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The Nature-Nurture Debate
Nature-Nurture:
One of the longest lasting and most important debates in psychology. Today, we may refer to it as genetic or inherited influences vs environmental influences
The central question is the extent to which our behaviour is determined by either our genes or the environment. The extreme position would be that behaviour is entirely determined either by genes or environment
However, most behaviours reflect a combination of the two
Approaches:
Different approaches place different emphasis on nature-nuture
The biological approach tends to emphasise genetics rather than environment
Behaviourists assume all behaviour is caused by learning (environment)
The psychodynamic theory assumes that innate or inherited drivers are modified by early experience, so it represents an interaction of genes and environment
Key Words:
Environment: Everything that is outside our body, including people, events and the physical world. Any influence on behaviour which is non-genetic
Lerneer identified different ‘levels’ of the environment, which ranged from pre-natal experiences (e.g. the mother’s physiological and psychological state during pregnancy) to post natal experiences (e.g. the socio-historical context within which the child grew up in). The view that the mind is a ‘blank slate upon which experience writes upon’ is typical of an empiricist/behaviour approach, e.g. John Locke
Nature: Any influence on genetic behaviour, e.g., the action of genes, neurochemistry, neurotransmitter and neurological structures
Heredity: The process by which traits are passed from parents to their offspring, usually referring to genetic inheritance
The heritability coefficient can be used to quantify the extent to which a characteristic has a genetic basis. For example, intelligence appears to have a heritability coefficient of 0.5 (Plomin et al. 1964), so the influences of nature and nurture are equal
Interactionist approach: With reference to the nature-nuture debate, this is the view that the processes of nature and nuture debate, this is the view that the processes of nature and nurture work together rather than in opposition. They are linked in such a way that it does not make sense to separate the influences of the two
Nature:
The nature position is deterministic; it suggests that our genetic inheritance determines the way we are
Genes control every aspect of our behaviour in the same way that they control our physical being; for example, eye colour
Examples:
Genetic explanations:
The more closely related two individuals are, the more likely that they will develop the same behaviour
The concordance rate for a mental disorder such as schizophrenia is 40% for MZ twins and 7% for DZ twins
This illustrates how nature plays a part in contributing to the disorder. However, concordance rates for MZ twins are not 100%, despite being genetically identical
This suggests how nature and the environment also play a significant role in development
Evolutionary explanations:
These are based on the principle that a behaviour which promotes survival will be naturally selected, e.g. running away from fire or avoiding deep water
This is because such behaviours are adaptive, so the individual is more likely to be protected due to displaying social releases (innate, ‘cute’ behaviours which activate the adult mammalian attachment system) and features of infant-caregiver interactions (such as interactional synchrony and reciprocity)
As such, the infant would be more likely to survive and reproduce as an adults
Nurture:
This refers to the importance of the characteristics that we learn from the environment
One approach that is entirely about nurture is behaviourism. This suggests all behaviours are entirely shaped by the activities that occur in the environment
Examples:
Behaviourism:
Behaviorists assume that all behaviour can be explained in terms of experience alone
Skinner used the concepts of classical and operant conditioning to explain learning and suggested that attachment could be explained in terms of classical conditioning where the food reduces the discomfort of hunger (negative reinforcement) and is, therefore, rewarding
Social learning theory:
Bandura proposed that behaviour is acquired indirectly through operant and classical conditioning but also directly through vicarious reinforcement
He acknowledged that biology had a role to play, e.g. the urge to act aggressively could be biological, but the way a person learns to express anger is through environmental influences (such as through observing and imitating the methods of expression of anger displayed by the identified role models)
Other explanations:
The double blind theory of schizophrenia (Bateson et al. 1956) suggests that schiziophrenia develops in children who frequently receive contradictory messages from parents, and these conflicting messages prevent the child from developing an internally consistent construction of reality. This is because when the child behaves incorectly, they are punished by a withdrawal of love from their parents, leading them to believe that the world is dangerous (reflected in paranoid delusions) and confusing (reflected in disorganised thinking)
David Reimer:
David Reimer: David’s penis was accidently burnt of during surgery
