 8. The Neurobiology of Personality  197
Both behavioral and neural research have 
provided evidence that the core psychologi -
cal function underlying extraversion is sen -
sitivity to reward (De  Young, 2015; Smillie, 
2013; Wacker & Smillie, 2015). People high 
in extraversion are highly sociable because 
they find social interactions more rewarding 
than do people low in extraversion; they are 
assertive and driven because they are more 
motivated to pursue rewards; and they expe -
rience more positive emotions because they 
find more experiences rewarding.
The brain’s reward or valuation network 
comprises the regions of the midbrain (just above the brainstem) that contain the cell 
bodies of dopaminergic neurons (known 
as the substantia nigra and the ventral teg -
mental area) and also the various regions to 
which those dopaminergic neurons project 
axons that release dopamine. The latter re -
gions include subcortical nuclei (nucleus ac -
cumbens and caudate nucleus), the anterior 
cingulate cortex (ACC), and the medial or -
bitofrontal cortex (OFC; sometimes labeled 
ventromedial prefrontal cortex). Although 
not often considered in relation to reward, 
the amygdala is also important for this net -
work, because it is involved in processing TABLE 8.1.  Likely Neural Correlates of the Big Five and Their 10 Aspects
Neurotransmitters 
and hormones Brain structures and regionsLarge-scale brain 
networks
Extraversion Dopamine 
(value  system)Substantia nigra and ventral 
tegmental area
Nucleus accumbens
Medial orbitofrontal cortex
AmygdalaReward or valuation 
network
Assertiveness — — —
Enthusiasm Endogenous opiates — —
Neuroticism Serotonin
CortisolAmygdala
Hypothalamus
Insula
Medial prefrontal cortex and 
anterior
cingulate cortex
Dorsolateral prefrontal cortexFight–flight–freeze 
system
Hypothalamic–
pituitary–adrenal axis
Withdrawal — Hippocampus Behavioral inhibition 
system
Volatility — — —
Openness/intellect Dopamine 
(salience  system)Substantia nigra and ventral 
tegmental areaDefault network
Intellect — Dorsolateral prefrontal cortex Frontoparietal control 
network
Openness to experience — Reduced coherence in frontal 
white matter—
Conscientiousness Serotonin Dorsolateral prefrontal cortex
Insula
Lateral orbitofrontal cortexVentral attention 
network
Salience network
Industriousness — — —
Orderliness — — —
Agreeableness — — —
Compassion — Insula Default network
Politeness Serotonin
Testosterone— —
Note . This list is not intended to be exhaustive.