Personality traits reflect individual structural differences in the brain, study finds

9 April 2009

It has widely been held that personalities are shaped by a combination of nature and nurture. But a new study published this week has in fact found that major aspects of our personalities are imprinted on our brains as structural differences.

Anatomical bases of personality traits, a collaborative study between the University of Hull, the University of Modena and Reggio Emilia and the University of Parma in Italy and Washington University at St.Louis in the USA, has investigated whether certain characteristics such as novelty seeking, persistence, dependence on reward and avoidance of harm could be correlated with parts of the brain. 

Novelty seeking can be described as impulsive decision making, an extravagant approach to cues of reward and quick loss of temper.

Harm avoidance, on the other hand, manifests as pessimistic worry in anticipation of future problems, passive avoidant behaviour, fear of uncertainty, shyness of strangers and rapid fatigability.

Reward dependence is a trait found in those with an addictive personality; it manifests as sentimentality, social attachment and dependence on the approval of others.

The final characteristic that was examined was persistence. Persistent people tend to be industrious, diligent, hard working, ambitious, overachieving and perfectionist.

The study looked at whether there is a correlation between biological make-up and these traits of personality. These traits were chosen because these are the main dimensions of human personality and can be assessed easily with one of the most reliable measures of personality available, the Three-dimensional Personality Questionnaire (TPQ) devised by Professor Robert Cloninger, a co-author of this study.

The team of researchers asked a large sample of eighty five people to complete the questionnaire and their answers were correlated with their brain scans acquired in three dimensions with a Magnetic Resonance Imaging (MRI) scanner, using a technique that provides a volumetric measure of the brain.

They found that people with high levels of novelty seeking had a more developed inferior part of the frontal lobe, the area above the eye sockets. In contrast, participants with a less developed inferior part of the frontal lobe around the midline inner surface of the brain, had high levels of timidity, approval seeking behaviours and greater tendency to seek gratification from external sources such as food or drugs. 

Additionally, participants who have a very persistent personality trait have more developed parietal lobes and parahippocampus; this region of the brain plays an important role in developing and maintaining memories.

There is some indication that other traits of character such as extroversion and introversion also vary in their expression depending on the difference in function of some brain regions.

Professor Annalena Venneri from the University of Hull explains: "This study shows that personality traits are something you are born with, but their full expression can be modulated during development with the right approach. The fact that traits are reflected in specific anatomical differences is useful to know, however, for instance, when it comes to understanding a child's behaviour and choosing the right approach so that somebody who is, for example, particularly timid might be helped through education and support during development to build their confidence and have the right approach not to be too disadvantaged by their personality. There is no point shouting at a child who is very shy and telling them off because it does not come naturally to them to put themselves forward, but actually knowing there is a biological basis for this helps educators or parents to use the right approach to help a child compensate".

She continues: "People who have a high reward dependent personality but find themselves in an environment where they do not find reward through family support or other types, will seek reward through other means ending up seeking rewards such as food or drugs.  Knowing that someone has such a predisposition could help them adopting preventive strategies and avoid situations where they might seek rewards which could be potentially harmful"