Dr Money, a psychologist who was developing a theory of gender neutrality. His theory claimed that a child would take the gender identity he or she was raised with rather than the gender identity corresponding to the biological sex
David’s parents brought him up as a girl, and Money wrote extensively about this case, claiming it supported his theory. However, Brenda, as he was named, was suffering from severe psychological and emotional difficulties and in her teens, when she found out what had happened, she reverted back to being a boy
This case study supports the influence of testosterone on gender development as it shows that David’s brain development was influenced by the presence of this hormone and its effects on gender identity was stronger that the influence of social factor
Evaluation:
The nature-nurture debate is often presented as one which we expect to be able to answer
However, it is likely that most behaviours are the result of some innate elements that are refined as a consequence of an interaction with the environment
In a modern context, these divisions are less obvious, and most researchers now recognise that the most likely explanation of behaviour will include both nature and nurture
The ineractionist approach:
This is the idea that most modern psychologists hold. It is the idea that behaviour is influenced by both nature and nuture
The interactions approach is best illustrated by the genetic disorder PKU (phenylketonuria). PKU is caused by the inheritance of two recessive genes, one from each parent. People with PKU are unable to break down the amino acid phenylketonuria, which builds up in the blood and brain, causing mental retardation. However, if the child is diagnosed early, they are placed on a low protein diet for the first 12 years, which helps to avert this potentially lifelong disorder. Therefore, the disorder PKU (nature) is not expressed because of an altered environment (low protein diet- nurture)
Schizohphrenia: Diathesis stress model:
The diathesis is the biological vulnerability such as being born with a gene that predisposes you to develop a disorder, e.g. single gene PPP3CC. However, the disorder will only develop if there is an environmental ‘stressor’ to trigger it, e.g. dysfunctional family. However, the newer diathesis model suggests that SZ is polygenic, and it is not just family that can trigger SZ, it may be the influence of drugs, e.g. weed. It can be argued that abuse or neglect may not be a stressor (nurture) but may be a predisposition (nature)
Tienari et al (2004):
This has also been illustrated by Tienari et al. (2004,) who studied 145 Finnish adoptees whose mothers had schizophrenia and were then matched with a sample of 158 adoptees without this genetic risk
The two groups were independently assessed after 12 years, and of the total 303, 14 developed schizophrenia, and 11 of these were from the high-risk group
Children without a genetic risk but raised in a family climate characterised by tension and a lack of empathy did not develop SZ
However, children with a genetic risk who experienced the same family climate did go on the develop SZ. This illustrates how being raised in a ‘healthy adoptive family’ has a protective effect
Nurture affects nature:
Maguire et al study of London taxi drivers showed that the region of their brains with spatial memory was bigger than in controls; this is because the hippocampi had responded this way
Maguire et al. studied the brains of London taxi drivers and found a larger grey matter volume in the mid-posterior hippocampus, an area of the brain associated with spatial awareness (skills needed for taxi drivers when they are learning and completing ‘the knowledge’ exam)
There was a positive correlation between increasingly pronounced changes and an increasing length of time that individuals had been taxi drivers. This demonstrates the interaction nature of empiricism and nativism and gives further reason as to why the influences of the two cannot be separated
Epigenetics:
Refers to the material in each cell that acts like a switch to turn on or off, e.g. DNA methylation and histone tail modification. Life experiences control these switches, and these switches are passed on when the DNA is replicated semiconservatively
This is why MZ twins may differ in weight even though they were given the same diets, due to differences in upbringing/experiences causing differences in the individual expression of genes
For example, Caspi et al. (2002) assessed antisocial behaviour in 1000 participants between birth and the age of 26. The researchers found that 12% of men with less MAOA gene expression had experienced maltreatment when they were babies but were responsible for 44% of crimes
This brings a third element into the nature-nurture debate: The experiences of previous generations
Constructionivism:
Plomin suggested that an individual’s ‘nature’ would determine their ‘nurture’ through niche-picking or niche-building
For example, a naturally aggressive child would be more likely to play with and befriend other aggressive children
This in turn would increase the aggressiveness of the child
Therefore, the idea of constructionism further emphasises the multi-layered relationship between nature and nurture
The interactions approach states that nature and nurture interact to form a person’s character:
Gottesman (1963) suggested that people have a reaction range. This means everyone has a certain genetic potential for things like intelligence and height — the genotype.
