Impulsivity is the tendency to act without thinking. For example, you might blurt something out, buy something on a whim, or run across the street without looking. Impulsivity isn’t the same thing as rudeness or lack of self-discipline. It’s a behavior pattern that starts in the brain.

Impulsivity is the tendency to act without thinking about the consequences. For some people, impulsivity is simply a character trait—a preference for spontaneity. For others, it can be a symptom of a significant disorder. Some medications and illegal drugs can also lead to impulsive behaviors.