in psychology, any regularly repeated behaviour that requires little or no thought and is learned rather than innate. A habit—which can be part of any activity, ranging from eating and sleeping to thinking and reacting—is developed through reinforcement and repetition. Reinforcement encourages the repetition of a behaviour, or response, each time the stimulus that provoked the behaviour recurs. The behaviour becomes more automatic with each repetition. Some habits, however, may form on the basis of a single experience, particularly when emotions are involved. Habits, as discussed by William James in his Principles of Psychology, are useful as the means for conserving higher mental processes for more demanding tasks, but they promote behavioral inflexibility.

Five methods are commonly used to break unwanted habits: the replacement of the old response with a new response—e.g., eating fruit instead of candy to satisfy a craving for sweetness; the repetition of the behaviour until fatigue or another unpleasant response takes over—e.g., being forced to smoke cigarettes until nauseated so that a repulsion for cigarettes replaces the desire to smoke; the change of environment to separate the individual from the stimulus that is prompting the response; the gradual introduction of the stimulus that is provoking the behaviour—e.g., overcoming a child's fear of adult dogs by giving him a puppy; and punishment, which is probably the least effective method.