The Biological Approach - The role of genetics

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  • The Biological Approach - The role of genetics
    • 3 basic assumptions - behaviour explained by hormones, genetics, evolution + the nervous system.
    • Genetics
      • Conception - egg + sperm join to give 46 chromosomes. Each is made up of coil of DNA which is made up of genes.
        • Darwin's theory of evolution - over time  individuals who were better adapted to their environment had better genes = more likely to survive + reproduce, passing on useful genes.
          • Those less well-adapted = less likely to survive to reproduce + pass on genes. = less useful genes eliminated from gene pool.
          • Natural selection = humans became better adapted to environment.
            • Behaviours (phobias + aggression) evolved = the survival advantage they gave.
      • Phenotype = the characteristics that a person's genes produce.
      • Genotype = genes a person has.
      • Genetics can explain Psychological traits
        • Faulty genes = diseases that have psychological effects.
    • Twin Studies
      • Identical twins share 100% of their genes
        • Non- identical twins share 50% of their genes = risk of both suffering should be lower than with identical.
      • Gottesman (1991) - A meta-analysis of twin studies
        • Carried out meta-analysis of approx. 40 twin studies
          • Results: Having identical twin with schizophrenia = 48% chance of developing it. 17% in non-identical.
            • Schizophrenia has strong genetic basis.
            • So may have been another factor involved = family environment? Identical treated more similarly than non.
          • Meta-analysis carried out on field studies - high ecological validity.
    • Adoption Studies
      • Heston (1966) - Adoption study of schizophrenia
        • 47 adopted children with schizophrenic mothers studied. Control group = 50 adopted children with mothers who didn't suffer from schizophrenia.
          • Children followed up as adults + interviewed = given intelligence and personality tests.
        • Of experimental group = 5/47 became schizophrenic. Control group = 0. 4 of experimental group = classified as borderline schizophrenic.
        • Supports that schizophrenia has genetic basis.
        • Interview data = unreliable + affected by social desirability bias.
          • But interviews are good way of getting data in naturalistic way.
            • Children whose mothers didn't suffer from any conditions may not have shown symptoms yet


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