The Nature-nurture Debate

Nature: behaviour is the product of innate biological/genetic factors
- Result of heredity
  - Genetic transmission of mental/physical characteristics from one generation to another
  - Heritability coefficient: number 0-1, extent to which characteristic has a genetic basis
    - g. Plomin (1984) IQ is around 0.5, both genes and the environment are important factors
  - Genetic explanations
    - Family/twin/adoption studies show a link between genetic similarity and shared characteristics/behaviour
  - Evolutionary explanations
    - Behaviour/characteristics that aid survival will be naturally selected
    - Genes passed on to future generations

Nurture: behaviour is the product of environmental forces
- Behaviourism: the mind is a blank slate at birth upon which experience writes
- Lerner (1986): different levels of the environment
  - Prenatal terms
    - g. mother’s physical/psychological state during pregnancy
  - Postnatal experiences
    - g. the social conditions a child grows up in
  - g. behaviourism
    - suggested attachment could be explained in terms of classical (who feeds them) and operant (reward of reduced hunger) conditioning
  - g. SLT: Bandura
    - Vicarious reinforcement but biology plays a role
    - Having the urge to behave aggressively (biological) but learn to express anger through environmental influences (direct/vicarious reinforcement)

Relative importance of nature and nurture
- Debate impossible to answer because environmental influences begin at conception (or earlier)
- Makes little sense to separate the two
  - g. concordance rates: difficult to tell whether they are the result of shared genetics or shared upbringing

Interactionist approach
- Studies how nature and nurture interact and influence each other
- g. sees attachment to parent as a ‘two-way street’ (Belsky + Rovine 1987)
  - Child’s innate temperament influences how parent behaves towards them
  - Parent’s responses in turn affect the child’s behaviour
- Nature creates nurture

Interactionism in mental illness: Diathesis-stress model
- Caused by a biological vulnerability only expressed when coupled with an environmental trigger
- g. Tienari et al (2004)
  - Orphan study
  - High risk of schizophrenia: biological relatives with a history of the disorder and adoptive family classed as dysfunctional

Interactionism: epigenetics
- Change in genetic activity without a change in genetic code
- Lifestyle/events leave ‘marks’ on our DNA
  - Tell our bodies which to ignore and which to use
  - May influence genetic code of offspring
    - g.Dias + Ressler (2014)
      - Mice given an electric shock when they smelt a certain chemical
      - Showed a fear response
      - Fear response also present in children and grandchildren who had never experienced the shocks
    - Epigenetics introduced a third element into the debate (life experiences of previous generations)

Confounding factor of shared environments
- Research trying 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 (1990(
  - Individual differences mean siblings may experience life events differently
    - g. age/temperament leads to life events (e.g. parental divorce) having a different meaning to each sibling
  - Explains finding that even MZ twins reared together do not show perfect concordance rates

Gene-environment interactions explained by constructivism
- People create their own nurture by actively selecting environments appropriate for their nature
  - Interaction known as constructivism
  - g. a naturally aggressive child will feel more comfortable around similar children and chooses their environment accordingly
    - This then effects their development
    - Plomin (1994) called it niche-picking and niche-building
  - Constructivism shows it is impossible/illogical to separate nature and nurture influences on a child’s behaviour

Evidence for the gene-environment interaction
- Scarr and McCartney (1993)
  - Three types of gene-environment interaction
    - Passive
    - Evocative
    - Active
  - Interaction is different for each type
    - g. passive: parents genes influence how they treat their children
      - g. musically gifted parents play to their children and encourage love of music
    - Complex/multi-layered relationship between nature and nurture