Aggression is a behavior aimed at opposing or attacking something or someone. Though often done with the intent to cause harm, it can be channeled into creative and practical outlets for some. It may occur either reactively or without provocation. In humans, aggression can be caused by various triggers. For example, built-up frustration due to blocked goals or perceived disrespect. Human aggression can be classified into direct and indirect aggression; whilst the former is characterized by physical or verbal behavior intended to cause harm to someone, the latter is characterized by behavior intended to harm the social relations of an individual or group.

In psychology, frustration is a common emotional response to opposition, related to anger, annoyance and disappointment. Frustration arises from the perceived resistance to the fulfillment of an individual's will or goal and is likely to increase when a will or goal is denied or blocked. There are two types of frustration: internal and external. Internal frustration may arise from challenges in fulfilling personal goals, desires, instinctual drives and needs, or dealing with perceived deficiencies, such as a lack of confidence or fear of social situations. Conflict, such as when one has competing goals that interfere with one another, can also be an internal source of frustration or annoyance and can create cognitive dissonance. External causes of frustration involve conditions outside an individual's control, such as a physical roadblock, a difficult task, or the perception of wasting time. There are multiple ways individuals cope with frustration such as passive–aggressive behavior, anger, or violence, although frustration may also propel positive processes via enhanced effort and strive. This broad range of potential outcomes makes it difficult to identify the original cause(s) of frustration, as the responses may be indirect. However, a more direct and common response is a propensity towards aggression.