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- We will kick off our learning by giving an overview of the genetic basis of behaviour psychology.
- Then we will delve into the four methods of behavioural genetics research commonly used.
- After the genetic basis of behaviour in animals will be discussed.
- We will then learn to see if the genetic basis of behaviour can be applied to a specific behaviour, i.e. the genetic basis of prosocial behaviour,
- And finally, we will take a look at some genetic behaviour examples.
Genetic Basis of Behaviour Psychology
The genetic basis of behaviour in psychology explores if human and animal behaviour can be explained by genetics. This area of study is known as behavioural genetics.
Behavioural genetics generally refers to researching and discussing which genes may affect behaviour and to what extent they do so.
The genetic basis of behaviour in psychology investigates how our DNA influences our thinking, behaviours and acts. Our DNA is inherited from our parents, and our behaviour is influenced by the genes that we inherit. The role of our genes in determining our behaviour has been investigated via twin studies, adoption studies, and DNA testing.
Importance of Investigating the Genetic Basis of Behaviour
Psychologists need to investigate the genetic basis of behaviour for various reasons. Firstly, suppose psychologists understand the link between genetics and mental health issues. In that case, they may be able to identify more effective treatments or environments and situations which exacerbate problems in those with genetic predispositions to develop mental health issues.
This could lead to more detailed and effective treatment plans for those with a family history of issues such as depression.
And behavioural genetics may also help us to get a better understanding of people. For instance, it could help us to understand crime and identify those who may be more likely to commit it.
Suppose someone has a dysfunctional MAOA gene and is placed in an adverse environment, such as an abusive upbringing. In that case, we may be able to use this information to tailor and improve social work for those who need it the most, which may result in decreasing criminality rates.
Four Methods of Behavioural Genetic Research
There are four methods of behavioural genetic research that are often used: family studies, twin studies, adoption studies, and molecular genetics.
Genetic Basis of Behaviour: Molecular Genetics
We know that there is a genetic basis of behaviour. But to what extent? Molecular genetics help us identify specifically what genes may be responsible for certain behaviours. Researchers can identify commonalities in individuals with similar traits and behaviours through DNA testing.
The Human Genome Project was a significant feat in behavioural genetic research. After this project in 2003, we finally have a complete map of the human DNA genome; this was a huge leap towards identifying the specific genes that may be responsible for human behaviour and traits.
However, this is no perfect science since several genes and gene combinations could be responsible for just one behavioural trait.
Molecular genetics research has also helped us better understand the gene-environment interaction and the role of epigenetics on behaviour.
Epigenetics is the study of how environmental factors affect gene expression.
A common model proposed to explain the genetic basis of behaviour is the diathesis-stress model.
The diathesis-stress model states that people have a genetic predisposition for neurodivergent behaviour. If they are exposed to certain and sufficient environmental factors, this triggers the development of "atypical" behaviour.
Genetic Basis of Behaviour: Family Studies
Biological families are more likely to have genetic similarities than non-biological families or between families. If a genetic trait or behaviour seems to be common within a family, there may be a genetic basis for this behaviour.
Psychologists and behavioural geneticists may use these findings to launch additional studies. However, biological families often share environmental factors as well.
Siblings and dizygotic twins only share 50% of their genetic makeup.
Therefore, it may be difficult to distinguish whether environmental or genetic factors are responsible for a particular behaviour.
In this sense, the nature vs nurture debate is enduring -- we are both the culmination of our genes and environment. So when studying the genetic basis of behaviour, researchers need to be aware of potential environmental influences. To sus these out further, researchers often turn to twin and adoption studies.
Genetic Basis of Behaviour: Twin Studies
Psychologists and behavioural geneticists who study the genetic basis of behaviour often rely on twin studies. When conducting twin studies, researchers will focus on monozygotic twins (reared together/apart) and/or dizygotic twins (reared together/apart).
Monozygotic twins: (aka identical twins) occur when two individuals are formed when a single fertilised egg splits in two, meaning they share 100% of their genes.
Dizygotic twins (fraternal twins) occur when two individuals are formed by two separate fertilised eggs, meaning they share only 50% of their genes.
Fig. 1 Monozygotic (identical) twins can teach us a lot about the genetic basis of behaviour.
If monozygotic twins share more similarities than dizygotic twins, the assumption is that there is likely a genetic basis for this behaviour.
Christiansen (1977) conducted a study on monozygotic (100% genetic similarity) and dizygotic (50% genetic similarity) twins.
He found that criminality concordance rates (the likelihood that both twins share an attribute) were higher for the monozygotic twins. The findings suggest that between them, the investigated twins must share some genetic information that predisposes them to commit crimes.
Adoption Studies
Adoption studies are also conducted to rule out the possibility of environmental impact on the results of genetic studies. Adoption studies often look at two scenarios:
Twins reared apart
If twins reared apart show similarities in a behavioural trait, researchers would infer a genetic basis to this behaviour over environmental.
Adopted children have similarities to biological parents vs adoptive parents.
Suppose an adopted child has more similarities to their biological parents than their adoptive parents. In that case, we may be able to assume there is a genetic basis for behaviour and vice versa.
