Can our genes explain our interests, personality, intelligence, and the choices we make in life? Should we care about how children are raised or are their outcomes in life already written in their genes?
The nature vs. nurture debate has been around since Ancient Greece when Plato and Aristotle disputed the origins of human behaviour. However, the development of genetics has gained a renewed interest in the scientific community and the eugenics community. Historically, the nature side of the debate has been weaponised to oppress minorities and justify systemic inequalities. We have come a long way since then, but where exactly are we now?
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Fig. 1: The nature and nurture debate has pushed for investigations of the influences that shape who we are.
Nature vs Nurture Debate Definition
The nature vs nurture debate in psychology is concerned with the formation of a person's characteristics and behaviour. Historically, the debate has taken an either-or approach; who we are is either shaped by our genes or our upbringing, it is either natural or it is nurture that shapes who we are.
Let's consider the two extreme viewpoints. The views that stand towards the nature side of this spectrum are called nativists.
The nativist view attributes our behaviour and characteristics to genes and sees them as innate and shaped through evolution.
On the other side of the debate, we have the empiricist view. According to empiricism, we are born a 'tabula rasa' (blank slate), and our minds are shaped by experiences and knowledge as we grow up.
The empiricist view attributes our characteristics to experiences and learning.
Another more balanced position, the interactionist view, places itself in the middle of the two extremes.
The interactionist approach in the nature-nurture debate states that behaviour is shaped by the interaction between nature and nurture.
The two influences work together, mutually influencing each other. The approach also argues that there are different 'levels' of explanation (e.g. biological, cognitive or social) that must be considered when examining a particular behaviour.
Fig. 2: The interactionist view takes both biological and environmental factors into account, as well as their interactions.
Nature vs Nurture Debate Examples
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The biological approach in psychology is often based on the nativist perspective. This approach proposes that our characteristics and patterns of behaviour are innate, they are caused by our genes, which have been passed onto us from our ancestors through the process of evolution. Behaviour and mental characteristics are viewed as hereditary.
One example of a nativist theory in psychology is Chomsky's Universal Grammar theory.
Chomsky claimed that children have an innate ability to understand different language categories, e.g., nouns or adjectives. He claimed that these categorisation abilities allow children to make sense of the grammar of any language. Supporters of this theory claim that language is too complex of an ability to acquire without built-in 'tools' to help us process it.
In psychology, the empiricist perspective is taken by the learning approach to understanding behaviour. The learning approach argues that behaviour actively evolves throughout our lives, either through direct interactions with the environment or by observing others that modelled certain behaviours for us. This view also rejects the possibility of behaviours being innate.
Behaviourism focuses on the impact of the environment on behaviour. It proposes that all behaviour develops through conditioning. Conditioning can occur either through association or reinforcements (rewards and punishment). In a nutshell, the environmental consequences of our behaviour will either weaken or strengthen our behaviours in the future.
The interactionist view in psychology recognises the importance of both biological and environmental correlates of behaviour, personality, and well-being. It is also interested in investigating how our genes can interact with our environment.
The psychodynamic approach, for example, posits that our behaviour is driven by innate instincts but also influenced by our development as well as experiences.
Many biological models of understanding mental health have changed to account for environmental factors as well, giving rise to interactionist models of mental illness.
The diathesis-stress model is an example of the interactionist approach. The model suggests that simply a genetic predisposition ('diathesis') is not enough; an external trigger ('stressor') is required to develop the condition. The model is used to understand the development of schizophrenia.
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Nature vs Nurture Debate Psychology Research
How can we assess the degree to which nature and nurture influence a particular characteristic or behaviour? To understand how much genes contribute to a specific characteristic, we calculate heritability coefficients based on the data collected from family studies.
The heritability coefficient is a statistic which tells us how much variation in a trait can be attributed to genes on a population level. If a trait has high heritability, it means that individuals with similar genes will be more similar to this trait.
So, let's say that creativity is highly heritable, in this case, we would see people with similar genes (e.g. twins or family members) share similar creativity levels. If creativity had low heritability, we would see a broad variation in creativity among twins or family members.
Let's say that 60% of the variation in extraversion in society is accounted for by genes. This does not mean that 60% of your extraversion was accounted for by your genes. Individually, we differ greatly on these estimates.
How is Heritability Assessed?
Heritability estimates can be calculated using data from adoption studies or twin studies, which examine the similarity between individuals with different degrees of genetic relatedness.
- Adoption studies investigate how similar children adopted at birth are to their biological vs. adopted families.
- Twin studies investigate similarities between identical twin pairs that share 100% of their genes and fraternal twin pairs that only share 50% of their genes.
