Personality is used to explain the stability in a person"s behaviour over time or across situations (consistency) The behavioural differences among people reacting to the same situation (distinctiveness) Personality: refers to an individual"s unique constellation of consistent behavioural traits. Personality trait: a durable disposition to behave in a particular way in a variety of situations. Ie, honest, dependable, moody, impulsive, anxious, friendly etc. A small number of fundamental traits determine other, more superficial ones. Ie, a person"s tendency to be impulsive, restless & i r ritable could be derived from the basic tendency to be excitable. If the measurements of a number of personality traits correlate highly with one another, the assumption is that a single factor is influencing all of them. Factor analysis: correlations among many variables are analyzed to identify closely related clusters of variables. created by robert mccrae & paul costa the big 5. Extraversion (positively emotionality): outgoing, sociable, upbeat, friendly, assertive type.