Leonard Heston (1966) researched if adopted children whose biological mothers have schizophrenia would go on to develop it. He found that 10.6% of adopted children went on to develop schizophrenia. This study suggested that there was a genetic component to developing schizophrenia.
Genetic Basis of Behaviour in Animals
In addition to observational and experimental studies, a comparative study is a common method used to study the genetic basis of behaviour in animals.
Comparative studies look at traits from the animal and its ancestors to understand the origin of the behaviour.
Comparative psychology studies animals and their behaviour to see which areas of study and their findings can be applied to humans.
Animal Behaviour Development and Evolution
Animal behaviour is thought to have evolved due to natural selection over generations. Charles Darwin originally coined this idea in his book 'On the origin of species.' Behavioural traits change over generations, much like the physical characteristics of organisms do.
The four principles of evolution are as follows:
Variation: Variation is the naturally occurring differences in physical and behavioural characteristics between individuals of any given species.
Inheritance: Inheritance is when individuals from a species produce offspring who inherit their physical and behavioural characteristics.
Selection: Selection refers to individuals' genetic makeup influencing their ability to survive or produce offspring. Through selection, weaker genes are phased out of the population, and more desirable genes and traits become more common in the population.
Time: The processes of variation, inheritance and selection gradually work to change the species overall. For marked changes to occur, a lot of time is required.
Prey animals such as deer have adopted a cautious nature, which prepares them for dangerous encounters and gives them a better chance to detect and escape danger.
Theoretically, animals that expressed these characteristics to a lesser extent would be killed by predators before mating age or not selected for mating.
Genetic Basis of Prosocial Behaviour
Do we display acts of kindness simply out of the goodness of our hearts, or could there be a genetic basis for prosocial behaviour? As evidenced by several twin studies, many psychologists would argue yes.
Prosocial behaviour: voluntary behaviour that helps or benefits another.
For example, a study by Ando et al. (2003) found that the heritability for cooperativeness is around 47%. Another study by Pederson et al. (2015) found that the heritability to donate blood is around 53%.
So what are some reasons for the genetic basis of prosocial behaviour? It may, in part, be due to our level of empathy or desire to be altruistic. Researchers have found a genetic component to these behaviours.
Prosocial behaviour can also have an evolutionary advantage. Helping out another in trouble which could later help you, can have a major advantage for survival.
These types of alliances could be the difference between life and death.
Fig. 2 Offering a helping hand has a genetic basis for this behaviour.
Genetic Behaviour Examples
Perhaps one of the most well-studied genetic behaviour examples is the MAOA gene, which research suggests is linked to aggression. Some people are born with a defective version of the MAOA gene, MAOA-L, which leads to high levels of aggression, resulting in Brunner syndrome.
Brunner syndrome, initially investigated by Brunner et al. (1993), is a rare genetic disorder caused by a mutation in the MAOA gene, resulting in increased levels of rage and aggression.
In Brunner's study of a large Dutch family, it was found that five of the males, who were exhibiting high levels of aggression, each had the dysfunctional MAOA gene. This resulted in them committing acts of violence, such as threatening people, fighting and attacking people, and even setting fires on properties.
This is an example of genetics affecting behaviour.
A variety of lesser-known genes have also been discovered.
For example, 18 genes have been discovered that can be linked to autism.
Our ability to link genes to behaviour and developmental functions may help us to understand neurodivergence (when someone thinks, acts, or behaves in an "atypical" way).
Human behaviour has changed drastically over the years, from primitive hunter-gatherer tribes to complex societies built on technological advancements. This is a product of evolution and the rapidly changing environments humans find themselves in, contributing to the genetic basis of behaviour.
Some examples of genetic behaviour that have changed over time include language, the prefrontal cortex (resulting in reduced violence), and mating strategies.
Our ability to form complex societies that simultaneously shape and are shaped by human behaviour is also a result of evolution.
Genetic Basis of Behaviour - Key takeaways
- The genetic basis of behaviour psychology refers to researching and discussing which genes may affect behaviour and to what extent they do so.
- Twin studies and adoption studies are common methods of behavioural genetic research.
- In addition to observational and experimental studies, comparative studies are a common method used to study the genetic basis of behaviour in animals.
- Several studies have shown a genetic basis for prosocial behaviour.
- Some genetic behaviour examples include research on the MAOA gene and evolution.
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Frequently Asked Questions about Genetic Basis of Behaviour
How does genetics influence human behaviour?
Some genetics have been found to influence human behaviour; for example, the MAOA gene has been linked to aggression.
Why do psychologists investigate the genetic basis of behaviour?
Psychologists investigate the genetic basis of behaviour to learn more about the origins of human behaviour and ways in which we can measure human behaviour.
Do genetics contribute to behavior?
Genetics contribute to human behaviour, but human behaviour is a combination of genetics and environmental factors.
What is a genetic basis?
A genetic basis is when the foundation of a concept is based on genetics.
What is an example of behavior genetics?
An example of behaviour genetics is research into autism, which attempts to understand the cause by analysing the genetics of individuals with autism and their first-degree relatives.
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