Abnormal Psychology

Understanding Psychological Disorders: The Neuropsychosocial Approach 59

half of the variability in temperament (Oniszcenko et al., 2003). Researchers have

associated some aspects of temperament to specifi c genes, such as genes that affect

receptors for the neurotransmitter dopamine and a gene involved in serotonin pro-

duction, and have shown that these genes can infl uence depression and problems

controlling impulses (Nomura et al., 2006; Propper & Moore, 2006). Genes that

affect dopamine receptors have also been shown to infl uence emotional reactivity

(Oniszczenko & Dragan, 2005). However, these genes have stronger effects on chil-

dren raised in harsh family environments, and, as we stressed earlier, the effects of

genes need to be considered within the context of specifi c environments (Roisman &

Fraley, 2006; Saudino, 2005).

Researchers and scholars going back at least as far as Plato in ancient Greece

have proposed many ways to conceive of variations in temperament (Buss, 1995;

J. A. Gray, 1991; Eysenck, 1990). C. Robert Cloninger and his colleagues have

proposed one particularly infl uential contemporary theory of temperament, which

describes temperament in terms of four dimensions—novelty seeking, harm avoid-

ance, reward dependence, and persistence—each of which is associated with a brain

system that relies predominantly on a particular neurotransmitter (Cloninger, 1987;

Cloninger, Svrakic, & Przybeck, 1993).

Novelty seeking consists of searching out novel stimuli and reacting to them

positively; this dimension of temperament also involves being impulsive, avoid-

ing frustration, and losing one’s temper easily. Novelty seeking is thought to be

associated with the actions of dopamine (which is known to play a central role in

the effects of reward on behavior). A high level of novelty seeking is associated

with a variety of disorders that involve impulsive or aggressive behaviors (Yoo

et al., 2006).

Harm avoidance consists of reacting very negatively to harm and, whenever

possible, avoiding it. This dimension of temperament may be associated with the ac-

tions of serotonin (which, as noted earlier, is involved in mood and motivation). For

instance, people with anxiety disorders tend to have higher levels of harm avoidance

than do people without anxiety disorders (Ball, Smolin, & Shekhar, 2002; Rettew

et al., 2006; Wiborg et al., 2005).

Reward dependence involves the degree to which behaviors that have led to

desired outcomes in the past are repeated; for example, a person may continually

seek out social approval because he or she has received approval in the past. This

dimension of temperament is associated with the actions of norepinephrine (which

plays a role in attention and the stress response). A low level of reward dependence,

in combination with a high level of impulsivity, is found in people who have sub-

stance use disorders (Tcheremissine et al., 2003).

The fourth dimension of temperament is persistence, which consists of making

continued efforts in the face of frustration when attempting to accomplish some-

thing. Originally, this dimension was viewed as an aspect of reward dependence

(and hence affected by norepinephrine), but subsequent research has suggested

that certain genes that lead to low levels of dopamine may be associated with it

(Czermak et al., 2004). A low level of persistence is found in attention-defi cit/hyper-

activity disorder (Yoo et al., 2006).

In fact, researchers have found associations between specifi c genes and these

dimensions of temperament (Gillespie et al., 2003; Keltikangas-Järvinen et al.,

2006; Rybakowski et al., 2006). The specifi c results suggest that complex inheri-

tance, not Mendelian inheritance, is at work. Temperament apparently arises from

the joint activity of many different factors. However, not surprisingly, the underly-

ing neurological bases for the four dimensions of temperament are more complex

than originally conceived. For example, researchers have linked novelty and reward

dependence with certain genes and with levels in the blood of a specifi c variant of

monoamine oxidase (MAO), an enzyme (Shiraishi et al., 2006); people who have

low levels of MAO tend to seek out sensations by engaging in high-stimulation

activities, such as sky diving (Zuckerman, 1994).

Because of temperament, some people will avoid

situations that have a risk of harm. Such people

are more likely to have high levels of anxiety and

to develop anxiety disorders.

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