- Robert McCrae and Paul Costa developed the "Big Five" model of personality which identifies the five main personality traits as neuroticism, extraversion, agreeableness, openness to experience, and conscientiousness.
- Personality theories can be categorized into four main perspectives: psychodynamic, behavioral, humanistic, and biological. Sigmund Freud's psychodynamic theory focuses on unconscious drives and childhood experiences.
- Behavioral theories like Skinner's operant conditioning look at environmental influences on personality. The humanistic perspective emphasizes free will and self-actualization as proposed by theorists like Carl Rogers and Abraham Maslow.