A hypothetical study found that the musical talent of children adopted at birth was predicted by their biological parents' musical abilities, but did not correlate with the musicality of their adopted families. This suggests that musical talent is highly heritable, at least in the population studied.
A hypothetical twin study found that both identical and fraternal twin pairs share similar levels of tolerance for spicy foods. This suggests that tolerance for spicy foods is not highly heritable.
Can Nature Affect Nurture?
It can be difficult to separate nature and nurture influences in research, as genes can influence our behaviour indirectly by affecting our nurture.
Nature can influence nurture through reactive gene-environment interaction, or niche picking.
The behaviour we are genetically predisposed to can influence how others react to us, this way influencing our environment.
If a child has a genetic predisposition to be smart and comes from a wealthy background, they might be given more opportunities to develop from early on in their development. These opportunities can further develop their intellect.
These interactions were described by Plomin et al. (1977), who investigated nature-nurture interaction in family studies. They found this interaction could potentially bias gene-behaviour correlations obtained from family studies.
Further work done by Scarr and McCartney (1983) identified three ways that genes influence our behaviour indirectly, through our environment.
- Passive way – we are provided with an environment by our biological parents.
- Reactive way – the way others react to us can be influenced by our temperament.
- Active way – niche picking, which involves the active selection of our environment.
Niche picking refers to the tendency to seek environments in our life that complement our genetic traits.
People with good musical ears might seek environments where they can learn more about music.
Introverts can be drawn to quiet settings or activities that don't require too many social interactions, while people that have an innate tendency to be aggressive might look for environments where conflict is likely to occur.
Can Nurture Affect Nature?
The genome-environment interaction can also occur in the opposite direction.
Nurture can affect nature through the process of neural plasticity. The environment can also mediate the relationship between genes and behaviour.
One way that our experiences affect our biology is through neuroplasticity. The functioning of our nervous system and the structure of our brain can be affected by our experiences.
Maguire et al. (2003) found that the hippocampi of London taxi drivers were greater than the ones of controls. Hippocampus is a brain structure associated with spatial memory. The authors theorised that learning to navigate the London streets changed the drivers' brain structure.
An example of how the environment can mediate the influence of genes on psychological outcomes is provided by
Turkheimer et al. (2003), studied influences on intelligence in a sample of 7-year-old twins.
They found that the contribution of genes to intelligence in children varied depending on their socioeconomic status.
- IQ of children growing up in impoverished families was mostly attributed to their environment, while genes had a contribution close to zero,
- IQ of children growing up in wealthier families was mostly attributed to their genes, while their environment played a negligible role.
Turkheimer et al. (2003) found that the heritability of IQ in impoverished children was almost zero (0.01), while the in a sample of wealthy children heritability of IQ was very high (0.72).
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Fig. 3: The contribution of genes to intelligence has been found to depend on one's socio-economic status.
Nature vs nurture debate summary
Currently, it is recognised that both nature and nurture contribute to behaviour and that they can influence each other.
The family studies demonstrate that there are aspects of personality and behaviour that are heritable, as shown by heritability coefficients. We also have evidence of the role of nurture in some behaviours and individual traits, as the heritability of psychological traits in family studies is never 100%, indicating the presence of environmental influences.
We recognise that the contribution of each will also differ depending on the trait or behaviour. Moreover, as demonstrated in the above examples, the two influences can interact through reactive gene-environment interactions, niche picking or neuroplasticity.
Strengths and Weaknesses of Nature Nurture Debate
Arguments for either of the three positions in the nature-nurture debate can be made based on empirical evidence supporting each of the positions.
However, taking on either one of the extreme approaches can be reductionistic, as they discard other potentially relevant levels of explanation and the interactions between nature and nurture.
Extreme positions can also be used to support harmful social policies or attitudes.
- Attributing social inequality to nature has been used to justify injustice, discrimination or even genocide, it can also lead to extreme positions in parenting that disregard providing children with adequate nurture and care.
- Not considering the importance of nature and biological differences is also potentially harmful. For example, Applied Behaviour Analysis therapy has been used to forcefully teach autistic children how to behave in a neurotypical way, disregarding the biological differences that make them behave the way they do.
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Nature Vs Nurture Debate - Key takeaways
- The nature vs nurture debate in psychology is concerned with the formation of a person's characteristics and behaviour.
- The nativist view attributes our behaviour and characteristics to genes and sees them as innate and shaped through evolution. The empiricist view attributes our characteristics to experiences and learning.
- To understand how much genes contribute to a specific characteristic, we calculate heritability coefficients based on the data collected from family studies.
- Psychological research demonstrates that nature and nurture can interact and influence each other.
- The limitations of taking on an extreme view in this debate are that they can be considered reductionistic and support harmful social policies or attitudes.
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