Is Personality Inherited? This is how genes affect personality.

To what extent does the personality of parents passed down to children?

Personality of parents passed down to children?

We have all heard expressions like "he has his father's bad temper", "he is as nice as his mother", "his grandfather was also naughty as a child" and so on.

Since it seems that our way of being is something that runs in the family, to what extent is personality inherited? What is more important when it comes to defining it: genes or environment?

Genetics and behavior, what's the relationship?

As with most animals, human beings inherit DNA from their parents, half of which is made up of the mother's DNA and half of which is made up of the father's. This genetic inheritance influences various aspects, including our behavior, character and values. Nevertheless, and this is the point that differentiates us from animals, is that we are able to set goals and have aspirations, which can be promoted by the environment, family and culture that we live.

Another difference that differentiates humans from other animals is that humans are aware of their genetic heritage, that is, to what extent they are similar to their parents, both psychologically and physically, and, by resorting to free will, humans can try to move away from what is supposed to be in our genes. This is the field of study of behavioural genetics.

Although it is known that behavioural aspects, both those that are adaptive and those that involve psychopathology, are to a greater or lesser extent inheritable, a mistaken belief before the development of the Human Genome Project was that each behaviour or aspect of personality and intelligence would be delimited by one or a small group of genes. However, research discovered that no single gene existed for, for example, schizophrenia, intellectual giftedness, or extraversion.

Each of these aspects, and practically all human behaviour, depends on the interaction of several genes, which can be thousands. Each gene has a tiny impact on personality, but together they shape it and make it similar to that of the parents.

Genes versus environment: who will win?

The influence of genes and environmental factors on an individual's behavior is highly variable throughout life. It has been seen that families, which are themselves an environmental factor, have a major influence on a child's cognitive abilities during early childhood. However, when these children have grown up and are old enough to attend primary school, it seems that the genes take over, blocking the influences of the environment.

Obviously, the claim that the behaviour of six-year-olds can be explained by heredity factors alone, without the environmental influence is false. Education in school, together with contact with other children and the experience of events, benign or unfavourable, shape their way of being and their knowledge, however, it is in these years that their genetic code seems to be more relevant when it comes to determining their personality.

In fact, between the ages of three and six, children try to find an environment that suits them, that is, they select friendships according to their way of being, they try to create an environment that is in line with their predispositions. For example, a child with a tendency to be more active is likely to be interested in sport, which will motivate him/her to play football in the school yard and have contact with other children who enjoy this activity.

Is personality inherited?

The approach to the heritability of personality has been carried out through the best methods that behavioural geneticists have to offer: twin studies, both with monozygotic or genetically identical twins, and with dizygotic, not identical twins. These experiments are ideal, especially when identical twins have been separated at birth. Those traits they share, despite having been raised in different homes, will be attributed to genetic factors.

Although this type of research still has some methodological problems, there are certain patterns in the results. The most powerful personality model at present is McCrae and Costa's Big Five, in which personality is defined based on five major dimensions: extraversion, friendliness, neuroticism, openness to experience and responsibility.

Studies that have researched the personality of twins, both identical and fraternal, indicate that there is a high heritability of personality traits, especially being monozygotic twins. This means that if, for example, an identical twin is cordial, the other twin, with a high degree of security, is also cordial. This is a clear indication that personality is strongly influenced by genetic inheritance.

To what extent does genetics influence personality?

When we talk about something being encoded in genes and being the product of heredity, we are talking about the concept of heritability of a certain trait. Heritability indicates what percentage of variation in the traits of two individuals is due to genetic causes. A high percentage of heritability indicates that the variation of a trait is dependent on genes, while low heritability comes to say that the environmental factors have greater importance.

Research indicates that the heritability of personality traits is around 40%-50%. This means that about half of the variation in personality can be attributed to a genetic component. This should not be misunderstood, as it does not mean that half of an individual's personality is due to genetic factors. Non-shared environmental factors would explain about 30% of the variation, and shared factors would explain 20%.

What should be clear from the concept of personality heritability is that it does not indicate that we have about a 50% chance of inheriting the personality from our parents, or that we will share 50% of that personality. The fact of heritability indicates that, for example, if one person is creative and another is less so, most of that difference is due to genetics and, to a lesser extent, is due to having received influences from the environment, both shared and not shared.

Heritability should not be confused with the idea of genetic determination. The latter refers to the fact that genes can determine a particular trait.

References:

Vukasović, T., & Bratko, D. (2015). Heritability of personality: A meta-analysis of behavior genetic studies. Psychological Bulletin, 141(4), 769-785.

Jang, K., Livesley, W.J., & Vernon, P.A. (1996). Heritability of the big five personality dimensions and their facets: a twin study. Journal of personality, 64 3, 577-91.

Costa, P.T., & McCrae, R.R. (1992). NEO PI-R professional manual. Odessa, FL: Psychological Assessment Resources.