PSY224 Biological basis of personality

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PSY224 Biological basis of personality
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Reading

• Chapter 6 suggested reading
• theres PLENTY in the journals
• You may also want to consult
• Zuckerman, M. (1991) Psychobiology of
  Personality
• or Matthews Deary (1998)

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Aims Objectives

• By the end of this lecture you should-
• understand 4 reasons why its important to
  understand the biological basis of personality.
• know how the biological basis of personality
  might be established.
• be able to marshal evidence for the biological
  roots of Extraversion

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Why a biological approach?

• Because its easier! Social theories may use
  vague terms (actualisation) that are
  difficult/impossible to measure accurately.
• Most experimental designs in social psychology
  overlook the possibility of genetic
  predispositions towards (e.g.) aggression.
  Identification.
• Difficult to measure social interactions

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• Behaviour-genetic studies (to be considered
  later) show that most personality traits have a
  genetic component. Influences outside the family
  also shape personality. The family itself has
  far less influence than most people imagine
  possible.

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Benefits of developing biological models

• (1) Do personality traits reflect real causal
  influences ? Or are they artefacts of factor
  analysis bloated specifics etc? Or is it
  situations (not traits) that determine behaviour?
  (Mischel) If reliably linked to physiology of
  the nervous system, genes etc. these objections
  cant be valid.

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• (2) Circularity. We need to show that traits
  exist in domains other than those used to measure
  them in order to refute objections of circularity.

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• (3) Need to understand personality processes.
  Personality development. Why are personalities
  different? Upbringing/environment? Role models?
  Physiology?

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• may show areas where personality should interact
  with other branches of the subject. If tied to
  physiology, it may be vital to consider
  personality in many branches of psychology. E.g.
  learning, pharmacology, motivation, perception,
  cognition..... Personality can be a MARKER for a
  given type of brain structure

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Theories

• Eysenck (1967) The Biological Basis of
  Personality.
• Recall that-
• E sociable, lively, active, assertive,
  sensation-seeking, carefree, dominant,
  venturesome
• N anxious, depressed, guilt feelings, low
  self-esteem, tense, irrational, shy, moody,
  emotional
• P aggressive, cold, egocentric, impersonal,
  impulsive, antisocial, unempathetic, creative,
  tough-minded

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Eysenck (1967, 1985) on Extraversion

• Introverts are more cortically aroused than
  extraverts, so need less external stimulation.
  Ascending Reticular Activating System (ARAS)
  implicated in-
• initiation maintenance of emotion,
• motivation conditioning,
• attention, arousal and orienting behaviour
• The theory was later (1990) modified so that the
  limbic system explained arousal.

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Extraversion, arousal and hedonic tone
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Eysenck on Neuroticism

• Autonomic nervous system reactivity (flight or
  fight) "Visceral brain". Physiological
  structures relating to neuroticism are to do with
  emotion.

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Eysenck on Psychoticism

• Hormones, neurotransmitters and enzymes that
  influence impulsivity inhibition

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Experimental evidence for a biological model

• Genetic analyses (see later)
• Psychophysiological data
• Psychopharmacology
• Cross-cultural studies
• Cross-species studies

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Psychophysiological correlates of Extraversion

• The EEG (electroencephalogram)
• resting extraverts should show less cortical
  arousal (alpha activity) than introverts. They
  do seem to (Gale, 1983 meta-analysis)
• resting extraverts should show more delta/theta
  activity (they do Matthews Amelang, 1993)

Alpha 7.5-14Hz Beta gt14 Theta 3.5-7.5 Delta lt 3
Hz (or waves per second)
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• Auditory Evoked potentials. Introverts brains
  react faster to a tone. Mixed findings - age and
  tone frequency confuse matters (Haier Robinson
  Braden Williams, 1984 Stelmack Houlihan,
  1995). Also reliable personality-related
  differences to later parts of the wave - update
  of working memory?

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• Introverts have larger, faster-dilating pupils
  (Stelmack Mandelzys, 1975).
• Sedation thresholds. Introverts need more
  barbiturate to "make them unconscious".
  (Claridge, Donald Birchall, 1981). (But an
  interaction with N).

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Psychopharmacology

• E may be related to dopamine pathways which
  control positive motivation and approach
  behaviour in animals. Not well supported.

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Cross-cultural studies

• Are E,N,P found in all cultures?
• Yes. (e.g. Eysenck, 1982).

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Cross-species studies

• Are PEN found in non-human animals?
• Stevenson-Hinde et al (1980) find confidence,
  excitability sociability when rating rhesus
  monkeys.

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Problems for the theory

• Brain damage to frontal lobes affects arousal,
  but NOT E! (Zuckerman, 1991)
• Others (e.g., Blakemore, 1967) comment on the
  theorys indifference to lateralisation.
• Problems in replicating psychophysiological
  studies

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Overview

• Overall there "is a good deal of evidence that
  introverts are characterized by greater
  physiological reactivity to sensory stimulation
  than extraverts ... but there is little
  compelling evidence that introverts and
  extraverts differ in tonic or basal levels"
  (Stelmack, 1990 p 307).