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Nowadays, it is generally believed that genes, while important, typically act as the foundation upon which environmental and situational factors may affect a person's development and actions. Genes may form a base for our behaviour, but do not necessarily control it.
The genetic basis of behaviour 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 have an effect on behaviour, and to what extent they do so.
The genetic basis of behaviour in relation to psychology investigates how our DNA influences how we think, behave and act. 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.
Some genes may influence how people develop or interact with the environment or situations. Perhaps one of the most well-studied examples of this is the MAOA gene, a gene linked to aggression. Some people are born with a defective version of the MAOA gene, MAOA-L. This leads to high levels of aggression.
A rare genetic disorder associated with MAOA mutation is Brunner syndrome. It was originally investigated by Brunner (1993). 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 fire to 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. This is when someone thinks, acts, or behaves in an "atypical" way.
Studies using twins and adopted children are used to shed light on the genetic basis of behaviours.
Christiansen (1977) conducted a study on monozygotic (100% genetic similarity) and dizygotic (50% genetic similarity) twins. He found that criminality concordance rates (rate of which both twins share an attribute) were higher for the monozygotic twins. This suggests that between them, the investigated twins must share some genetic information that predisposes them to commit crimes. This might be, for example, due to an increase in aggression, as we see with the MAOA gene. However, concordance rates were still fairly low, suggesting that the environment also plays a role in behaviour.
Infants twins, flixr.com
Adoption studies are also conducted to attempt to rule out the possibility of environmental impact on the results of genetic studies. For example, a twin study such as Christiansen (1977) might give us an interesting look at how genetics affect behaviour but it doesn't take into account how environment and upbringing may affect the results. If two twins are brought up in the same household, it is likely that this plays a role in their behavioural similarities, making it harder to determine whether studied behaviour is a result of genetics or environment.
A good example of an adoption study is Heston (1966). In this study, Leonard Heston researched if adopted children whose biological mothers have schizophrenia would go on to develop it. He found 10.6% of adopted children went on to develop schizophrenia. This study suggested that there was a genetic component to developing schizophrenia, and the environment could not stop it from developing.
A common model that is proposed to explain behaviour is the diathesis-stress model. This states that people have a genetic predisposition for neurodivergent behaviour and if they are exposed to certain environmental factors this triggers the development of "atypical" behaviour.
There are three main methods of studying behaviour in animals. Let's have a look at them.
Observational studies: observational studies involve pure observation of animal behaviour, with no interference with variables or the environment of the animal(s).
An example of this would be observing the feeding patterns of animals in their natural habitat.
Experimental studies: experimental studies are when a researcher does have control over variables and uses this control to see how the animal responds.
An example of this would be observing how animals respond to a given stimulus or conditioning.
Comparative studies: comparative studies are when traits from the animal and its ancestors are studied in order to understand the origin of the behaviour.
Another area of psychology known as comparative psychology uses the study of animals and their behaviour to see which areas of study and their findings can be applied to humans, due to the evolutionary commonalities between humans and animals such as monkeys and mice.
It is important for psychologists to investigate the genetic basis of behaviour for a variety of reasons. Firstly, if psychologists understand the link between genetics and mental health issues, 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.
A social worker and her client, flixr.com
Behavioural genetics may also help us to understand crime and identify those who may be more likely to commit it.
If someone has a dysfunctional MAOA gene and is placed in an adverse environment, such as an abusive upbringing, 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 criminality decreasing.
In general, this area of study helps us to understand human behaviour. Understanding the importance of genetics when it comes to behaviour is as important as identifying how environmental and situational factors affect behaviour, as behaviour is often a combination of both genetics and environment.
Animal behaviour is thought to have evolved due to natural selection over generations. This idea was originally coined by Charles Darwin in his book 'On the origin of species.' Behavioural traits change over generations much like the physical characteristics of organisms do.
It is likely that aggressive behaviour is a result of evolution, as more aggressive animals would have a better chance of surviving until mating age and passing on their genes to the next generation. This is because aggression would allow easier access to food and the ability to catch prey or deter predators. Species that do not adopt beneficial behaviour such as aggression are more likely to go extinct.
The four principles of evolution are as follows:
Variation: Variation is the naturally occurring differences between individuals of any given species. Within species, individuals have some degree of variation in terms of physical and behavioural characteristics, with some individuals being more aggressive than others or differing in size.
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. Some individuals will have traits that aid survival, such as a larger size, which will allow them to survive and reproduce, while others may inherit traits that allow them to reproduce more, or allow easier access to mates. 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. Some species, particularly those with shorter lifespans such as microbes and viruses, may see notable changes within just a few years, while other species such as mammals tend to change over millions of years.
These principles apply equally to genetically inherited behaviour as they do physical characteristics.
Prey animals such as deer have evolved both physical and behavioural adaptations to aid in the detection and avoidance of predators. Physically, they have evolved long, thin legs for running and lateral eye placements, and behaviourally, they 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.
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 as well as the rapidly changing environments humans find themselves in.
Our ability to form complex societies that simultaneously shape and are shaped by human behaviour is also a result of evolution. This is arguably as important as evolution itself, as society has been shown to influence human behaviour far faster than evolution.
The existence of law, education and the economy have huge effects on behaviour. Law deters individuals from committing immoral, dangerous acts, while education further develops our reasoning skills and the economy keeps us busy and allows us a safer way to provide for ourselves and our families.
Some genetics have been found to influence human behaviour, for example the MAOA gene which was investigated by Brunner.
Psychologists investigate the genetic basis of behaviour in order to find out more about the origins of human behaviour and ways in which we can measure human behaviour.
Genetics do contribute to human behaviour, but human behaviour is a combination of both genetics and environment.
A genetic basis is when the foundation of a concept is based on genetics.
An example of behaviour genetics is research into autism, which attempts to understand it by analysing the genetics of individuals with autism.
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