Biochemical Factors

"Better biochemical methods of assessment and growing interest in interdisciplinary research in the field of personality research and individual differences will presumably yield more detailed knowledge about the biochemistry of temperament in the near future"

Numerous theories on temperament constructs rely on biochemical investigations including Zukerman's (1991) sensation seeking, Eyesnk's (1991) extraversion/introversion theory, and Strelau's (1991) temperament dimension based on the pavlovian concept of nervous system strength. Zukerman notes,

Zukerman cautions however,

Because the term temperament has considerable overlap with other dimensions of personality and with emotional and cognitive functions, there are very few studies directed explicitly to the biochemical measurement of tempreament. If, as Netter (1991) suggests, biochemical investigations are based on healthy human subjects, "...they usually start with a trait like extraversion or emotionality and explore the set of biochemical variables most likely associated with this trait (p. 148). In these theories, "...biochemical measures are mainly used for exploration of the psychological construct under investigation with the purpose of elucidating its biological roots" (p. 150).

Netter also notes that modern biological psychiatry also yields,

Benzodiazepine, Serotonin, testosterone, and Monamine Oxidase and their link to temperament have also been investigated. Many theorists have suggested that the neurotransmitter dopamine is the basis of some kinds of general motivational trait involving exploration directed toward primary rewards in animals and novelty and sensation seeking in humans. Aditionally, there are also suggestions of a link to sensation seeking and impulsivity found in the psychoticism dimension (Zukerman, 1991).

Clinical observations of elevated levels of cortisal in some depressed patients, and decreased levels of serotinin metabolite 5-HIAA in cerbrospinal fluid of depressed patients having a history of particularly cruel attempts of suicide led to the theory of genetically low synthesis of serotonin in brain cells in these patients and in psychopaths, alcoholics, and pathological aggressors (Netter, 1991).

As Netter further summarizes, numerous investigators report a great variability in drug response. The underlying basis of which,

There also appears to be some relationship, as example between high type-A personality behavior and coping-induced-related myocardial infarction.

Netter concludes that since temperament is that part of a person's psychological characteristic,

Validity of biocehmical measures, as noted by Netter, are threatened because,

  • Biochemical measures lack specificity...

  • Sensitivity of the parameters depend on methods of assessment.

  • For neutransmitters there is no direct access to brain levels...

  • There is a rapid up-take into the nerve cell, and turnover, the salient parameter, may be hardly accessed.

  • There are many compensatory feedback loops between release of a transmitter and inhibition of its release by stimulation of autoreceptors.

  • There is no one-to-one relationship between a stimulus and a neurottransmitter and a behavioral response...(p.156-157).

    Zukerman (1991) compares today's research for simplicity with the "nineteenth-century phrenology [which] proposes that each personality trait had a particular locus in the brain that shaped the skull above it" (p.129). The new phrenology suggests, "that each personality trait is based on one particular brain structure or system or one biochemical" (p.129).

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    Peter L. Heineman
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