Cross-cultural personality change throughout the lifespan: a result of brain development?
Generally, the authors found an increased level of neuroticism in the 18-21 year old range, a sensitive time wrought with angst and rebellion. This makes sense because frontal lobes, responsible for executive functioning and emotional control, are still in development (NIMH). Neurotics tend to respond poorly to environmental stress, interpret ordinary situations as threatening, and are more impulsive. These personality characteristics map well to frontal lobes that have not been fully developed.
The Big Five Personality Traits
The authors also found that adults 50+ years old evidenced lower extraversion and openness and higher agreeableness and conscientiousness. Studies have shown that extraverts demonstrate increased sensitivity to reward signals and novelty seeking, suggesting that the dopaminergic system is involved (Cohen et al., 2005; Golimbet et. al, 2007). One study found that striatal D2 receptor availability predicted socially desirable responding (Reeves et al., 2007). Additionally, age-related decline in dopamine D2 receptors is evident (Volkow et al, 1996, 2000). Taken together these studies may offer up one piece of the explanatory puzzle as to why extraversion declines in older adults.
Openness to experience has been suggested to map well with the orbitofrontal cortex, an area known for decision-making, reward processing and emotional processing (Sutin et al., 2009 ). An absence of the posterior orbital sulcus (a part of the orbitofrontal cortex) in healthy subjects has been positively associated with openness to experience (Roppongi et al., 2010). Interestingly, older adults evidence tissue loss in the orbitofrontal cortex, perhaps explaining the decrease in openness to experience found later in life (Resnick, Lamar, & Driscoll, 2007).
In terms of agreeablness, one study found that smaller right orbitofrontal lobe volume was associated with low agreeableness while smaller left orbitofrontal volume was correlated with high agreeableness in patients with frontaltemporal dementia (Rankin et al., 2004). Perhaps in normal aging the left orbitofrontal cortex, in particular, gradually loses tissue over time.
Regarding conscientiousness, Jackson, Belota, and Head (2009) discovered that those who were rated as higher on this personality trait showed larger regional volumes in prefrontal and mediotemporal regions and less decline with advanced aging.
The influence of brain development on cross-cultural personality changes in the context of aging, particularly the orbitofrontal cortex, is well worth considering. However, one should not forget about all the other important pieces of the puzzle (i.e. maturational, cultural, cohort and sampling effects). Needless to say, further research needs to be done in order to shed light on this intriguing link between personality and the aging brain.
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