Introduction

Personality is defined as a distinctive constellation of relatively stable behaviors, thoughts, motives, and emotions that characterize a unique individual. Personality organization derives from the interaction between the individual and social learning as well as an internal set of motivated predispositions to respond. Cloninger et al. (1993) have developed a biosocial model of personality describing four dimensions of temperament genetically dependent and stable and three dimensions of character that are influenced by social learning. The four dimensions of temperaments include:

1. novelty seeking, describing genetic dispositions towards being excitable, impulsive, exploratory, and quick-tempered

2. harm avoidance, related to behavioral inhibition, implying a heritable bias towards being cautious, apprehensive, and pessimistic

3. reward dependence, involving the maintenance of behaviors previously associated with reinforcement

4. persistence, describing the ability to persevere despite fatigue or lack of reward.

The three dimensions of character are:

1. self-directedness, implying an autonomous self-concept and feelings of hope and self-confidence

2. cooperativeness, involving identification with and acceptance of others, and compassion

3. self-transcendence, related to spirituality, patience, and self-forgetfulness.

Cloninger et al. (1993) hypothesized that each temperament dimension is regulated neurochemically by a complex distributed network of brain connections. Novelty seeking has been associated with dopaminergic activity, harm avoidance with serotonergic activity, and reward dependence with noradrenergic activity. Youn et al. (2002) observed that each temperament dimension is correlated with regional cerebral glucose metabolism in specific areas of paralimbic regions and temporal lobes. These findings provide further evidence that temperament dimension is associated with specific brain areas and neurotransmitters.