Controversies - Gentics Vs Environment:


Schizophrenia - Twin Studies:

  • The role of genetic influences is demonstrated by research on schizophrenia. Evidence from twin studies, E.G. Joseph, suggests that the genetic component for schizophrenia is stronger than for unipolar depression but less than for bipolar disorder because there are higher concordance rates for MZ twins, than DZ twins.
  • One problem is that MZ twins may share more similar environments than DZ twins, so it is difficult to seperate the effects of genetics from the effects of the environment.
  • Although twin studies support a genetic component to schizophrenia, the fact that concordance rates are not 100% means that there must also be environmental factors.
  • Evidence suggests there are important environmental influences because a person from a lower socioeconomic group or someone who has major life stressors will be at a higher risk of developing schizophrenia. This evidence relies on retrospective data and correlations, a criticism is that this evidence may not be reliable, also not possible to infer a cause & effect relationship.
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Schizophrenia - Twin Studies: No.2

  • In conclusion, evidence suggests that both genetics and the environment are important. However, the diathesis stress model suggests that environmental factors may trigger mental illnesses,but only in people that already have a genetic disposition for it.
  • In support of this, Tienari found that adopted children of schizophrenic parents only developed it if their adoptive family was a disturbed one. Suggests that genes are more important than the environment but both are necessary to trigger it.
  • These genetic influences could explain neurological and neurochemical abnormalities such as excess dopamine found in schizophrenia.
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  • Difficult to see how criminality can be influence by genetics because what is considered to be a crime is determined by culture and context. E.G. It is a crime to kill another person, but not if this is done in the context of war. In many western cultures, female circumcision is illegal, but not in all cultures.
  • However, is it possible that genetic influences may play a role in intelligence, morality and aggression which may indirectly affect the likelihood that somebody will break the law.
  • Family & adoption studies suggest that genetic influences are more important than up-bringing when it comes to criminality because children with a biological parent who has a criminal record are more likely to commit crimes than children who are adopted by a parent with a criminal record.
  • Certain genes, such as the NOS1 gene have also been linked with aggression in humans, which suggests that there may be a genetic component to crimes of violence.
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Environmental influences:

  • Role of environmental influences is supportewd by Bandura's social learning theory and his BoBo doll experiment.
  • One problem is that laboratory experiments, like Banduras may not represent real life acquisitions of criminal behaviour, therefore they may lack ecological validity.
  • However, natural experiments have also found correlations, which support the role of the media in learning anti-social behaviour. However, its not possible to infer a cause and effect relationship from a correlation.
  • In conclusion, anti-social and aggressive behaviours may be hard-wired into our biology, increasing the likelihood that an indiviual will commit a crime, but these interact with environmental influences to determine whether an individual will behave criminally.
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  • Been shown by many studies that genetics play an important role in development.
  • Environmental factors have been shown to trigger certain behaviours and to activate particular genes (i.e. diathesis stress model). Suggests that both genes and environment are entwined.
  • However, the balance of genes and environment differs from each issue. E.G. In schizophrenia, genetics may be more influential than the environment, whereas for criminality, evidence would suggest that environmental influences are much more important.
  • After years of trying to seperate the two, psychologists are beginning to realise how closely the two are inter-related.
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