nature-nurture debate

• nature

  • early nativists (eg Descartes) argued that human characteristics are innate - the result of our genes
  • psychological characteristics (eg intelligence/personality) are determined by biological factors - just like our eye colour or hair
  • 'inherited influences'
• nurture

  • empiricists (eg Locke) argued that the mind is a blank slate at birth and is shaped by interaction with the environment (eg behaviourist approach)
  • Lerner = identified different levels of the environment:
  • prenatal terms = eg mother smoking or hearing music
  • postnatal experiences = eg 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%) = very little contribution
  • 1.0(100%) = means genes are the only reason
  • Plomin = figure for heritability in IQ is about 0.5
• interactionist approach

  • the view that the processes of nature and nurture work together rather than in opposition - linked in such a way that it does not make sense to separate the influences of the two
  • not really a debate because all characteristics combine nature and nurture - even eye colour is only .80 heritable
  • eg = attachment can be explained in terms of quality of parental love (Bowlby) or child's temperament (Kagan) - environment and hereditary interact
• diathesis-stress model

  • behaviour is caused by a biological/environmental vulnerability (diathesis) which is only expressed when coupled with a biological/environmental trigger (stressor)
  • eg = a person who inherits a genetic vulnerability for OCD may nit develop the disorder - BUT combined with a psychological trigger (eg a traumatic experience) this may result in the disorder appearing
• epigenetics

  • epigenetics = a change in genetic activity without changing the genetic code
  • lifestyle and events we encounter (eg smoking, diet, trauma) leave 'marks' on our DNA (genes) - switching genes on or off
  • this has a lifelong influence and can be passed on to future generations
• twin studies

  • MZ twins share 100% of genes but DZ twins only 50% (on average)
  • so we would expect a greater likelihood of both MZ twins developing the same behaviour if it is mostly genetic
  • because both MZ and DZ twins are raised together in the same environment BUT MZ twins have a greater degree of genetic similarity thaN DZs
• strength = research in adoption studies

  • if adopted children are more similar to their adoptive parents = suggests environmental influences
  • if more similar to biological parents = suggests genetic influence
  • Rhee and Waldman = found in a meta-analysis of adoption studies that genetic influences accounted for 41% of variance in aggression
  • shows how research can separate nature and nurture influences
• counterpoint to adoption studies

  • children create their one nurture by selecting environments appropriate to their nature (niche-picking)
  • a naturally aggressive child will choose aggressive friends and become more aggressive
  • suggests that it doesn't make sense to look at evidence of either nature or nurture
• strength = support for epigenetics

  • in 1944 = the Nazis blocked the distribution of food to the dutch people and 22000 died of starvation (the Dutch Hunger Winter)
  • Susser and Lin = found that women who became pregnant during the famine had low birth weight babies who were 2x likely to have schizophrenia
  • suggests that the life experiences of previous generations can leave epigenetic 'markers' that influence the health of their offspring
• strength = RWA

  • Nestadt et al = put the heritability rate at .76 for OCD (ie it is highly heritable)
  • such understanding can inform genetic counselling
  • people who have a high genetic risk of OCD because of their family background can receive education act inheritance, management and prevention of the disorder
  • shows that the debate is not just theoretical but it is also important at a practical level to understand the interaction between nature and nurture
• extra evaluation = implications of debate

  • the extreme nativist stance is determinist and has led to controversy = eg linking ethnicity, genetics and intelligence, and eugenic policies
  • empiricists suggest that any behaviour can be changed by altering environmental conditions (eg aversion therapy)
  • this may lead to a society that controls and manipulates citizens
  • shows that both positions (taken to extremes) may have dangerous consequences for society => a moderate interactionist position is preferred