The nature-nurture debate

• The Nature vs. Nurture debate examines the extent to which human behaviour, traits, and development are determined by genetic inheritance (nature) or environmental influences (nurture).
• The nativist approach (nature) argues that human characteristics are innate: the result of heredity.

  • belief that genetic and biological factors predominantly shape human behaviour.
• The heritability coefficient is used to assess heredity.

  • It is a numerical figure ranging from 0 to 1 which indicates the extent to which a characteristic has a genetic basis.
  • 1 means a characteristic is entirely genetically determined.
• The general figure for heritability in IQ is around 0.5 across multiple studies in varying populations (Plomin, 1994).

  • This suggests that both genetics and the environment are important factors in intelligence.
• The empiricist approach (nurture) suggests behaviour is learned from the environment through conditioning, but we are born a blank state.
• The interactionist approach argues that nature and nurture interact, rather than operate separately so researchers instead should study how they interact and influence each other.
• The diathesis-stress model is an example of interactionism:

  • Genetic vulnerability (diathesis) interacts with environmental stressors to trigger disorders (e.g., schizophrenia).
• Epigenetics is an example of interactionism:

  • Environmental factors (e.g., stress, diet) can influence gene expression, which can even be passed to future generations.
• The biological explanation of schizophrenia shows support for the nature debate:

  • Genetic Influence: Twin and family studies support a genetic basis.
  • Gottesman (1991) found that the concordance rate for schizophrenia is:
  • 48% in MZ twins (identical)
  • 17% in DZ twins (fraternal)
  • 9% in sibling
• The family dysfunction explanation for schizophrenia supports the nurture debate.

  • Bateson et al. (1956) proposed the Double Bind Theory, where conflicting messages from parents, causes confusion which increases schizophrenia risk.
  • High levels of Expressed Emotion (EE) (e.g., criticism, hostility) in families can lead to relapse.
• The Diathesis-Stress Model supports interactionism. It suggests schizophrenia arises when a genetic predisposition is triggered by environmental factors (e.g., trauma, drug use).

  • Tienari et al. (2004) found that adopted children with a genetic risk for schizophrenia were more likely to develop it only if they were raised in a dysfunctional family environment.
• Bowlby's monotropic theory of attachment supports the nature side of the debate.

  • Infants have an innate tendency to form attachments for survival.
  • Social releasers: babies have innate 'cute' behaviours (e.g. crying, smiling) to trigger caregiving.
  • The critical period (first 2 years) is biologically determined.
• The learning theory (cupboard love) for attachment supports the nurture debate.

  • Attachments are learned through classical conditioning (association between caregiver and food) and operant conditioning (rewarding caregiver presence).
• The interactionist approach to attachment:

  • Attachment is driven by both innate biological mechanisms and environmental influences (caregiver interaction, culture, and social norms).
  • Van IJzendoorn & Kroonenberg (1988) found variations in attachment types across cultures, suggesting attachment styles are shaped by child-rearing practices rather than purely innate mechanisms.
• The genetic explanation for criminal behaviour supports the nature debate.

  • Raine (1993) found that MZ twins had a 52% concordance rate for criminality, compared to 21% in DZ twins, suggesting a genetic influence.
  • Brunner et al. (1993) identified a "warrior gene" (MAOA-L) linked to aggressive behaviour.
• The differential association theory (Sutherland, 1939) supports the nurture debate:

  • People become criminals due to exposure to pro-criminal attitudes from family and peers.
• A weakness is that the interactionist approach may better explain behaviour. The Diathesis-Stress Model explains mental disorders like schizophrenia as a result of a genetic vulnerability (diathesis) combined with environmental stressors (nurture). Tienari et al. (2004) found that adopted children with a genetic predisposition to schizophrenia were more likely to develop the disorder if raised in a dysfunctional family. This suggests that biological and environmental factors interact, rather than one being solely responsible for behaviour. It challenges extreme nativist or empiricist views.
• A strength is that it has practical applications in developing effective treatments for psychological disorders. For example, assuming schizophrenia is entirely due to genetic factors affecting dopamine regulation led to the creation of antipsychotics, which block dopamine receptors as treatment. However, research suggests that CBT alongside medication is more effective than medication alone (Tarrier et al., 2004). This supports interactionism, as by acknowledging both nature and nurture, it can significantly improve patient outcomes. This weakens the debate as it may be too simplistic.
• A limitation is that it is difficult to separate the effects of genetic and environmental influences. Twin studies support nature, as MZ twins have higher concordance rates, but they also share similar environments, making it hard to distinguish between the two. For example, Gottesman’s (1991) schizophrenia study found a 48% concordance rate in MZ twins, but since it is not 100%, this suggests environmental factors must also play a role. This reduces the validity of the debate as it tries to separate nature and nurture, failing to recognise how they interact in real-life.
• An issue is that the debate can lead to determinism, ignoring free will. Nativists support biological determinism, which suggests behaviour is purely genetic, raising ethical concerns, such as justifying discrimination based on genetic predisposition to criminality. Empiricts support environmental determinism, which claims behaviour is entirely shaped by experience, removing personal responsibility. In reality, behaviour results from both genes and environment, making a purely deterministic view of the debate oversimplified.