Attention-deficit/hyperactivity disorder (ADHD) is a condition that affects an individual's self-control, causing problems with attention span, impulse control, and activity level. ADHD causes difficulty with concentration, persistence, and attention span. Although many individuals with ADHD often find it difficult to concentrate on the task at hand, some experts argue that the term "attention deficit" is somewhat misleading. Instead, they suggest that persons with ADHD actually have difficulty controlling or regulating their attention in general.

For example, they may find it very hard not to pay attention to irrelevant, distracting stimuli in their environment, such as noises or the mere presence of others. At other times, however, they may be so absorbed in what they are doing—especially if it is an activity in which they are very interested—that they do not notice anything else, such as a teacher calling on them. This...