Discuss genetic and environmental influences on behaviour. (22)
There has been a debate in psychology regarding nature (genetics) and nurture (the environment) and whether one of these explanations alone determine human behaviour, or whether there are other factors influencing our actions.
There are two different stances that people take on whether language development is genetic or environmental. Nativists believe that the capacity for language can be classed as ‘innate’. Whereas empiricists suggest that, it is environmental variables that play a vital role in language development.
It would be ethically impossible to study behaviour in total isolation in order to determine whether genetics or environmental influences for our behaviour. The closest research recorded, focusing on this case is a girl named Genie (1970); who was socially isolated for the first 13 years of her life, by her father. Genie’s case presented researchers with a unique opportunity. Psychologist James Kent described Genie as a ‘profoundly damaged child’ as it was discovered that she could hardly walk and could only speak around 20 simple words.
It was suggested that although she started learning single words. In most cases it is thought that after a few words have been acquired it is then followed by what is called language explosion. However, this never happened for genie her language abilities didn’t improve, and she appeared unable to apply grammatical rules and use language in a meaningful way.
Contradicting this argument, Nativist Chomsky suggested that acquisition of language could not be fully explained by learning alone. Genie’s inability to use grammar (which Chomsky suggests is what separate’s human language and animal communication.
Lenneberg also suggests that like many other human behaviours, the ability to acquire language is subject to what is known as critical periods. Supporting Genie’s case study. He says the critical period for language acquisition lasts until around the age of 12/13. He opposes Chomsky’s LAD device. He argued, the organisation of the brain becomes set and no longer able to learn and utilise language in a fully functional manner. Therefore, he suggested that language is a human instinct and all normal children develop language without conscious effort or formal lessons, and by the age of three they speak in fluent grammatical sentences, outperforming the most sophisticated computers.
In conclusion, it was believed that language was learned through mimicry of our parents and reinforcements; this was led by Skinner who suggested that ‘if an organism responds in a certain way to a stimulus and a gets a positive reinforcement, its behaviour will stop. Thus, any kind of vocal output can become part of language. This supports the empiricist’s suggestions.
Environmental influences can be sub-divided into the biological environment and the psychological environment. The biological environment affects our physical development and includes things such as malnutrition and drug abuse by the individual’s pregnant mother. It is not a genetic influence, as drug abuse is an environmental factor which affects how some of our genes are expressed. An example of this is a study of identical twins separated at birth, where one was malnourished throughout childhood, and epigenetics are changes in the phenotype or gene expression caused by the environment or anything other than the underlying DNA sequence such as stress and malnourishment, which can be passed on to future generations, such as what occurred here.

Therefore, the two twins studied could have children of different body weights even if they had identical diets due to the epigenetic material passed on from their fathers. The psychological environment includes a person’s experiences, such as the quality of the relationship between child and parent, as well as socio-economic status.

There are many examples of genetic and environmental influences on behaviour. Studies into mental illnesses e.g. unipolar depression and schizophrenia have shown evidence to support the genetic argument, as in Joseph (2004)’s study the concordance rate for schizophrenia is about 40% for MZ twins and only 7% for DZ twins, suggesting genetics have a large influence on the development of schizophrenia. However, Bateson believed in the nurture argument and developed the theory of double-bind communications, where a parent may say one thing in a positive manner but act in a completely different manner, e.g. asking their child to come to them but with their arms folded as though they didn’t want them to come close. R.D. Laing argue that madness was a reasonable response to insanity in the environment.

There is clearly a significant environmental component to the development of mental disorders, and Beck’s cognitive theory that depression is a disturbance in thinking rather than mood from outside influences like a bad grade in an exam is an example of how the environment can make you become depressed. The diathesis-stress model which represents both nature and nurture can also demonstrate this, as individuals who have a genetic vulnerability for a particular disorder may only develop it under certain conditions. Tienari et al found that adopted children with schizophrenic biological parents were more likely to become ill themselves only if the adoptive family were rated ‘disturbed’, so the illness only manifested under certain environmental conditions. This is an example of how nature and nurture are no separate, but interacting components.

Evolutionary explanations are based on the principle that a behaviour or characteristic which promotes survival and reproduction will be naturally selected because it is adaptive and so the genes will be passed on to future generations. Buss investigated this, and found that certain aspects of mate choice behaviour are universal e.g. women’s tendencies to value ambition and industriousness more than males, as women are said to require support from their partners. The fact these behaviours are universal suggests a genetic basis, however genetic behaviours can be modified by culture. Buss found exceptions to the general tendencies as 22% of women didn’t value industriousness more than males – cultural relativism. The findings by Buss are deterministic as they support the theory that our behaviour is pre-determined by genetics, however evidence has been found to suggest that this is not the case in many areas of psychology.

In the case of aggression, Bandura’s view was that aggressive behaviour is mainly learned through observation and vicarious reinforcement – social learning theory, supporting the nurture debate. He suggested that this allows us to learn the forms aggression take, the situations that produce it, targets towards the aggression etc. and his study using a Bobo doll and measuring the aggressive acts of children after observing a model illustrates this theory. However on balance, biological factors are not ignored in this theory – a person’s genetics could create potential for aggression and it is how to express this aggression that is learnt. Evidence to support the biological factors includes Coccaro et al’s study who looked at twin pairs and found nearly 50% of the variance in aggressive behaviour could be attributed to genetic factors.
Genes and the environment could interact. Genes may affect behaviour directly e.g. a gene for schizophrenia creates vulnerability for the disorder; however Plomin et al suggested indirect effects of genes.

A reactive influence is where genetics create a microenvironment, e.g. a child who is genetically more aggressive provokes aggressive responses in others, becoming part of the environment affecting development. Passive influences are where parent’s genes determine an aspect of behaviour e.g. a parent with a genetically determined mental illness creates an unstable home environment. Active influences could also be at work where as children grow older they seek experiences and environments suited to their genes and their behaviour differs from their siblings for example as they do not share this environment e.g. the same school if one sibling is at primary school and the other is at high school, so behaviour changes as a result of these experiences.