Phrenology is the long-discredited theory that head-shapes and “bumps” in the skull determine your personality and abilities. From the research summarized below, however, it seems that the phrenologists may have been onto something. Skulls may not be a reliable guide to much but brain differentiation may be.

Most past studies of genetic influences on personality have found that the personality traits studied do in fact show substantial genetic heritability. And Even your political attitudes have been shown to have a substantial genetic basis. So the findings below are not inherently surprising. But I think that most of us have assumed that the brain differences involved are more subtle that what is reported below.

As someone with long research involvement in the field of personality measurement, the major reservation I have is that the way personality is “chopped up” in the study below is rather arbitrary. The five factor model is certainly widely used but so is Eysenck’s three factor model and Cattell’s 16 factors.

The broad way that extraversion is described below, for instance, has much in common with the early Eysenck but is rather jarring when looked at in the light of the later finding that two of the components in extraversion — sociability and impulsiveness — are largely independant of one-another. So which of those is influenced by the “bump” in the brain that was found to be correlated with extraversion? As the old saying goes, more research is needed.

Personalities come in all kinds. Now psychological scientists have found that the size of different parts of people’s brains correspond to their personalities; for example, conscientious people tend to have a bigger lateral prefrontal cortex, a region of the brain involved in planning and controlling behavior.

Psychologists have worked out that all personality traits can be divided into five factors, commonly called the Big Five: conscientiousness, extraversion, neuroticism, agreeableness, and openness/intellect. Colin DeYoung at the University of Minnesota and colleagues wanted to know if these personality factors correlated with the size of structures in the brain.

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. The research appears in Psychological Science, a journal of the Association for Psychological Science.

For example, “Everybody, I think, has a common sense of what extraversion is — someone who is talkative, outgoing, brash,” says DeYoung. “They get more pleasure out of things like social interaction, amusement parks, or really just about anything, and they’re also more motivated to seek reward, which is part of why they’re more assertive.” That quest for reward is thought to be a leading factor in extraversion. Earlier studies had found parts of the brain that are active in considering rewards. So DeYoung and his colleagues reasoned that those regions should be bigger in people who are more extraverted. Indeed, they found that one of those regions, the medial orbitofrontal cortex — it’s just above and behind the eyes — was significantly larger in study subjects with a lot of extraversion.

The study found similar associations for conscientiousness, which is associated with planning; neuroticism, a tendency to experience negative emotions that is associated with sensitivity to threat and punishment; and agreeableness, which relates to parts of the brain that allow us to understand each other’s emotions, intentions, and mental states. Only openness/intellect didn’t associate clearly with any of the predicted brain structures.

“This starts to indicate that we can actually find the biological systems that are responsible for these patterns of complex behavior and experience that make people individuals,” says DeYoung. He points out, though, that this doesn’t mean that your personality is fixed from birth; the brain grows and changes as it grows. Experiences change the brain as it develops, and those changes in the brain can change personality.

Source. Journal Reference is: DeYoung et al. “Testing Predictions From Personality Neuroscience: Brain Structure and the Big Five”, Psychol Sci. 2010 Jun;21(6):820-8. Abstract here

Posted by John J. Ray (M.A.; Ph.D.). For a daily critique of Leftist activities, see DISSECTING LEFTISM. To keep up with attacks on free speech see TONGUE-TIED. Also, don’t forget your daily roundup of pro-environment but anti-Greenie news and commentary at GREENIE WATCH . Email me here

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