Personality Neuroscience: Unlocking The Mystery of The Brain in Order to Understand The Whole Person

Posted by psychometricsforumblog on April 25, 2013

This month, President Obama unveiled plans to fund a $100 million project to discover how different regions of the brain connect and result in the many complex functions that we as human beings are capable of. The BRAIN initiative, similar in its audacious attempt to push the boundaries of human knowledge as the Human Genome project, will endeavour to discover more about the most complex structure in the universe.

So, I was inspired to reconnect with my neuroscience roots myself and through a recommendation of our very own Psyche Editor; Mr Starkey, came across the intriguing field of ‘Personality Neuroscience’. The aim of this field, is “to understand both the biological systems that are responsible for the states associated with [personality] traits and the parameters of those systems that cause them to function differently in different individuals” (DeYoung, 2010).  A leading figure within Personality Neuroscience is Dr Colin DeYoung, who The Psychometrics Forum hosted via teleconference from the USA in 2011.

From my reading of this complex, interdisciplinary field, it seems that a personality trait (Big 5, for example) is mapped onto a certain brain region, using the psychological function of each trait as a stepping stone for this process. In other words, a trait such as Extraversion is hypothesised to have a psychological function i.e. approach towards potential rewards, which is associated with particular brain regions and neurotransmitters such as dopamine. Therefore, the psychological function provides the link between a biological personality trait and its home within the brain. But why is this important? Simply put, there is a two-way street between personality and neuroscience. Having an understanding of the biological basis of personality traits can help us to refine personality theory, while personality theory can help us to begin understanding the neurological basis of human behaviour (DeYoung, 2010).

As well as taking the position that the Big five factors of personality collapse upward into two broader factors (McCrae et al., 2008), DeYoung suggests that there are mid-level factors between the Big Five and their facets (DeYoung, Quilty, & Peterson, 2007). The figure below demonstrates the neurobiological taxonomy of personality traits. DeYoung (2010) uses this taxonomy of personality to shape his theorising regarding the psychological function and therefore the brain region responsible for such traits. In an attempt to simplify this rather messy and far from clear-cut body of research, in the table below, I have outlined some of the key regions associated with each of the big five personality traits. Please forgive the rather crude approach here, as it does seem that we are in the infancy stage of this approach, nevertheless I’m sure my old Neuroscience tutor would not be impressed(!)

Figure 1 – The Taxonomy of the Big Five Personality traits

Table 1 – Table showing Each Big Five trait with its corresponding Psychological Function and associated brain region.

Trait	Psychological Function	Brain region/neurotransmitter*	Also associated with	Diagram
Stability (Low Neuroticism, Agreeableness and Conscientiousness)	General tendency to regulate or restrain potentially disruptive emotion and behaviour.	Serotonin – has regulatory or inhibiting effects on mood, behaviour & cognition.	Low levels of serotonin are associated with aggression, poor impulse control and depression. Whereas serotonin boosting drugs mitigate these problems.	-
Plasticity (Extraversion & Openness)	General tendency to explore and engage with possibilities.	Dopamine – the dopaminergic system has two branches. One branch influences brain structures such as the Nucleus Accumbens and Amygdala, which are involved in motivation, emotion and reward i.e. Extraversion. While the other branch influences the Pre-frontal Cortex, which is responsible for higher cognition (Openness).	The Nucleus Accumbens – the pleasure centre, thought to be associated with reward, pleasure, laughter, addiction, aggression and fear. The Amygdala – forms part of the limbic system and is thought to be associated with memory and emotional reactions.	Amygdala
Extraversion	Sensitivity and approach to reward and positive affect. In other words, the drive for reward, rather than enjoyment of it once it is received.	Medial Orbitofrontal Cortex, Nucleus Accumbuns, Amygdala, Striatum.	The Medial Orbitofrontal Cortex is associated with coding the value of rewards.	The Orbitofrontal Cortex
Neuroticism	Sensitivity to punishment and negative affect i.e. anxiety, depression, anger, irritation, self-consciousness, rumination, and vulnerability.	Amygdala and Anterior Cingulate. Medial Pre-frontal Cortex activity which is suggestive of poor emotion regulation. Right frontal lobe (withdrawal aspect of Neuroticism).	The Anterior Cingulate is linked to a wide variety of autonomic functions, such as regulating blood pressure and heart rate, as well as rational cognitive functions, such as reward anticipation, decision-making, empathy, impulse control, and emotion.	The Anterior Cingulate is located towards the frontal lobe in the highlighted Cingulate Cortex.
Agreeableness	Tendency toward altruism as opposed to exploitation of others.	Superior Temporal Sulcus, Posterior Cingulate Cortex, and Fusiform Gyrus. These areas are involved in social information processing.Left Dorsolateral Prefrontal Cortex – associated with emotional regulation.	Agreeableness predicts tests of empathy, theory of mind and other forms of social information and emotional processing, hence these regions have been implicated.	The Superior Temporal Sulcus is located in the bottom fold of the Gyrus (highlighted in green below).The Posterior Cingulate Cortex is located towards the back of the brain in the highlighted Cingulate Cortex below.
Conscientiousness	Top-down control of behaviour and impulses in order to follow rules and pursue non-immediate goals.	Pre-frontal Cortex; linked to the self-discipline and organisation needed for top-down control.	This brain region is responsible for our ability to plan and follow rules.	The Pre-frontal Cortex
Openness	The tendency to detect, explore, appreciate, and utilise patterns of abstract and sensory information.	Openness consists of intellect (according to DeYoung) i.e. an engagement with abstract and intellectual information. It is this aspect which is linked to the two regions within the Pre-frontal cortex – the Frontal Pole and the Posterior Medial Frontal Cortex.	The Frontal Pole is involved in abstract integration of multiple cognitive operations and in drawing abstract analogies.The Posterior Medial Frontal Cortex is involved in monitoring goal-directed performance and detecting the likelihood of error during cognitive processes.	The Medial Pre-frontal Cortex

*Neurotransmitters – chemicals found in the brain which allow communication between neurons (via synapses).
The pursuit of mapping out personality constructs according to our neuroscience is now possible, because of the huge advances in brain measurement technology. This is a complex yet incredibly exciting and revolutionary undertaking. We are today closer than we have ever been to understanding the intriguing human machine, which lies encased within our primitive skulls. Yet, we stand light-years away from fully understanding it, as we still face many challenges. In relation to personality theory, as DeYoung concludes, we could base a causal theory of personality on psychological constructs alone, but this would be ignoring the neurological basis of behaviour and experience. Perhaps the BRAIN initiative, in time will take us one step closer to comprehending the potential cause of the whole person. Through a more sophisticated understanding of how the various brain systems communicate and function in tandem, we can create a better picture of how such unique and individual personalities emerge.
Written by Raj Chopra, Committee Member, The Psychometrics Forum.
References
DeYoung, C. G. (2010). Personality Neuroscience and the Biology of Traits. Social and Personality Psychology Compass, 4, 1165–1180.
DeYoung, C. G., Quilty, L. C., & Peterson, J. B. (2007). Between facets and domains: 10 aspects of the Big Five. Journal of Personality and Social Psychology, 93, 880–896.
McCrae, R. R., Jang, K. L., Ando, J., Ono, Y., Yamagata, S., Riemann, R., et al. (2008). Substance and artifact in the higher-order factors of the big five. Journal of Personality and Social Psychology, 95, 442–455.
Brain images courtesy of http://www.g2conline.org/