Some people are 'people' people - warm, outgoing and emotional - while others are more reserved and aloof. Scientists at Cambridge University and Oulu University in Finland investigated these personality differences and how they were related to differences in brain structure. 41 participants filled in a personality questionnaire which asked them how well they thought they connected to other people, how they showed their emotions and whether they liked to please people. The scientists then used brain scans to analyze the concentrations of grey matter in different parts of the participants' brains. People who scored highly for warmth and extroversion on the questionnaires had more grey matter in their orbitofrontal cortex (just above the eyes) and in a structure deep within the brain called the ventrial striatum, areas which have already been linked to the enjoyment of sweet tastes and sex.