Hans Eysenck was a psychologist who defined personality as consisting of traits that determine one's adjustment to the environment. His typology included three types: extraversion-introversion, stability-neuroticism, and impulse control-psychoticism. Extraverts are sociable while introverts prefer solitary activities. Neurotics experience disproportionate anxiety. Psychotics exhibit severe psychopathology but also creativity. Eysenck believed personality traits have genetic bases but can be modified through environmental influences and learning. He advocated behavior therapy techniques like systematic desensitization to treat disordered behavior.