Habit, a learned action or other form of behavior that is repeated often enough for it to become a largely automatic response to a particular stimulus or situation. Chains of motor habits or skills are involved in walking, writing, swimming, and the like. Unlike habits, instincts and true reflex actions are not learned but are inherited. Conditioned reflexes, or conditioned responses, however, are acquired, as are habits.

Habits can be acquired by conscious repetition and desire to achieve proficiency in an activity. A person learning to swim observes and imitates the movements of others. At first he concentrates on his breathing and on his arm and leg movements. With experience, however, he learns to make these movements almost automatically.

Many habits are acquired, often without awareness, from influences in the environment. A child, for example, having heard others constantly use meaningless phrases, such as “you know,” may begin to use them himself to such an extent that the use becomes habitual. Some habits develop in response to a person's unconscious needs. Thumb-sucking and nail-biting, for example, are usually attempts to relieve tensions of which the individual is not aware. Such habits ordinarily disappear when the tensions causing them are discovered and eliminated.

Most habits serve a necessary purpose. Simple, routine acts performed habitually leave reasoning and other higher mental processes free to solve complex problems or to provide enjoyment. Habits also play a role in coping with emergencies; an experienced automobile driver, for example, will immediately apply the brakes when a child darts in front of the car.

Alcoholism and addiction to drugs and tobacco are often called habits. The term habit, however, properly refers to responses based on emotional or intellectual rather than organic needs. Addiction to alcohol or drugs is a symptom of personality problems, but the repeated taking of such substances sets up an organic need in the body.