In tough times, people want more in a leader than intelligence, integrity, or the ability to build really tall walls. They want someone who can make a compelling pitch and inspire a sense of urgency—someone with charisma. For decades, scholars have struggled to define this X factor, but they are developing a better idea of how it works.
According to an evolutionary theory proposed by a pair of psychologists, charisma is the ability to convince followers that you can get other members of a wider group to cooperate. These researchers found that exposure to charisma increased generosity: Subjects who saw a ted talk by a charismatic speaker later gave more money to a stranger than did those who saw an uncharismatic one. And thinking about a charismatic person (versus an acquaintance) made people more likely to cooperate with a stranger. 
We’re most swayed by charisma when lacking data on a leader’s record. In one study, subjects had to decide whether to keep or boot a CEO after watching a fake newscast describing him as high or low in charisma and his company’s stock price as rising, sinking, or relatively flat. Charisma helped the CEO most when performance was ambiguous. The researchers also rated past presidential candidates’ charisma, by combing their speeches for charismatic tactics—storytelling, expressing moral conviction, setting high goals. Only when economic indicators were muddled was charisma strongly correlated with votes received. 
To lead, you must rest; fatigue saps charisma. Researchers asked students to give a speech after waking half of them hourly overnight. Viewers gave sleep-deprived speakers lower marks on charisma. They also rated speakers as less charismatic after their own sleep-deprived night. 
A bit of mystery may boost charisma. When a CEO’s success was attributed to intangible factors (“keen insight and vision”) rather than effort (“loyalty and long hours”), he was rated more charismatic. People preferred a hug from a charismatic leader to a hug from a hardworking one; they also preferred his lucky charm, as if his magic might rub off. 
Charisma isn’t magic, though; it’s influenced by mundane factors like height. Among Dutch managers, taller men were seen as more charismatic by subordinates.  And subjects with speedy answers to general-knowledge questions were considered quick-witted, funny, and charismatic by friends. In fact, mental speed was a stronger contributor to charisma than IQ or personality. 
While height and mental quickness elude many of us, charisma can be taught. When researchers trained middle managers and MBA students for 30 to 90 hours in 12 “charismatic leadership tactics,” such as using metaphors and gestures, they found that charisma improved.  Master these tactics, and people may follow you anywhere. Just remember, charisma can be used for good or for, well, building walls. Dazzle responsibly.
 Grabo and van Vugt, “Charismatic Leadership and the Evolution of Cooperation” (Evolution and Human Behavior, forthcoming)
 Jacquart and Antonakis, “When Does Charisma Matter for Top-Level Leaders?” (Academy of Management Journal, Aug. 2015)
 Barnes et al., “Too Tired to Inspire or Be Inspired” (Journal of Applied Psychology, forthcoming)
 Young et al., “Managerial Mystique” (Journal of Management, May 2013)
 Hamstra, “ ‘Big’ Men” (Personality and Individual Differences, Jan. 2014)
 Von Hippel et al., “Quick Thinkers Are Smooth Talkers” (Psychological Science, Jan. 2016)
 Antonakis et al., “Can Charisma Be Taught?” (Academy of Management Learning & Education, Sept. 2011)