The environment determines how much this potential is fulfilled (how people turn out) - the phenotype.
For example, someone with a high genetic potential for intelligence, who didn't go to school, may have the same IQ as someone with low genetic potential for intelligence, who received a good education.
The diathesis-stress model suggests that people have genetic predispositions for disorders like schizophrenia.
A person with a higher diathesis (vulnerability) is more likely to develop the trait, but whether they do depends on the amount of stress they experience (i.e. the environment).
One influence can sometimes override another. For example, phenylketonuria (PKU) is a genetic metabolic disorder that can cause brain damage.
But if the person doesn't eat particular proteins, then the disorder won't get worse. This shows how environment can override a genetic disposition.
Determining how far nature or nurture control characteristics can be complicated by genotype-environment correlations — correlations between a person's genes and their environment.
Plomin et al. (1977) identified three types of genotype-environment correlations:
Passive - people with similar genes (e.g. members of the same family) are likely to experience similar environments. For example, two siblings may be aggressive because they have both inherited aggressive tendencies from their parents or because their parents' predisposition towards aggression means that they provide a hostile home environment.
Reactive - genetically determined characteristics may shape a person's experiences. For example, people react more positively towards attractive people, so the kind of environment a person experiences depends partly on their inherited characteristics.
Active - people with particular inherited tendencies might seek out certain environments, which will then shape their behaviour just as their genetic background does. Bandura (1986) called this reciprocal determinism - environment determines behaviour and behaviour determines environment.
Nature-nurture influences can be studied using different methods:
Family Studies:
If family members share a trait more frequently than unrelated people do, then this could imply a genetic influence for that behaviour.
For example, Solyom et al. (1974) showed that phobias can run in families.However, similarities between family members may actually be the result of their shared environment
relatives might learn the behaviour from each other through observational learning.
Adoption Studies:
These compare an adopted child with their biological and adoptive parents. If the child has more similarity with its adoptive parents, then this would imply that nurture is important, because they share the same environment.
Similarity with the biological parents suggests that nature is more important. Plomin et al (1988) showed a stronger correlation of IQ within biological families than adopted families.
Twin Studies:
Identical (MZ) twins share 100% of their genes. Non-identical (DZ) twins share about 50% of their genes. So, if MZ twins are more likely to share a characteristic than DZ twins, it implies a genetic influence. This is shown by concordance rates — concordance means how likely it is that both people in a pair will have a certain characteristic, given that one of them does. For example, Holland et al. (1988) found a 56% MZ concordance for anorexia (i.e. in MZ twins, if one twin had anorexia, then 56% of the time, both twins did), compared to 5% DZ concordance. Which suggests that genes influence the development of anorexia.
However, if a trait was completely genetic, then MZ concordance would be 100%, so their behaviour must also be influenced by environment. For example, people might treat MZ twins more similarly than DZ twins. As such, it's more useful (but also more difficult) to do research on twins who haven't been brought up together.
Different psychological approaches fall on different sides of the debate:
Psychodynamic - Freud argued that personalities are the result of an interaction of nature and nurture. He emphasised the importance of inborn instincts and drives (represented in the id). However, he also said that experiences can result in fixations in the stages of development.
Biological - emphasises genetically determined brain structures and processes. Evolutionary psychology states that many behaviours, e.g. aggression, are genetically influenced because they have survival value. However, the environment influences brain development, so learning can override genetic predispositions.
Cognitive studies genetically determined mental processes but accept that the environment influences their development and functioning. Piaget's theory of cognitive development argues that environmental stimulation is needed for the genetically determined process of development to unfold.
Behaviourist — all behaviours are learnt through conditioning, apart from inborn reflexes and instincts (e.g. blinking). This approach falls most heavily on the nurture side of the debate.
Humanistic behaviour is part of a natural need to reach your full potential. However, whether you reach it depends on your experiences in the world, so the humanistic approach falls more towards the nurture side of the debate.