Nature vs. Nurture

260519 Nature vs Nurture.2

One of the seminal questions in psychology is the balance between Nature verrsus Nurture in determining our personalities

In the 2 May 2026 edition of Nature Laurie Clarke summarise the current industry position in his psper How much of our personalities are determined at birth?

Summary (My disagreements are highlighted in bold.)

The long-running debate over whether personality is shaped more by nature (genetics) or nurture (environment) has become far more complex as modern research advances. While earlier studies suggested that specific genes could strongly influence behaviour, scientists now understand that personality results from the interaction of thousands of genetic factors and countless environmental experiences.

The paper opens with the case of Abdelmalek Bayout, whose prison sentence was reduced after his lawyer argued that he possessed a variant of the MAOA gene, popularly dubbed the “warrior gene”, which had been linked to aggressive behaviour. Although this case reflected early enthusiasm for finding single genes responsible for behaviour, researchers now reject such simplistic explanations. Instead, they recognise that complex traits such as personality are influenced by many genes, each contributing only a tiny effect.

Twin studies have long been central to understanding personality. By comparing identical twins, who share all of their DNA, with fraternal twins, who share about half, researchers estimate that genetics accounts for roughly 40–50% of differences in personality. These studies focus on the “Big Five” personality traits: openness, conscientiousness, extraversion, agreeableness and neuroticism. However, even identical twins often develop noticeably different personalities, highlighting the importance of environmental influences.

Advances in genome-wide association studies have revealed why identifying the genetic basis of personality has proved difficult. Human traits are highly polygenic, meaning thousands of genetic variants each make very small contributions. Current genetic studies explain only around 9–18% of personality variation, far less than twin studies suggest. This discrepancy, known as the “missing heritability” problem, remains unresolved. Scientists believe larger and more diverse genetic databases will help uncover more of the hidden genetic influences.

Environmental influences are equally complex. Contrary to popular belief, major life events such as trauma, marriage or winning the lottery generally have only modest effects on personality. Childhood experiences, particularly severe adversity or abuse, can have lasting impacts, increasing the likelihood of traits such as neuroticism and poorer mental health. However, traumatic experiences in adulthood appear to have surprisingly limited effects on long-term personality.

Researchers also investigate influences before birth. Studies suggest that maternal stress during pregnancy may affect infant temperament, possibly through epigenetic mechanisms that alter gene expression without changing DNA itself. Nevertheless, no single environmental factor determines personality. Instead, personality is considered “poly-environmental”, emerging from the cumulative influence of many small experiences over time.

Genes and environments also interact. Genetic predispositions do not guarantee particular behaviours because environmental conditions can activate, suppress or modify genetic tendencies. As a result, people with similar genetic profiles may develop differently depending on their life experiences.

Recent large-scale genetic studies involving hundreds of thousands of participants have begun identifying genes associated with personality traits. Some findings link genes involved in the body’s stress response, such as CRHR1, with neuroticism, while other research suggests that the prefrontal cortex plays a key role in several personality traits. However, these discoveries remain preliminary, and many biological mechanisms are still poorly understood.

Overall, the paper concludes that neither genes nor environment alone determine who we become. Personality emerges from a highly complex interplay between countless genetic variations and a lifetime of experiences. Rather than being fixed at birth or shaped by a few defining events, personality remains flexible and influenced by an intricate combination of biology and environment throughout life.

I consider a major weakness of this paper is that if fails to define and use temperament.  Temperament in psychology refers to the innate, biologically-based emotional and behavioural traits that appear in early infancy.  Clarke mentions temperament 4 times in his paper but never has a discussion about it.

If you can develop a model of temperament that has a biological basis and is practical, easy-to-learn and use, you will have a very powerful tool at your disposal.  I have help to develop what I consider the best: the 7MTF.  Short for the Seven Motivational Temperament Factors.  This link https://www.emotionalintelligencecourse.com/eq-components/  will provide a quick introduction.