Trait theory in the context of "Agreeableness"

Human behavior is the potential and expressed capacity (mentally, physically, and socially) of human individuals or groups to respond to internal and external stimuli throughout their life. Behavior is driven by environmental and genetic factors that affect an individual. Behavior is also driven, in part, by thoughts and feelings, which provide insight into individual psyche, revealing such things as attitudes and values. Human behavior is shaped by psychological traits, as personality types vary from person to person, producing different actions and behavior.

Human behavior encompasses a vast array of domains that span the entirety of human experience. Social behavior involves interactions between individuals and groups, while cultural behavior reflects the diverse patterns, values, and practices that vary across societies and historical periods. Moral behavior encompasses ethical decision-making and value-based conduct, contrasted with antisocial behavior that violates social norms and legal standards. Cognitive behavior involves mental processes of learning, memory, and decision-making, interconnected with psychological behavior that includes emotional regulation, mental health, and individual differences in personality and temperament.

Optimism is the attitude or mindset of expecting events to lead to particularly positive, favorable, desirable, and hopeful outcomes. A common idiom used to illustrate optimism versus pessimism is a glass filled with water to the halfway point: an optimist is said to see the glass as half full, while a pessimist sees the glass as half empty. In ordinary English, optimism may be synonymous with idealism—often, unrealistic or foolish optimism in particular.

The term derives from the Latin optimum, meaning "best". To be optimistic, in the typical sense of the word, is to expect the best possible outcome from any given situation. This is usually referred to in psychology as dispositional optimism. It reflects a belief that future conditions will work out for the best. As a trait, it fosters resilience in the face of stress.

In psychology, a mood is an affective state. In contrast to emotions or feelings, moods are less specific, less intense and less likely to be provoked or instantiated by a particular stimulus or event. Moods are typically described as having either a positive or negative valence. In other words, people usually talk about being in a good mood or a bad mood. There are many different factors that influence mood, and these can lead to positive or negative effects on mood.

Mood also differs from temperament or personality traits which are even longer-lasting. Nevertheless, personality traits such as optimism and neuroticism predispose certain types of moods. Long-term disturbances of mood such as clinical depression and bipolar disorder are considered mood disorders. Mood is an internal, subjective state, but it often can be inferred from posture and other behaviors. "We can be sent into a mood by an unexpected event, from the happiness of seeing an old friend to the anger of discovering betrayal by a partner. We may also fall into a mood."

Neuroticism or negativity is a personality trait associated with negative emotions. It is one of the Big Five traits. People high in neuroticism experience negative emotions like fear, anger, shame, envy, or depression more often and more intensely than those who score low on neuroticism. Highly neurotic people have more trouble coping with stressful events, are more likely to insult or lash out at others, and are more likely to interpret ordinary situations (like minor frustrations) as hopelessly difficult. Neuroticism is closely-related to mood disorders such as anxiety and depression.

Individuals who score low in neuroticism tend to be more emotionally stable and less reactive to stress. They tend to be calm, even-tempered, and less likely to feel tense or rattled. Although they are low in negative emotion, they are not necessarily high in positive emotions, which are more commonly associated with extraversion and agreeableness. Neurotic extroverts, for example, would experience high levels of both positive and negative emotional states, a kind of "emotional roller coaster".

A character structure is a system of secondary traits manifested in the specific ways that an individual relates and reacts to others, to various kinds of stimuli, and to the environment. A child whose nurture and/or education cause them to have conflict between legitimate feelings, living in an illogical environment and interacting with adults who do not take the long-term interests of the child to heart will be more likely to form these secondary traits. In this manner the child blocks the unwanted emotional reaction that would have normally occurred. Although this may serve the child well while in that dysfunctional environment, it may also cause the child to react in inappropriate ways, by developing alternate ways in which the energy compulsively surfaces, ways damaging to his or her own interests, when interacting with people in a completely independent environment. Major trauma that occurs later in life, even in adulthood, can sometimes have a profound effect on character. See post-traumatic stress disorder. However, character may also develop in a positive way according to how the individual meets the psychosocial challenges of the life cycle (Erikson).

Extraversion and introversion are a central trait dimension in human personality theory. The terms were introduced into psychology by Carl Jung, though both the popular understanding and current psychological usage are not the same as Jung's original concept. Extraversion (also spelled extroversion) is typically associated with sociability, talkativeness, and high energy, while introversion is linked to introspection, reserve, and a preference for solitary activities. Jung defined introversion as an "attitude-type characterised by orientation in life through subjective psychic contents", and extraversion as "an attitude-type characterised by concentration of interest on the external object".

While often presented as opposite ends of a single continuum, many personality theorists, such as Carl Jung, have suggested that most individuals possesses elements of both traits, with one being more dominant. Virtually all comprehensive models of personality include these concepts in various forms. Examples include the Big Five model, Jung's analytical psychology, Hans Eysenck's three-factor model, Raymond Cattell's 16 personality factors, the Minnesota Multiphasic Personality Inventory, and the Myers–Briggs Type Indicator.