In psychology, impulsivity (or impulsiveness) is a tendency to act on a whim, displaying behavior characterized by little or no forethought, reflection, or consideration of the consequences. Impulsive actions are typically "poorly conceived, prematurely expressed, unduly risky, or inappropriate to the situation that often result in undesirable consequences," which imperil long-term goals and strategies for success. Impulsivity can be classified as a multifactorial construct. A functional variety of impulsivity has also been suggested, which involves action without much forethought in appropriate situations that can and does result in desirable consequences. "When such actions have positive outcomes, they tend not to be seen as signs of impulsivity, but as indicators of boldness, quickness, spontaneity, courageousness, or unconventionality" Thus, the construct of impulsivity includes at least two independent components: first, acting without an appropriate amount of deliberation, which may or may not be functional; and second, choosing short-term gains over long-term ones.Impulsivity is both a facet of personality and a major component of various disorders, including FASD, ADHD, substance use disorders, bipolar disorder, antisocial personality disorder, and borderline personality disorder. Abnormal patterns of impulsivity have also been noted instances of acquired brain injury and neurodegenerative diseases. Neurobiological findings suggest that there are specific brain regions involved in impulsive behavior, although different brain networks may contribute to different manifestations of impulsivity, and that genetics may play a role.Many actions contain both impulsive and compulsive features, but impulsivity and compulsivity are functionally distinct.
Theories of impulsivity
Ego (cognitive) depletion
According to the ego (or cognitive) depletion theory of impulsivity, self-control refers to the capacity for altering ones own responses, especially to bring them into line with standards such as ideals, values, morals, and social expectations, and to support the pursuit of long-term goals. Self-control enables a person to restrain or override one response, thereby making a different response possible. A major tenet of the theory is that engaging in acts of self-control draws from a limited "reservoir" of self-control that, when depleted, results in reduced capacity for further self-regulation. Self-control is viewed as analogous to a muscle: Just as a muscle requires strength and energy to exert force over a period of time, acts that have high self-control demands also require strength and energy to perform. Similarly, as muscles become fatigued after a period of sustained exertion and have reduced capacity to exert further force, self-control can also become depleted when demands are made of self-control resources over a period of time. Baumeister and colleagues termed the state of diminished self-control strength ego depletion (or cognitive depletion).The strength model of self-control asserts that:

Just as exercise can make muscles stronger, there are signs that regular exertions of self-control can improve willpower strength. These improvements typically take the form of resistance to depletion, in the sense that performance at self-control tasks deteriorates at a slower rate. Targeted efforts to control behavior in one area, such as spending money or exercise, lead to improvements in unrelated areas, such as studying or household chores.