Are We Born With Our Personality?

A major new study published in Nature has provided some of the strongest evidence yet that personality has a substantial genetic component. Led by Ted Schwaba and an international research team, the study combined genetic and personality data from 46 cohorts involving between roughly 611,000 and 1.14 million people.

The researchers examined the genetics of the Big Five personality traits: extraversion, agreeableness, conscientiousness, neuroticism and openness to experience. They identified 1,260 genetic variants associated with personality, including 824 that had not previously been clearly linked to these traits.

The scale of the study matters because earlier research into personality genetics was often too small to reliably detect the very small effects of individual genetic variants. By bringing together data from more than a million people, the researchers were able to identify a much larger number of associations and test whether those findings held up across different populations and, importantly, within families.

The overall conclusion was clear. Personality is genetically influenced, but it is not genetically simple.

There is no single gene for extraversion, conscientiousness or any of the other broad personality traits. Instead, personality appears to be highly polygenic, with thousands of genetic differences each contributing a tiny effect. The researchers estimated that around 16,000 independently associated common genetic variants may contribute to each of the major personality traits.

The effect of any one of those variants is extremely small. To put that into perspective, the researchers estimated that a typical significant genetic variant associated with extraversion might shift someone from roughly the 50th percentile to about the 50.35th percentile. No individual gene therefore tells us very much about a person, but thousands of such effects acting together can begin to produce measurable differences across a population.

How much of personality is genetic?

The common genetic variants examined in the study explained a modest but measurable proportion of variation in personality scores. Depending on the trait and the method used, they accounted for around 5 to 9 per cent of observed differences, with somewhat higher estimates when the reliability of personality measures was taken into account.

These figures are lower than the heritability estimates traditionally produced by twin and family studies, which have often suggested that around 40 to 60 per cent of variation in personality is associated with genetic differences. This is not especially surprising. Genome-wide association studies are very good at identifying common genetic variants, but they do not capture every form of genetic influence.

The significance of the new study is therefore not that it has finally calculated exactly how much of personality is inherited. It is that it substantially strengthens the evidence that inherited genetic differences make a genuine contribution to personality.

One of the most convincing parts of the study came from comparisons within families. Genetic associations can sometimes be misleading because parents pass on both genes and environments. A parent with a particular genetic disposition may also create a particular type of household, making it difficult to know whether an apparent genetic effect is actually being produced indirectly through family life.

The researchers addressed this by comparing relatives, including siblings and dizygotic twins. The genetic prediction of personality remained remarkably strong. Across the Big Five, the within-family association was around 96 per cent as large as the association found across the wider population.

That makes it much less likely that the genetic findings are simply an indirect reflection of being raised in a particular kind of family environment. There appears to be a genuine inherited contribution to personality.

What are the Big Five?

The study used the Big Five because it is one of the most widely accepted ways of describing broad differences in personality. The five traits are not personality types into which people can be neatly sorted. They are dimensions, and everybody falls somewhere along each of them.

Extraversion broadly describes differences in sociability, activity, stimulation seeking and positive engagement with the environment. People higher in extraversion tend to seek more interaction, stimulation and activity, while people lower in extraversion may prefer quieter environments, smaller groups and lower levels of stimulation.

Agreeableness concerns tendencies towards cooperation, trust, compassion and social harmony. Someone higher in agreeableness may be more inclined towards compromise and concern for others, whereas someone lower in agreeableness may be more sceptical, competitive or willing to challenge others.

Conscientiousness reflects tendencies towards organisation, planning, persistence and behavioural regulation. People higher in conscientiousness are generally more inclined to plan ahead, maintain routines, delay gratification and persist towards longer-term goals. Those lower in conscientiousness may be more spontaneous, less organised or more influenced by immediate rewards.

Neuroticism is a rather dated-sounding term, but in personality psychology it broadly refers to sensitivity to negative emotion and threat. People higher in neuroticism tend to experience more worry, anxiety, emotional reactivity and distress, while those lower in neuroticism tend to be less reactive to threat and recover more readily from emotional disturbance.

Finally, openness to experience concerns curiosity, imagination, interest in ideas and willingness to engage with novelty. People higher in openness tend to be more exploratory and receptive to unfamiliar ideas and experiences, while those lower in openness may prefer familiarity, convention and more concrete ways of understanding the world.

The Big Five is therefore a useful way of describing recurring patterns in how people tend to think, feel and behave. But describing personality is not the same thing as explaining where personality comes from.

That is where the genetics becomes particularly interesting.

We do not inherit a percentile

One of the easiest mistakes to make when interpreting this kind of research is to imagine that people inherit some fixed percentage of a personality trait. We do not inherit “42 per cent extraversion” or “67 per cent neuroticism”. A percentile is simply a statistical description created after researchers measure large numbers of people and compare them with one another.

The person comes first. The score comes afterwards.

What we inherit is the biological architecture that sits underneath the observable personality.

The human brain is not a single unified mechanism. It is better understood as a system of systems. Different neural and emotional systems contribute to threat detection, reward, attachment, motivation, attention, impulse control, social sensitivity, inhibition and emotional regulation. These systems vary between people in their capacity, their sensitivity, how readily they activate, the threshold required to trigger them, how strongly they respond once activated and how quickly they return to baseline.

Genes help provide the blueprint from which these systems develop.

That is very different from saying that genes contain a completed personality.

