Scientists have found that the size of different parts of people's brains correspond to their personalities

For the study, 116 volunteers answered a questionnaire to describe their personality, then had a brain imaging test that measured the relative size of different parts of the brain. A computer program was used to warp each brain image so that the relative sizes of different structures could be compared. Several links were found between the size of certain brain regions and personality. For example, conscientious people tend to have a bigger lateral prefrontal cortex, a region of the brain involved in planning and controlling behavior. Another one of those regions - the medial orbitofrontal cortex - was significantly larger in study subjects with a lot of extroversion.