The historical context and definitions of nature and nurture

The nature-nurture debate is a fundamental discussion in psychology that explores the origins of human behaviour and characteristics. It centres on whether these traits are primarily determined by innate factors or shaped by environmental influences.

Core definitions in the nature-nurture debate

• Nature (genotype) - Refers to innate characteristics that are determined by genetic and physiological factors inherited from birth.
• Nurture - Encompasses the impact of the environment, upbringing, and personal experiences on shaping behaviour and traits.

Historical perspectives on nature and nurture

For centuries, thinkers have argued over the source of human behaviour. In the 18th century, nativists like Jean Rousseau believed all traits were innate, while empiricists like John Locke proposed that individuals are born as a 'blank slate', with the environment shaping their unique characteristics.

Modern perspectives on nature and nurture

Modern psychology largely accepts that both nature and nurture play a role, moving away from an either/or perspective to focus on how they interact to influence behaviour. The debate now centres on the relative contributions of inherited traits versus environmental factors in determining personality and actions.

The interactionist approach and challenges in separating nature and nurture

The interactionist approach posits that nature and nurture are not independent forces but work together to shape an individual's character and behaviour. Disentangling their individual contributions is complex due to their intertwined effects.

Key concepts in the interactionist approach

• Genetic potential and environment:
  • Gottesman (1963) introduced the idea of a reaction range, suggesting that individuals have a genetic potential (genotype) for traits like intelligence or height, but the environment determines the extent to which this potential is realised (phenotype).
  • For instance, a child with high genetic potential for intelligence might not achieve it without access to quality education.
• Diathesis-stress model:
  • This model explains that genetic predispositions (diathesis) for conditions like schizophrenia interact with environmental stressors.
  • A higher genetic vulnerability increases the likelihood of developing the disorder, but this often depends on the level of stress experienced.
• Environmental override:
  • In some cases, environmental factors can override genetic predispositions.
  • For example, phenylketonuria (PKU), a genetic disorder that can lead to brain damage, can be managed by avoiding certain proteins in the diet, preventing the condition from worsening.

Genotype-environment correlations

Genotype-environment correlations highlight how genetic makeup and environment are interconnected, further complicating the separation of nature and nurture.

Plomin et al. (1977) identified three types:

1. Passive correlation - Individuals with similar genes, such as family members, often experience similar environments. For example, siblings might display aggression due to shared genetic tendencies or because their parents create a hostile home environment influenced by their own genetic predispositions.
2. Reactive correlation - Genetically influenced traits can shape how others respond, creating specific environmental experiences. For instance, people often react more positively to those with attractive features, meaning inherited traits partly determine the social environment.
3. Active correlation - Individuals may seek out environments that align with their genetic inclinations, a concept Bandura (1986) termed reciprocal determinism. This means behaviour influences environment just as environment shapes behaviour, such as a naturally curious person seeking intellectually stimulating settings.

Evidence from animal studies

Studies comparing rats raised in barren, dark cages to those in enriched, stimulating environments show that the latter perform better in problem-solving tasks and learn faster. This suggests that environment can significantly influence the expression of innate genetic capabilities.

Research methods for studying nature-nurture influences

Psychologists employ various research methods to investigate the contributions of nature and nurture to behaviour. Each method provides insights but also faces limitations due to the complex interplay of these factors.

Family studies

• These studies examine whether family members share traits more often than unrelated individuals, which could indicate genetic influences.
• For example, Solyom et al. (1974) found that phobias often run in families, suggesting a hereditary component.
• Limitations - Similarities might not be purely genetic; shared environments mean family members could learn behaviours from each other through observation, clouding the distinction between nature and nurture.

Adoption studies

• Adoption studies compare adopted children with their biological and adoptive parents. Greater similarity to adoptive parents suggests nurture's role due to shared environment, while similarity to biological parents points to nature.
• Plomin et al. (1988) found stronger IQ correlations within biological families compared to adoptive ones, indicating genetic influence.
• This method helps isolate environmental and genetic factors by studying individuals raised apart from their biological relatives.

Twin studies

• Twin studies compare identical (monozygotic, MZ) twins, who share 100% of their genes, with non-identical (dizygotic, DZ) twins, who share about 50%.
• Higher concordance rates (likelihood of both twins sharing a trait if one has it) in MZ twins suggest genetic influence.
• Holland et al. (1988) reported a 56% concordance rate for anorexia in MZ twins compared to just 5% in DZ twins, supporting a genetic basis for the disorder.
• Limitations - If a trait were entirely genetic, MZ concordance would be 100%, indicating environmental influence. Additionally, MZ twins are often treated more similarly than DZ twins, which could affect results. Studying twins raised apart offers clearer insights but is harder to conduct.

Psychological approaches and their stance on the nature-nurture debate

Different psychological perspectives adopt varying positions on the nature-nurture debate, reflecting their focus on specific influences over human behaviour and development.

Positions of major psychological approaches

• Psychodynamic approach - Freud's theory integrates both nature and nurture. It highlights innate instincts and drives within the id as natural forces, but also stresses that early experiences can lead to fixations during developmental stages, showing environmental impact.
• Biological approach - This perspective heavily emphasises nature, focusing on genetically determined brain structures and evolutionary influences. Behaviours like aggression are seen as having survival value, though environmental factors can shape brain development and override genetic tendencies.
• Cognitive approach - While acknowledging genetically determined mental processes, this approach accepts environmental influence on their development. Piaget's theory suggests that cognitive growth unfolds through genetic predispositions but requires environmental stimulation to progress.
• Behaviourist approach - Strongly aligned with nurture, behaviourism argues that most behaviours are learned through conditioning, with only basic reflexes and instincts being innate, such as blinking.
• Humanistic approach - Leaning towards nurture, this perspective sees behaviour as driven by a natural desire to achieve full potential (self-actualisation). However, reaching this potential depends heavily on life experiences and environmental conditions.