Personality: a particular pattern of behaviour and thinking prevailing across time and situations that differentiates one person from another. Trait theories: hippocrates first explanation of traits, had to do with predominance of the 4 humours in the body. chloric increase of yellow bile tempered and irritable. melancholic increase of black bile gloomy and pessimistic. phlematic increase of phlem sluggish and calm. 3 main factors extroversion(opposite: introversion),neuroticism (opposite: emotional stability), psychoticism (opposite: self control) extroversion: the tendency to seek the company of other people, to be spontaneous and to engage in conversation and other social behaviours with them. Introversion: the tendency to avoid the company of other people to be inhibited and cautious, shyness. neuroticism: the tendency to be anxious, worried and full of guilt. emotional stability: the tendency to be relaxed and at peace with oneself. psychoticism: the tendency to be aggressive, egocentric and antisocial.