Genetics vs. Environment


Genetic Examples

  • Intelligence

    • Piaget (1954) intelligence is innate at birth but develops at different stages through biological maturation (different things become available at different ages)

    • Largely genetic component

    • Flynn effect – IQ has overall gone up by 20 points in the last 30 years, showing a clear environmental impact

    • Turkheimer et al (2003) 60% of variance in affluent families is due to genes, however, in poorer families, it could account for no variance, showing clear environmental impact

  • Mental Illness

    • Joseph (2004) 40.6% concordance for schizophrenia in MZ twins

    • Tienari et al – adopted children with schizophrenic mothers are still more likely to have schizophrenia

    • Must be some environmental influence or we would expect 100% concordance

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Genetic Examples Continued

  • Evolutionary

    • Natural selection theory, traits which benefit our survival are passed on

    • Fight or Flight response

    • Selye (1936)

    • Buss – mating choice is universal, modified by culture

  • Influences

    • Active influence – children seek out experiences to suit their genes, e.g. a predisposed genetically aggressive child will seek to be aggressive

    • Passive influence – parents genes effect the environment they create for their children e.g. schizophrenic parents are emotionally flat towards their children causing them to become schizophrenic

    • Reactive influence – genes directly change the environment

  • Phenylketonia

    • Inherited genetic disorder affecting amino acids

    • Controlled by diet

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Implications of the Genetic Argument

  • Politics

    • Selective human breeding if nature is correct - Hitler

    • Engineering correct behaviour is environment is correct – Pol Pot

    • Massive ethical issues in deciding upon which is correct

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Environmental Examples

  • Nurture

    • Due to behavioural learning, interaction and experience

  • Aggression

    • SLT – Bandura (1961)

    • This theory doesn’t ignore biology, it recognises that a potential for aggression is genetic whilst expression of aggression is learnt

  • Neural Plasticity

    • Maguire et al (2000) London Taxi drivers have enlarged hippocampi, showing how their brains have developed for more spatial awareness and planning

    • Edwards and Cline (1999) neurones shrink and grow in response to environmental change

    • Blakemore and Cooper – Kitten study

  • Environmental Inheritance

    • Epigenetics – genes are turned on and off due to our environment

      • Why clones don’t produce exact copies

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