Anger is an emotional state that may range from minor irritation to intense rage. The physical effects of anger include increased heart rate, blood pressure, and levels of adrenaline and noradrenaline. Some view anger as part of the fight or flight brain response to the perceived threat of pain. Anger becomes the predominant feeling behaviorally, cognitively and physiologically when a person makes the conscious choice to take action to immediately stop the threatening behavior of another outside force.
The external expression of anger can be found in facial expressions, body language, physiological responses, and at times in public acts of aggression. Animals and humans for example make loud sounds, attempt to look physically larger, bare their teeth, and stare. Anger is a behavioral pattern designed to warn aggressors to stop their threatening behavior. Rarely does a physical altercation occur without the prior expression of anger by at least one of the participants. While most of those who experience anger explain its arousal as a result of "what has happened to them," psychologists point out that an angry person can be very well mistaken because anger causes a loss in self-monitoring capacity and objective observability.
In the world of humans, the unique use of codified symbols and sounds -written and spoken language, pain or the threat of pain can be perceived from written and verbal sources. Humans may not perceive an immediate physical threat, but pain can be felt psychologically. Due to humans' capacity to imagine the distant future, the threat of pain can also arise purely from the imagination, and not be based on anything happening in the immediate present. In humans, anger often arises when another human being is perceived to violate expected behavioral norms related to social survival. These violations break social or interpersonal boundaries, or may be ethical or legal violations.

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