Do Your Genes Affect Your Personality?

Introduction

Personality traits, when deeply classified, can give rise to 4000 terms. But are our personalities written in our genes or is it entirely our environmental factors that affect our traits?

Various studies conducted till now show that a personality of an individual is multifactorial - affected by numerous factors - they can genetically inherit it from parents or environmental factors can influence a trait.

Between 1979 and 1999, they studied about 350 twins in the Minnesota Study of Twins Reared Apart. The study included both identical (monozygotic) and non-identical (dizygotic or fraternal)twins. The study observed that heredity passed some of these traits on to them irrespective of where they are raised - whether in the same household or different, while the external environment imparted others. the study also reported that identical twins share about 50% of their traits while non-identical twins share 20% in common.

Image 1 − Comparison of typical zygote development in monozygotic identical and dizygotic twin (Attribution: Trlkly (Original by Wikipedia editor User:ChristinaT3), Identical-fraternal-sperm-egg, CC BY-SA 3.0)

When a trait is genetic, a certain set of genes influence it, called genotype. And, the traits passed on are referred to as phenotype. The central dogma is a process in which the sections of DNA - genes provide the codes to produce proteins.

Change in Personality Traits Over Time

It is common that an introverted person, as they age, gradually develops an interest to hang out with friends. likewise, an extrovert might prefer to stay alone, finding peace. These changes don’t mean that their original personality has changed. But, over time, they have witnessed slight shifts without affecting their true trait.

Robert Plomin, an American psychologist and geneticist, has spent 30 years finishing his research before concluding his findings in his book Blueprint: How DNA makes us who we are. In his book, he asserts that personality traits lie mostly in our DNA and not by any other factors, such as the way we were raised and other environmental conditions. While 50% of the personality traits are obtained genetically, he argues that the other 50% don’t directly point toward environmental factors. Rather, those environmental factors largely unpredictably and randomly affect us, which, again, are governed by our DNA. One particular gene doesn’t cover all our character traits widely. but it’s a combination of many genes acting together contributing in tiny proportions to the way we behave.

Genes’ role in the behaviour

• Twin studies − Identical twins share the same set of genes - 100% of their genes are the same. That’s the reason they study identical twins to better understand how genes play a part in deriving personality traits from parents to children.

• Adoption studies − adoption studies aim to understand the behavioural patterns of children adopted by parents who are not related biologically to them. In this study, they compare the behavioural pattern of the children with those of their biological parents who are not raising them

• Family studies − when a person in the family shares a trait with his/her parent, the unique genotype responsible for such a share in the trait is studied. These studies also help in identifying some diseases that arise genetically and help in uncomplicated diagnosis.

• GWAS − Genome-wide Associated Studies − study groups of people instead of closely related family members. Through this study, experts can identify genotypes that assist certain personality traits prevalent in a group through screening. It also helps in identifying new findings that were not determined previously. By this method, Single Nucleotide Polymorphisms, SNP (or gene variants) that are responsible for a particular trait can be pinpointed.

How is personality influenced by heredity?

During the DNA replication process, all the codes are copied exactly from the original strand. But there are chances that some mistakes/alterations can happen in this DNA replication process, which will result in slight changes in the new DNA. These mutations give rise to new characteristics in the child, also constituting the diversity of the species. When such mutation happens in a sperm or egg cell, the traits are passed on to the children.

Just because genes are responsible for an individual’s personality it doesn’t mean that a criminal’s son will be a criminal. The trait that made the father a criminal might be responsible for the positive utilisation of the same trait in the son. While the trait remains the same, it’s up to the person how they use it to their advantage.

Gene-Environment Correlation

The gene-environment correlation refers to the idea that genes can influence the environment to which children are exposed. while our genes don’t directly involve environmental conditions, our genotypes determine how we react when exposed to certain situations thus defining our perception, behaviour, personality and cognition.

Gene-environment correlation can be grouped into three categories −

• Passive gene-environment correlation − this refers to the relationship between the genotype parents pass on to the child and the environment in which a child is raised. E.g. when a child is raised in a home, conditions such as having a routine and noise-free environment are effort-fully controlled by the parents which will be passed on to the child. This trait of effort fully controlling the environment is thus transmitted to the child as well.

• Evocative gene-environment correlation − as a result of the genetically influenced trait of a child, when he/she receives a certain kind of response from others in the environment, it is referred to as evocative gene-environment correlation. E.g. when others perceive the child as likeable with the way he/she interacts, it is influenced by the genes transmitted from their parents.

• Active gene-environment correlation − refers to the relationship between the genotype of the child and the environment they prefer. For E.g. the personality trait of social interaction plays its part when a child is less socially exposed, he/she is prone to riskier environments in adolescence.

Scientists have presented, a formula to calculate how much influence heritability estimate a gene has on the behaviour of a group of people. the heritability estimate ranges from 0 to 1 - 0, indicating the least effect of genes influencing your behaviour while 1 represents that the genes have a maximum influence on your behaviour.

With age, as you gather experiences, your gene expression and therefore your behaviour tends to change. Sometimes, it’s your genes that impact your behaviour and at times it’s your environment that plays a major role. Depending upon the experiences you gather, the expression of the genes would vary showing a difference in your behaviour.

In the debate whether it’s nature (gene) or nurture (environment), it’s very hard to predict the amount of impact each has on an individual’s behavioural patterns.

FAQs

Qns 1. What is gene-environment correlation?

Ans. The gene-environment correlation refers to the idea that genes can influence the environment to which children are exposed. while our genes don’t directly involve environmental conditions, our genotypes determine how we react when exposed to certain situations thus defining our perception, behaviour, personality and cognition.

Qns 2. What are the types of studies that determine a gene’s role in behaviour?

Ans. Twin studies, Adoption studies, Family studies and GWAS - Genome-wide Associated Studies.

Qns 3. What are the types of gene-environment correlation?

Ans. Gene-environment correlation can be grouped into three categories - Passive gene-environment correlation, Evocative gene-environment correlation and Active gene-environment correlation.

Qns 4. What is heritability estimate?

Ans. Scientists have presented, a formula to calculate how much influence heritability estimate a gene has on the behaviour of a group of people. the heritability estimate ranges from 0 to 1 - 0, indicating the least effect of genes influencing your behaviour while 1 represents that the genes have a maximum influence on your behaviour.

Qns 5. What is mean by genotype and phenotype?

Ans. When a trait is genetic, a certain set of genes influence it, called genotype. And, the traits passed on are referred to as phenotype.