Genetics and Epigenetics
• An individual may inherit a genetic predisposition for high stress reactivity, which can be modified by early-life nurturing or trauma.
• Epigenetic changes—like DNA methylation due to prolonged stress—can influence vulnerability to depression.

Neurobiology
• A hyperactive amygdala might cause a heightened response to perceived threats, influencing a person’s tendency toward anxiety.
• Damage to the frontal cortex can impair decision-making and impulse control, dramatically altering behavior.

Endocrinology
• Elevated cortisol levels during chronic stress can affect learning and memory, shaping responses to future challenges.
• Testosterone fluctuations can influence aggression and risk-taking behaviors in competitive contexts.

Developmental and Life History Factors
• Early childhood experiences, such as secure attachment or neglect, can determine emotional regulation later in life.
• Critical periods in brain development can set long-lasting behavioral patterns; for example, language acquisition or social skills.

Social and Cultural Context
• Cultural norms dictate acceptable behavior, such as the expectation of independence in some societies versus community reliance in others.
• Peer influence during adolescence can shape risk-taking behaviors and social identity.

Evolutionary Background
• The fight-or-flight response is rooted in survival strategies animals evolved to escape predators.
• Social hierarchies observed in primates reflect evolutionary pressures that also influence human competition and cooperation.