A person who later appears highly anxious, for example, may have inherited a threat system that activates particularly easily. Another person may have a reward system that responds strongly to novelty, while someone else may have unusually strong behavioural inhibition or require relatively high levels of stimulation before reward systems become strongly engaged.

These underlying differences can contribute to where someone eventually scores on a personality measure, but the score is not itself the thing being inherited. It is an emergent description of how many underlying systems tend to operate together.

Two people can even arrive at similar personality scores through different underlying mechanisms. Two people who both score highly on neuroticism, for example, may not have identical emotional systems. One may detect threat particularly readily, another may experience negative emotion very intensely once activated, and another may simply take much longer to return to baseline after becoming distressed.

The same is true of extraversion. One person may seek social contact because social reward is unusually strong, another because novelty itself is highly rewarding, while another may simply require greater levels of stimulation before feeling fully engaged.

The Big Five describes the pattern we observe. It does not necessarily reveal the mechanisms producing that pattern.

Why children resemble their parents

Children inherit genes from their parents, so it should not surprise us that some of their underlying emotional and behavioural systems may operate in similar ways. A highly threat-sensitive parent may have a child whose threat system is also relatively easy to activate. A strongly novelty-seeking parent may have a child with a similarly responsive reward system, while a highly socially sensitive parent may have a child who is equally attuned to interpersonal consequences.

This resemblance may be strengthened further by assortative homophily.

People do not select partners randomly. We tend to be attracted to people who resemble us in important ways, including temperament, personality, values and ways of responding to the world. Highly sociable people may be more likely to form relationships with other sociable people, cautious people may feel more comfortable with partners who share a similar temperament, and novelty-seeking people may be drawn to others who enjoy stimulation and change.

This matters because a child may therefore inherit from two parents who are already relatively similar in temperament. Both parents may contribute genetic variants that influence the same underlying emotional or behavioural systems in broadly similar directions.

The child is not a copy of either parent, of course. Genetic inheritance is far too complex for that, and every child represents a unique recombination. But assortative partner selection may increase the likelihood that particular temperamental tendencies are strongly represented in the child.

Then life gets involved

Inherited architecture is only the beginning.

From infancy onwards, these systems are repeatedly activated by experience, and biological systems adapt to the environments in which they operate.

A child with a particularly responsive threat system may develop very differently depending on the world around them. In an unpredictable or frightening environment, repeated activation may increase vigilance and make the system even easier to trigger. In a safe and predictable environment, the same underlying sensitivity might develop into excellent awareness of risk, subtle emotional perception and sensitivity to social cues.

A highly responsive reward system may contribute to impulsive behaviour in one environment, but in another it may become attached to sport, creativity, learning or work and produce extraordinary enthusiasm and motivation.

Similarly, a child who is especially sensitive to other people's responses may develop strong empathy and interpersonal skill. Yet repeated rejection, humiliation or criticism could shape the same underlying sensitivity towards anxiety, avoidance or excessive self-monitoring.

The same underlying architecture can therefore contribute to very different outcomes.

This is why the old argument between nature and nurture becomes increasingly unhelpful. The environment does not operate separately from biology; it acts through biological systems. At the same time, those systems influence how the environment is perceived and experienced.

Two children can encounter apparently identical events and experience them very differently. One may barely register criticism, while another experiences it as deeply significant. One may find uncertainty exciting, while another experiences precisely the same uncertainty as threatening. A busy classroom may energise one child and overwhelm another.

The environment is never acting upon a blank person. It is interacting with a nervous system that already has particular sensitivities, capacities and activation thresholds.

As children grow, the relationship becomes even more reciprocal because people increasingly select their own environments. Sociable people seek other people, novelty-seeking individuals seek stimulation, cautious people avoid uncertainty, conscientious people tend to create structure and intellectually curious people seek out complexity and new ideas.

Those choices create new experiences, which then feed back into the same biological systems that helped generate the choices in the first place. Personality development is therefore not a straight line from genes to behaviour. It is a continuing feedback process in which inherited systems influence experience and experience in turn reshapes those systems.

The capacity for adaptation

None of these biological systems are fixed.

The brain remains capable of adaptation throughout development. Experience can alter response thresholds, learning can strengthen inhibition and regulation, relationships can change expectations about threat and safety, and repeated behaviour can establish entirely new patterns of response.

People also learn to compensate for their vulnerabilities. Someone who finds spontaneous organisation difficult may construct highly structured routines. A naturally anxious person may become exceptionally good at planning and preparation. Someone with a powerful reward response may learn to channel that sensitivity towards sport, work, creativity or another demanding pursuit.

Inherited architecture therefore creates tendencies and possibilities rather than predetermined outcomes.

What the study really tells us

The Nature study does not show that a finished personality is written into DNA before birth. What it shows is that broad personality differences are associated with very large numbers of inherited genetic differences, and that these associations remain strong even when people within the same family are compared.

That is important evidence that biology contributes to personality.

But what we appear to inherit is not the final personality trait itself. We inherit part of the architecture of the systems from which personality emerges. Those systems have different sensitivities, capacities, activation thresholds, response intensities and recovery rates. They interact with one another, with experience and with the environments we increasingly choose for ourselves.

Over time, relatively stable patterns of feeling, thinking and behaviour emerge from those interactions. We call those patterns personality.

The Big Five gives us a useful way of describing them, but the person is not the score and the score is not the biology.

Genes provide part of the blueprint. Experience acts upon it. Learning modifies it. Relationships shape it and adaptation continues throughout life.

What finally emerges is not a percentile inherited from our parents, but a unique human being.