A growing body of research on the human brain proves that, for better or worse, leaders’ moods affect the emotions of the people around them. The reason for that lies in what scientists call the open-loop nature of the brain’s limbic system, our emotional center. A closed-loop system is self-regulating, whereas an open-loop system depends on external sources to manage itself. In other words, we rely on connections with other people to determine our moods. The open-loop limbic system was a winning design in evolution because it let people come to one another’s emotional rescue—enabling a mother, for example, to soothe her crying infant.
Scientists describe the open loop as “interpersonal limbic regulation”; one person transmits signals that can alter hormone levels, cardiovascular functions, sleep rhythms, even immune functions, inside the body of another. That’s how couples are able to trigger surges of oxytocin in each other’s brains, creating a pleasant, affectionate feeling. But in all aspects of social life, our physiologies intermingle. Our limbic system’s open-loop design lets other people change our very physiology and hence, our emotions.