The nature-nurture debate

• Nature: innate and genetic influences, usually 0.5 heritability
• Early nativists (e.g. Descartes) argued that human characteristics are innate- the result of heredity
• The general figure for heritability of IQ is around 0.5. The fact this is not 1.0 (100%) suggests that genetics and the environment are both important factors in IQ
• Nurture: environmental influences (e.g. learning and experience pre- and postnatal)
• Empiricists (e.g. Locke) argued the mind is a blank slate at birth upon which experience writes- the behaviourist approach
• Lerner has identified different levels of the environment (Nurture):

  • Defined in narrow prenatal terms (e.g. the mother's physical and psychological state during pregnancy)
  • Defined more generally through postnatal experiences (e.g. the social conditions the child grows up in)
• The nature-nurture debate is impossible to answer because environmental influences in a child's life begin as soon as it is conceived (perhaps even earlier)
• Practically and theoretically it makes little sense to try to separate nature and nurture (e.g. in twin studies it is difficult to tell whether high concordance rates are more the result of shared genetics or shared upbringing)
• The focus of the debate is now on the relative contribution of each influence
• For example, the interactionist approach to attachment sees the bond between infant and parent as a 'two-way street':

  • The child's innate temperament influences how the parent behaves towards them
  • The parent's responses in turn affect the child's behaviour
• What are three examples of when interactionism can be seen?

  • Attachment
  • The diathesis-stress model
  • Epigenetics
• The diathesis-stress model suggests mental disorder is caused by a biological vulnerability (diathesis) which is only expressed when coupled with an environmental trigger (stressor)
• Interactionism- epigenetics:

  Epigenetics is a change in genetic activity without changing the genetic code. Lifestyle and events we encounter (e.g. smoking, diet, pollution, poverty) leave epigenetic 'marks' on our DNA- these marks tell our bodies which genes to ignore and which to use, and may influence the genetic code of our children
• Strength: real-world implications

  Extreme beliefs in the influence of nature or nurture may have negative implications for how we view human behaviour. Nativists suggest genes determine behaviour and characteristics ('anatomy is destiny'). This has led to controversy (e.g. linking race to eugenics policies, and advocating a model of society that manipulated its citizens). Recognising that human behaviour is both nature and nurture is a more reasonable way to approach the study and 'management' of human behaviour
• Limitation: confounding factor of unshared environments

  Research that tries to 'tease out' environmental influences is complicated by the fact that even siblings raised within the same family will not have identical upbringings- there are shared and unshared environments. Dunn and Plomin suggest individual differences mean siblings may experience life events differently. This would explain the finding that even MZ twins reared together do not show perfect concordance rates.
• Strength: evidence for gene-environment interaction

  Scarr and McCartney outline three types of gene-environment interaction: passive, evocative and active. The interaction is different for each type- e.g. in passive interaction, parent's genes influence how they treat their children (musically-gifted parents play to their children and encourage love of music)
• Strength: understanding nature-nurture relates to other debates

  A strong commitment to either a nature or nurture position corresponds to a belief in hard determinism. The nativist perspective suggests 'anatomy is destiny' whilst empiricists argue that interaction with the environment is all. These equate to biological determinism and environmental determinism, showing how nature-nurture links to other debates