When people are in a certain mood, whether elation or depression, that mood is often communicated to others. When we are talking to someone who is depressed it may make us feel depressed, whereas if we talk to someone who is feeling self-confident and buoyant we are likely to feel good about ourselves. This phenomenon, known as emotional contagion, is identified here, and compelling evidence for its affect is offered from a variety of disciplines - social and developmental psychology, history, cross-cultural psychology, experimental psychology, and psychopathology.