BIOLOGICAL PROCESSES AND

PERSONALITY

Eysenck was one of the first personality theorists to link personality variables to brain processes. Extraversion was linked to cortical arousal in the Ascending Reticular Activating System such that:

Extraverts had Low Cortical Arousal

Introverts had High Cortical Arousal

Also, Neuroticism was linked to Autonomic Activation (located in the ) such that:

Hi Neuroticism had High Autonomic Activation, and Low Neuroticism had Low Autonomic Activation.

In the last 2 decades, researchers have learned many new things about brain function, so Eysenck’s work is no longer contemporary, but he did lead the way to today’s current theorizing and research about:

the BEHAVIORAL APPROACH SYSTEM (BAS), and the

BEHAVIORAL INHIBITION SYSTEM (BIS).

The BAS, located in the left pre-frontal portion of the brain is thought to be responsible for activation of behaviors that are related to reward-seeking, i.e., pursuit of positive incentives. Greater left pre-frontal brain activity is associated with a) more frequent positive emotions b) a greater tendency to approach reinforcements, and stronger conditioning by reinforcement. Less left pre-frontal brain activity is associated with less emotional and behavioral responding to potential reinforcers. The neurotransmitter DOPAMINE is thought to be involved in the BAS.

The BIS, located in the right pre-frontal portion of the brain is thought to be responsible for activation of behaviors that are related to restraint, i.e., withdrawal from aversive stimuli or avoidance of potential dangers. Greater right pre-frontal brain activity is associated with a) more frequent negative emotions like anxiety and depression, b) a greater sensitivity to threat, and stronger escape and avoidance conditioning. Less pre-frontal right brain activity is associated with less emotional and behavioral responding to potential punishers. The neurotransmitter SEROTONIN is thought to be involved in the BIS.

The exact mechanisms of how these neurotransmitters work is not clear. For example, it is unknown whether the amount of the neurotransmitter is important, or the sensitivity of the receptors, or both.

Theorists have speculated that extraversion may be related to the BAS and that neuroticism may be related to the BIS.

Richard Davidson and his colleagues at UW-Madison have shown that people diagnosed with depression tended to have asymmetrical EEGs, reflecting low left hemisphere pre-frontal activity and high right hemisphere pre-frontal activity.

Also, the most common drugs for depression are known as SSRIs (Serotonin Specific Reuptake Inhibitors), which function to prevent the depletion (re-uptake) of depression in the cells, thus making more available for transmission. The actual mechanism of how SSRIs alleviate depression is unknown, however.