Hans and sybil eysenck described personality differences by identifying

In the field of personality psychology there are two currents, one that states that the personality consists of three dimensions or superfactors, of which Eysenck was its greatest defender, and another, currently more accepted, which argues that there are five. The three dimensions postulated by Eysenck's PEN model are Extraversion, Neuroticism and Psychoticism. Each of them is related to what Eysenck considered to be the motors of behavior that are reproduction, conservation and self-defense, respectively. He also added a fourth factor, Intelligence, although he never linked it to his PEN theory. Each of these dimensions had a biological basis at the neurochemical level and was composed of nine factors or traits.