nature nurture debate

• Interactionist approach

  It is not really a debate because all characteristics combine nature and nurture (even eye colour is only .80 heritable). For example attachment can be explained in terms of quality of parental love (Bowlby 1958) or child's temperament (Kagan 1984). Environment and heredity interact.
• Diathesis - stress model

  In the diathesis-stress model behaviour is caused by a biological/environmental vulnerability (diathesis) which is only expressed when coupled with a biological/ environmental trigger (stressor). For example, 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

  Epigenetics is a change in genetic activity without changing the genetic code. Lifestyle and events we encounter (e.g. smoking, diet, trauma, war) leave 'marks' on our DNA (genes) - switching genes on or off. This has a lifelong influence and can be passed on to future generations.
• Nature

  Early nativists (e.g. Descartes, 17th century) argued that human characteristics are innate - the result 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) argued 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).
• Evaluation

  One strength in nature nurture research is adoption studies. If adopted children are more similar to their adoptive parents, suggests environmental influence, if more similar to biological parents, suggests genetic influence. Rhee and Waldman (2002) found in a meta-analysis of adoption studies that genetic influences accounted for 41% of variance in aggression. This shows how research can separate nature and nurture influences.
• Evaluation

  One strength is support for epigenetics. In 1944, the Nazis blocked the distribution of food to the Dutch people and 22,000 died of starvation. 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. This suggests that the life experiences of previous generations can leave epigenetic ‘markers' that influence the health of their offspring.