Next time you watch a TED talk or a political speech, take a moment to look closely at the speaker’s hand movements. Is the motion slow or energetic? Is it subtle or expansive? And how are the hands mostly moving – vertically or horizontally?

It is well known that non-verbal cues can have more of an influence on the way that a message is received than the actual words spoken. As BBC Capital recently explored, a deeper voice increases perceptions of authority, for instance – and this even appears to influence a CEO’s earnings and how long they stay with a company.

Your hand gestures can even change people’s perceptions of your physical height – making you appear a few inches taller or shorter

Now a series of recent studies from Markus Koppensteiner at the University of Vienna has examined the way that people talk with their hands – with remarkable results. Even when all other factors have been taken into account, your hand gestures signal important elements of your personality like extraversion and dominance. They can even change people’s perceptions of your physical height – making you appear a few inches taller or shorter.

Koppensteiner’s findings would seem to recall the famous research on “power poses” – the strategy, for instance, of standing, like Superwoman, with your hands on your hips and your feet planted wide apart. These small gestures of confidence are thought to feedback into the brain, leading people to feel more assertive before public speaking.

In the words of the Harvard University professor, Amy Cuddy, who conducted many of these studies, “you fake it until you make it”.

Cuddy’s research had come under criticism, with some serious doubts over the reliability of the finding, but recent research shows that power poses do have a robust effect on people’s self-perceptions.

There are some important differences with the new research, however. Power poses are primarily designed to be performed in private to increase confidence before a meeting – and they are largely static positions rather than fluid movements.

Koppensteiner’s research, in contrast, examines the motion of the speakers’ hands as they talk and the ways that this influences others’ perceptions. In a typical study, he would take real videos of politicians’ speeches, and then transformed them into animated stick figures so that confounding factors – like their facial expressions – would no longer be visible. You can see one example in the video below:

Participants were then asked to rate the silent, animated movies for specific personality traits.

Although some traits, such as conscientiousness, appeared to be hard to discern from the hand gestures, others were clearly visible. Extraversion, for instance, appeared to be linked more to hand movements overall, punctuated with only brief periods of stillness.

Extraversion appeared to be linked more hand movements overall, punctuated with only brief periods of stillness

Perceptions of authority, meanwhile, appeared to come from the scale of vertical movements – whether your hand sweeps from the level of the lectern, say, to shoulder height. People who regularly make these kinds of expansive gestures tend to be rated as being less agreeable, but more dominant. “It is a very consistent result, across many papers of mine,” Koppensteiner says.

In one particularly striking article from 2015, Koppensteiner found that these personality ratings, based solely on the silent animations of stick men, could predict the amount of applause the politicians actually received in the real-life speeches that the animations had been drawn from.

There was a catch, however, since those rating also predicted whether the politicians were heckled – suggesting that the gestures of dominance can be perceived as positive or negative depending on the context. Perhaps, in the wrong circumstances, gestures of dominance can also be seen as arrogant, aggressive, or overbearing.

Tall stories

Besides altering the perceptions dominance, the expansive vertical hand movements also altered estimates of the speaker’s physical height. “People were mostly impressed by the real height of the stick figures, but if they moved their arms up and down vigorously, and with lots of expansive arm movements, you seem to be judged as being taller,” he says.

The exact psychological mechanism is not clear. Since previous research had shown that taller people are naturally considered to be better leaders, it’s possible that the movements create a kind of visual illusion to increase your perceived height, and this then contributes to perceptions of greater dominance. But it could also work in the opposite direction: the increased dominance leads to the altered perceptions of height.

“We know that if people are in high-status positions, they are seen as being taller,” Koppensteiner says. As he points out, people often overestimate Tom Cruise’s height, and although that could be due to clever camera work, it could also come from the way he projects his confidence.

The most successful TED talk videos contain almost twice as many hand gestures

Koppensteiner’s results would seem to support the conclusions of less formal studies. The author and body language trainer Vanessa Van Edwards, for instance, has analysed hundreds of TED talks to understand why some talks go viral while others sink with very little interest – even when they deal with broadly similar topics conveying equally enticing messages. She found that the most successful videos contained almost twice as many hand gestures (465 compared to 272). And in line with Koppensteiner’s research, the number of expansive gestures also predicted viewers’ ratings of the speakers’ charisma and competence.

It’s worth emphasising that Koppensteiner hasn’t yet tested whether people can mimic these expansive gestures to change the ways they are perceived.  Even so, he suspects that many people are putting on something of a deliberate performance, although that may be easier for some personality types than others. “You can produce certain behaviours and certain outcomes and impressions in people, but there may limits,” he says.

Given that public speaking is consistently rated our biggest phobia, any small tip to improve the experience could offer a small confidence boost that will surely be welcomed by many people. Let your hands do the talking, and you might just find that the words take care of themselves.

David Robson is a science writer based in London. He is @d_a_robson on Twitter.

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