nature and nurture

• the debate


  the debate is about the relative contribution of genetic inheritance (nature) and environmental factors (nurture)
• interactionist approach


  all characteristics combine nature and nurture e.g. attachment can be explained in terms of quality of parental love (Bowlby 1958) or child's temperament (Kagan 1984) and heredity interact
• diathesis-stress model


  in the diathesis-stress model, behaviour is caused by a biological/environmental vulnerability which is only expressed when couple with a biological/environmental trigger e.g. a person who inherits a genetic vulnerability for OCD may not develop the disorder. But, combined with a psychological trigger e.g. a traumatic experience this may result in the disorder appearing
• epigenetics


  a change in genetic activity without changing the genetic code

  - lifestyle and events we encounter e.g. smoking, diet, trauma leave 'marks' on our DNA - switching genes on or off

  - this has a lifelong influence and can be passed onto future generations
• nature


  early nativists e.g. Descartes 17th century argues that human characteristics are innate - the results of our genes

  - psychological characteristics e.g. intelligence or personality are determined by biological factors just like eye colour or height
• nurture


  empiricists e.g. Locke 17th century argues the mind is a blank slate at birth, and is shaped by interaction with the environment e.g. the behaviourist approach

  Lerner (1986) identified different levels of the environment:

  - prenatal terms e.g. mother smoking or hearing music

  - postnatal experiences e.g. the social conditions a child grows up in
• measuring nature and nurture

  concordance - the degree to which two people are similar on a particular trait

  heritability - proportion of differences between individuals in a population, with regards to a particular trait, due to genes. 0.01% (1%) is very little contribution, 1.0% (100%) means genes are the only reason

  - the figure for heritability in IQ is about 0.5 (Plomin 1994)
• strength


  P - adoption studies

  E - if adopted children are more similar to their adoptive parents, suggests environmental influence, if more similar to biological parents, suggests genetic influence

  E - Rhee and Waldman (2002) found in a meta-analysis of adoption studies that genetic influences accounted for 41% of variance in aggression

  L - this shows how research can separate nature and nurture influences

  COUNTERPOINT

  - children create their own nurture by selecting environments appropriate to their nature - a naturally aggressive child will choose aggressive friends and become more aggressive

  - this suggests that it does not make sense to look at evidence of either nature or nurture
• strength


  P - support for epigenetics

  E - in 1944, the Nazis blocked the distribution of food to the Dutch people and 22,000 died of starvation (the Dutch Hunger Winter

  E - Susser and Lin (1992) found that women who became pregnant during the famine had low birth weight babies who were twice as likely to develop schizophrenia

  L - this suggests that the life experiences of previous generations can leave epigenetic 'markers' that influence the health of their offspring
• strength


  P - real world application

  E - Nestadt et al (2010) put the heritability rate at .76 for OCD i.e. it is highly heritable. Such understanding can inform genetic counselling

  E - people who have a high genetic risk of OCD because of their family background can receive education about inheritance, management and prevention of the disorder

  L - this shows that the debate is not just about theoretical but that it is also important, at a practical level, to understand the interaction between nature and nurture
• strength/limitation


  P - implications of the debate

  E - the extreme nativist stance is determinist and has led to controversy e.g. linking ethnicity, genetics and intelligence and eugenic policies

  E - empiricists suggest that any behaviour can be changed by altering environmental conditions e.g. aversion therapy. This may lead to a society that controls and manipulates its citizens

  L - this shows that both positions, taken to extremes, may have dangerous consequences for society so a moderate, interactionist position is preferred