in the other party. In all formal social interactions and in business, the handshake in western society precedes discussion and seals the deal at the end.

Body language can communicate and persuade more powerfully even than what is said. After two presidential debates in which the candidates crammed endless facts and rehearsed to hone their arguments, what everyone remembers and is talking about afterwards is the body language of the candidates -- Obama's grimace, Biden's smirk, Ryan's composure under fire.

These debates always start and end with handshakes between contestants and often with the moderator. According to a new study published in the Journal of Cognitive Neuroscience, scientific evidence supports what all politicians know -- the handshake touches neural circuits inside the brain that predispose a person toward positive feelings of competence, trustworthiness, and it opens a relationship of positive cooperation while suppressing negative feelings and avoidance behavior.

The research team led by Sandra Dolcos of the University of Illinois, showed subjects brief video clips of two people meeting in a business interaction. In some of the clips the encounter began with a handshake. In the others, the two people did not meet by shaking hands. The clips ended with the parties either joining in collaboration or separating and displaying avoidance body-language, such as crossing arms to discourage further interaction. The subjects then rated each encounter they observed on a 6-point scale judging the host's competence, trustworthiness, and interest in doing business. The data showed much higher ratings of all three measures (competence, interest in doing business, and trustworthiness) if the encounter was preceded by a handshake. The power of a handshake in boosting trust and partnership was evident regardless of whether the encounter ended positively or negatively (that is, whether the scene ended by the two approaching and doing business or avoiding further interactions).

The subjects underwent these tests while inside a functional MRI machine, so the scientists could peer inside the brains of the observers and see what effect the handshake might have on their mental processing. They saw that a part of the brain called the nucleus accumbens activated when the encounter was preceded by a handshake. The amygdala brain region activated when the greeting ended positively in doing business. The observer's skin conductance was also monitored to measure stress. Just as in a lie detector, skin conductance measures the unconscious reflex that makes our palms sweat when we are nervous. Increased activity of the amygdala was associated with markedly reduced stress.

The nucleus accumbens is a central component of the reward pathways that are linked to positive experiences and emotions such as excitement. The researchers conclude that a handshake preceding social interactions positively influenced the way individuals evaluate a social interaction. The handshake reduced avoidance behaviors, suppressed negative impressions, and boosted the interest in further interactions. These outcomes were evident in the scored evaluations of the encounter and also seen in the working brain circuits underlying positive social interactions and emotions.

Social interactions and getting to know people require ascertaining the other person's internal state of mind and character. Touch, non-verbal communication via body language, even as formalized touching in western society through the handshake, allows our mind to tap into the other person's mind. This communication through touch and body language conveys vital information through a rich unconscious and universal language that transcends spoken language.

As a teenager in 1968 I shook Robert Kennedy's hand in a crowd at a political rally two weeks before his death. His palm was warm, dry, and comforting. That one-on-one physical connection through our linked hands conveyed an instantaneous silent exchange of information that had a powerful persuasive impression on me. Forty-four years later I still remember that handshake vividly. I remember nothing at all of what was said in his speech that followed. Politics aside, I felt I knew with certainty something deep and true about the internal character of the man. A truly extraordinary individual, who believed in what he said and would work with all his strength, give everything he had, to achieve his vision.

S. Dolcos, K. Sung, J.J. Argo, S. Floro-Henry, and F. Dolcos (2012) The power of a handshake: Neural correlates of evaluative judgments in observed social interactions. J. Cognitive Neuroscience, on-line advanced publication.

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