Tuesday, June 22, 2010

This is your brain on...you?

Could it be that the 19th century phrenologists, who purported to derive personality traits from the shape of the skull, were not wrong, just early? Scienceblog summarizes a study by Dr. Colin DeYoung published in Psychological Science
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. 

C'mon, this is a joke, right? Below, a quick rundown of the nineteenth century pseudoscience of phrenology from Wikipedia:
Phrenologists believed that the mind has a set of different mental faculties, with each particular faculty represented in a different area of the brain. These areas were said to be proportional to a person's propensities, and the importance of the given mental faculty. It was believed that the cranial bone conformed in order to accommodate the different sizes of these particular areas of the brain in different individuals, so that a person's capacity for a given personality trait could be determined simply by measuring the area of the skull that overlies the corresponding area of the brain.
Phrenology was a handy tool for racists. Favored personality traits corresponded remarkably with Caucasian high foreheads and other admired features. Certain physical types were held to be predisposed toward criminal behavior.  I remember the narrative avatars of Charlotte Bronte, that sage high-foreheaded bigot, sizing up lovers and villains for organs of veneration, bumps of benevolence, intellect, etc.

I'm in no position to judge Dr. De Young's research.  But I am very suspicious of claims to find a simple correspondence between physical features of the brain and personality type, as I am of research that purports to link various emotional experiences to specific brain activity. 

For the record, that "big five" sounds pretty dicey, too.


1 comment:

  1. I think your instincts are correct. You should check out some of Mark Liberman's posts at Language Log on the (poor) state of contemporary science journalism. Something like "conscientious people tend to have a bigger lateral prefrontal cortex" probably would be better phrased in terms of the real world as "based on this study, if you meet someone who has a larger-than-average prefrontal cortex, there's a slightly greater than 50% chance that they're in the upper half of the population in terms of conscientiousness". As always, it's hard as a member of the GP to be sure since we can't access the study.