Use mimicking effectively based on your partner and the situation.
Newbies and veterans to improv agree that the scariest part is simply starting a scene. To overcome this fear of the unknown, the best advice I've heard is to mimic your partner, from physical quirks, to energy level, to object-work. If he slouches, speaks like a Frenchman and slowly smokes a cigarette, slink over and light up alongside him. Mimicking not only gives you something to do but also feels reassuring, as if you both know where the scene is heading.
But sometimes "anti-mimicking" can be rewarding. This happens all the time with the Improvised Shakespeare Company at the iO: One improviser plays a pompous king and the others immediately assume subservient postures and energies, or one plays an evil courtesan and another quickly becomes her stupid sister.
To mimic or not to mimic? That is the question, and not just on stage but in real-life. Mimicry is a tricky tool; sometimes you should do as the Romans do and other times the opposite. How to tell? Psychology provides some clues.
Mimicking for confidence: Social psychologist and HBS Professor Amy Cuddy suggests that by mimicking the nonverbal displays of powerful people – leaning forward, spreading your hands apart on a table, and generally taking up space – you can trick yourself into feeling more confident. In a 2010 paper, Cuddy and her colleagues explain that by mimicking this physicality for only a few minutes, people can actually raise their testosterone and lower their cortisol levels, creating feelings of power and risk-tolerance. (Watch her Ted Talk for details.) If you're nervous before the first day at your internship or job, try this out!
Mimicking for comfort: Ok, so mimicking can rev us up for our jobs...but how about when we arrive and try to fit in? At least for the first few months, we may want to use that dominant posture sparingly. In a 2003 paper, Professors of Organizational Behavior Larissa Tiedens and Alison Fragale suggest that people experience increased comfort and liking when in complementary postures; if one person assumes a dominant, expansive posture (e.g., sitting with legs apart, arm over an adjacent chair), the other often assumes a submissive, constricted posture (e.g., sitting with legs together, hands in lap). Further, in hierarchical environments, people may actually feel more comfortable when status is signaled via an appropriate dominant/submissive posture. If you want to keep your job, "anti-mimicking" your boss may be the way to go.
Mimicking for closeness: How about your love life? Several studies propose that mimicking helps people process the emotional expressions of others; for example, you'll better appreciate your friend's delight about her job offer if you yourself adopt a happy face. In this vein, a 1987 study by social psychologist Robert Zajonc and his team suggests that facial mimicry is linked to empathy. They compared the faces of couples before marriage and after 25 or more years of marriage (controlling for age) and found greater facial similarity for those married longer and with reportedly higher-quality marriages. Quite plausibly, couples who more frequently mimicked each other's facial expressions better empathized emotionally and, over time, experienced similar facial changes (from exercising similar muscles). If you watch your significant other's facial expressions when you're emotional, you may have a litmus test for whether they're Mr. or Mrs. Right.
To mimic or not to mimic? In a Shakespearian sort of way, it may be a matter of power, propriety, and love.