“Do you think that genes influence your personality?”
At first you might think that I’m asking you a stupid question. After all, nearly all our lay beliefs about the world include beliefs that some of our genetic material influences who we become as people. And though we do believe, to varying degrees, that our experiences shape who we are, I’m sure we can’t think of all that many people who believe, like Aristotle, that we are a tabula rasa (a blank slate). Additionally, if you believe in evolution then this implies belief that genes influence who we are. If evolution has taught us anything, it is that survival means passing on the fittest of our genes to the next generation.
However the most recent research in behavioural genetics suggests that this may not be the case.
Genes and Personality: The Early Years
When examining the early years to establish any links between genes and personality, it was typical to examine self-reports of personality and compare these self-reports between fraternal twins (who share roughly 50% of their genes) to those of identical twins (who share 100% of their genes). In these early twin studies, very consistent effects emerged that clearly suggested that when it comes to personality, genes matter.
Researchers calculated heritability estimates – in lay terms, the amount of variation in personality that is explained by genes – by examining personality similarity between twin pairs. For identical twins, heritability estimates hovered around 46%, and 23% for fraternal twins (a heritability of 100% means that all variance is genetic; Jang et al., 1996). Together, this early work was very clear in its suggestion that there are some genetic influences on personality. The next question, was of course, which genes would be the biggest players in the gene-to-personality pathways?
The early work in twins suggests the possibility that eventually, with enough knowledge about human DNA, scientists will be able to discover a specific gene for anything related to personality, preferences, intelligence, or physical characteristics. That’s a potentially exciting domain of future research, and one that researchers have examined very vigorously in the last 15 years or so. In this work (sometimes called “a gene for…“) researchers looked for specific small repeating sections of genes (single nucleotide polymorphisms or SNPs) that identified a version of a specific gene. The SNPs usually were related to the specific production or reception of neuropeptides implicated in any number of social behaviours in non-humans.
One really famous SNP is the APOE4 genetic polymorphism, which has been linked to increased risk for Alzheimer’s Disease in humans.
The critical point in these “a gene for…” studies is that, if we know what parts of personality that a specific neuropeptide influences, then its genetic variants should predict behaviour in a similar fashion.
In the subsequent “gene for…” research, many researchers were left disapointed. Specifically, for every breakthrough finding linking a specific SNP to a personality characteristic, there was a null replication. Several of the most promising candidate genes, such as the MAOA gene which has been linked to antisocial behaviour in past research (Caspi et al., 2002), have failed to replicate in subsequent work, according to several meta-analyses (De Moor et al., 2010).
So, then genes don’t influence personality?
The current prevailing genetic evidence seems to suggest that we actually don’t have genes for personality. And this conclusion doesn’t come from a lack of trying: The US government has spent billions on genetic research.
Of course, the conclusion that genes don’t influence personality is most certainly wrong, after all, we have decades of twin research showing similarity in personality between identical twins. At least some of that similarity has to be genetic. Are we missing something that might help uncover the great mystery linking genes and personality?
Take a longer look at the genes.
One potentially promising approach involves examining many candidate genes that relate to a specific biological system associated with personality. In one such approach, Jamie Derringer led a consortium of researchers in an examination of a collection of SNPs associated with Dopamine in prior research, and then examined associations between this collection of SNPs and sensation seeking behaviour. Sensation seeking is a personality trait that is linked to a number of behavioural disorders relating to substance use and addiction -and much of the human and non-human research indicates that dopamine plays a role in this behaviour.
This work differs from the “gene for..” research of the past because it doesn’t rely on the association of a single SNP related to dopamine influencing sensation seeking. Rather, the study looks at a number of SNPs related to dopamine in prior research, to determine if these SNPs work in concert to influence dopamine levels, and sensation seeking more broadly. This approach is appealing because it involves conceiving of genes and personality not as simple one-to-one relationships, but instead, as complex systems of genes that work in concert to express a personality trait.
The findings of this research were promising: Taking into account all the SNPs associated with sensation-seeking behaviours as an aggregate, dopamine genes worked in concert to explain around 6.6% of variation in sensation-seeking behaviour (Derringer et al., 2010).
Current Trends in Research.
Current research has gone back to basics to try to explain the link between genetics and personality. As your high school biology teacher told you, DNA is a code for building proteins, hormones, and neuropeptides that serve specific cellular functions within the body. One thing that early gene-personality work overlooked is that a lot has to happen to allow DNA to code for specific hormones/neuropeptides, that then have to act at the cellular level to subsequently influence personality. In short, genes need to be expressed at a cellular level in order to influence personality.
So current research seems to suggest that while the “a gene for…” theory has been debunked, there is strong evidence to suggest that a number of genes working in concert can affect behaviour(s) so long as they are at least expressed at a cellular level.
Source: Horton, R. (2014) Omega Support Services
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Please follow the instructions below, being careful not to answer too many questions before instructed to.
Before completing the exercises go through the article and check the meaning of any new vocabulary with a dictionary if necessary.
1. How would you define personality?
2. Concerning your personality, which parent do you take after the most.?
3. Think about your answer to Question 2 above. How do you explain it? What are your views on where a person’s personality comes from?
4. Does a personality change? In what ways and for what reasons?
5. What factor(s) can cause sudden dramatic changes in personality?
Read the first section only before answering the following questions.
6. What opinion are people expected to believe concerning the development of personality?
7. Do you think this article will support this idea or not? Explain your thinking.
1. What does the author mean by a tabula rasa or blank state?
2. Why are twins used to help further understand the role of genetics on personality?
3. How much inheritability is there between both identical and fraternal twins and what initial conclusions do researchers draw from this?
4. What do scientists believe that the understanding of human DNA will help them discover?
5. What is the “a gene for…” theory and why is it largely rejected by researchers?
6. The author states ‘Of course, the conclusion that genes don’t influence personality is most certainly wrong. How does he explain this belief after rejecting “a gene for…” thinking?
7. On what principle does current research focus on and how is it different to “a gene for…” thinking?
8. What does ‘in concert’ mean in the context it is used in?
9. What does the author mean when he says a gene must be expressed?
10. Does the author believe genes affect personality according to the article? Is your answer different to your answer to Pre-Reading Question 5? If so why?
1. Do you agree with the author’s point of view?
2. Will understanding our DNA lead to a scientific understanding of our ‘personality, preferences, intelligence, and physical characteristics’ or are there other factors. If there are what are they?
3. Nature or Nurture – which has the greater influence on personality? Explain your answer. As an option answer this question as an essay (200 words)
* You need to prepare these questions for conversation during your next online / face-to-face session with your tutor.