Make sure your body language matches your verbal strategy:
How can we be more successful in persuading others and increase the odds of behavioral compliance? We argue that when a verbal influence strategy is embedded in a nonverbal style that fits its orientation, this boosts the strategy’s effectiveness, whereas a misfit attenuates its impact. In field-experiment 1, agents tried to persuade participants in buying a candybox by using an approach-oriented strategy (Door-In-The-Face, DITF). An eager nonverbal style increased the impact of the DITF, whereas vigilant nonverbal cues rendered it ineffective. Conversely, field-experiment 2 showed that an avoidance-oriented strategy (Disrupt-Then-Reframe) benefited from being presented in a vigilant, rather than an eager nonverbal style, which similarly attenuated its impact. Hence, eager nonverbal cues promote the effectiveness of approach-oriented influence strategies whereas vigilant cues do the opposite and increase the impact of avoidance-oriented influence strategies.
Source: “The Pantomime of Persuasion: Fit Between Nonverbal Communication and Influence Strategies” from Journal of Experimental Social Psychology