My mind, my thoughts, my words

Biological Foundations of Personality Traits (Genes, Physiology, Evolution) (P4)

Two obsessions seem to be going around:

phrenologyBRAIN obsession: e.g. Phineas Gage’s personality changed dramatically after his brain was damaged, and Franz Gall allocated aspects of personality (emotional and behavioural) to parts of the brain (‘Phrenology’). Inhibited kids have been shown to have higher amygdala reactivity and respond more to novel situations. Also, the volume of grey matter has been associated with personality traits.

BODY obsession: this one was new to me, but apparently (I think my lecturer’s word is quite credible), people attribute different personalities to different body types. Kretschmer came up with three body types; plump people (more extroverted and prone to suffer depression), muscular, and frail (more likely to be introverted and suffer schizophrenia).

There are 2 types of biological causes of a behaviour

1) Proximate: biological processes at the time of a behaviour

2) Ultimate: historical view; ultimate cause explanation (evolutionary adaptions that help with survival and reproduction)

Psychopharmocology of Personality

As we can alter personalities with drugs (in particular those that affect the dopamine system, e.g. anti-psychotic drugs), there is likely to be a relationship between neurotransmitters and personality. Links that have been found:

  • low dopamine: novelty seeking
  • serotonin levels: harm avoidance
  • noradrenaline levels: reward dependence
  • (MAO >) dopamine > positive affect > expect reward > active, sociable behaviour > Extroversion
  • Dopamine >disinhibition > sensation-seeking > Impulsiveness
  • MAO/adrenaline > cortical excitation > disinhibition > sensation-seeking > Impulsiveness
  • Adrenaline > adrenergic arousal > Hostility
  • Adrenaline > adrenergic arousal > aggression, anger/anxiety > expect punishment > emotional > Neuroticism
  • GABA > anxiety > expect punishment > emotional > Neuroticism

Personality and Genes

An individual’s personality is composed of three factors

  1. genes (40% variation)
    Identical twins not reared together (e.g. Minessota Twin Study MSTRA): same genes, different unique and shared environments – demonstrates the importance of genes! Genes seem to be more important for determining personality than environment!
  2. unique environment (more important for personality; 35% of variation in personality is due to it)
    Identical twins reared together: same genes, shared environment, but unique environments that make them distinct
  3. shared environment (5% variation)
    Siblings reared together: same shared environment, different unique environments and genes

A Dunedin Study on violence found that the interaction of genes and environment may be important; the gene MAOA was only switched on when children were subject to maltreatment. More specifically, the interaction here is nature VIA nurture.

Biological Processes and Personality Traits

Biological components have been associated with more than one trait – one trait is influenced by more than one biological factor.

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This entry was posted on 16/04/2013 by in Psychological Issues and tagged , , , .
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