Nature- nurture debate

• Nature:

  • Human characteristics are innate
  • Determined by genes
  • Behaviours/characteristics are the result of heredity (genetic transmission of mental and physical characteristics from one generation to another)
  • The degree to which two people are similar on a particular trait can be represented by concordance rates.
• Nature:

  • concordance rate is used to assess heredity (how genetic something is).
  • It is a numerical figure ranging from 0% to 100% which indicates the extent to which a characteristic has a genetic basis (100% means it is entirely genetically determined)
  • Coccaro et al. (1997) found concordance rates of 50% MZ twins and 19% for DZ twins for physical assault. This means that physical assault is half caused by genetics (nature) and half environmental factors (nurture).
• Nurture:

  • Mind is a ‘blank slate’ at birth (e.g. the view of behaviourist psychologists)
  • Behaviour is learnt through interactions with the environment/experiences
  • Concept of nurture requires further clarification as ‘environment’ is a broad term
  • E.g. mother’s physical and psychological state during pregnancy or general experiences as the child grows up and the social/cultural conditions they grow up in
• Examples on the influence on nature:

  Genetic explanations:

  • Family, twin and adoption studies show that the closer two individuals are genetically, the more likely that both of them will develop the same behaviours
  • E.g. concordance rate for schizophrenia is about 40% of MZ twins and 7% for DZ twins 
  • This closer similarity for individuals who share 100% of their genes shows that nature has a major contribution in this disorder
• Evolutionary explanations:

  • suggest that any behaviour/characteristic that promotes survival and reproduction will be naturally selected
  • This is because such behaviours/characteristics are adaptive and are therefore the genes for that behaviour/characteristic will be passed on to subsequent generations
  • E.g. Bowlby said attachment is adaptive because it means an infant is more likely to be protected and therefore more likely to survive
  • This means attachment behaviours are naturally selected 
• Example for nurture - behaviourism:

  • John Locke claimed newborn infants are born a blank slate
  • Behaviourists assume all behaviour can be explained in terms of experience alone
  • Skinner – behaviour learnt through positive/negative reinforcement (we learn about rewards and punishments from our environment)
  • Pavlov – learn through association (between stimuli in our environment)
  • Behaviourists claimed attachment could be explained in terms of classical conditioning (associating mother with food and therefore associating pleasure with mother)
• Example of nurture - SLT:

  • Bandura claimed behaviour is learnt through imitation and vicarious reinforcement. This is nurture based because it focuses on models’ behaviour in our environment.
• Relative importance of heredity and environment in determining behaviour - interactionist approach

  • Heredity (nature) and environment (nurture) interact
  • E.g. attachment patterns between an infant and its parents are often the result of a ‘two-way street’
  • The child’s innate temperament will influence the way its parents respond to it – and their responses will in turn affect the child’s behaviour 
  • Therefore, nature creates nurture
  • For this reason, psychologists are more likely to ask what the relative contribution of nature and nurture is to our behaviour rather than trying to pick one or the other only. 
• Diathesis - stress model:

  • The diathesis-stress model suggests that mental illness is caused by genetic vulnerability – but that this genetic predisposition is only expressed if there is a trigger from the environment
  • E.g. the MAOA low-activity gene may make someone more likely (genetically vulnerable) to be more aggressive than someone who doesn’t have that version of the gene - but they need a traumatic event (environmental trigger) to occur in the first 15 years of their life to trigger the MAOA low-activity gene to actually make them an aggressive person. 
• AO3:

  • One criticism of using only nature or only nurture to explain behaviour is that certain disorders may involve a combination of nature and nurture.
  • An example of this is evident in the disorder PKU (phenylketonuria). This disorder can result in brain damage. 
  • It is an inherited disorder, however if the condition is detected at birth the infant can be given a special diet that prevents the brain damage
  • This suggests that the disorder is not only due to nature as it can be prevented from causing damage through nurture. 
• AO3:

  • criticism of explanations focussing only on nature or nurture is that twin studies never show 100% concordance rates
  • For example, even when MZ twins (who share 100% of their genes) grow up together they do not show perfect concordance rates for many behaviours/disorders
  • This could be because, even though siblings may be raised within the same family, they may not have experienced exactly the same upbringing
  • This supports the view that heredity (nature) and the environment (nurture) cannot be meaningfully separated as they both have an influence on behaviour
• AO3:

  • Support for the idea that genes and environment interact comes from constructivism
  • This suggests that people create their own ‘nurture’ by actively selecting environments that are appropriate for their ‘nature’
  • For example, a naturally aggressive child is likely to feel more comfortable around children who show similar behaviours and will choose their environment accordingly
  • This environment then affects their development – meaning nature and nurture interact to influence a child’s behaviour
• AO3:

  • An argument against the idea that genetics and environment are separate comes from epigenetics
  • Epigenetics refers to the idea that life experiences, such as nutrition or stress, can modify how our genes are expressed
  • These changes in gene expression can then be passed on to our children (the actual DNA sequence doesn’t change just the expression of the gene)
  • This suggests that genetics and environment are much less separate than was previously thought.