The role of both nature and nurture in psychology.
Nature is the view that behaviour is the product of innate biological or genetic factors. For a long time, psychologists have known that certain physical characteristics, such as eye colour, skin pigmentation and certain diseases (e.g. Huntingdon’s) are biologically determined and the result of heredity (or genetic inheritance). Heredity is the process in which traits are passed down from one generation to the next. Furthermore, characteristics like height, weight, hair loss, life expectancy and vulnerability to specific illnesses are positively correlated with genetic relatedness. This has led psychologists to investigate whether psychological characteristics are also “wired in” before we are born.
This is known as the nativist position, and the basic assumption is that the characteristics of the human species are a product of evolution and that individual differences are the result of each person’s unique genetic code.
For example, family, twins and adoption studies show that the closer the relatedness of two people, the more likely it is that they will show the same behaviours. For example, the risk of being diagnosed with schizophrenia is approximately 1% of the general population. However, Gottsman and Shields (1991) pooled the results of around 40 family studies and found that the risk increases to 46% for those with two parents who have schizophrenia. Also, Joseph (2004) pooled the data for schizophrenia studies conducted before 2001 and found an average concordance rate of 40.4% for MZ twins and 7.4% for DZ twins, highlighting a significant genetic component.
Characteristics and differences that are not observable at birth, but which emerge later in life, are regarded by nativists as the product of maturation, as we have a “biological clock” which switches certain behaviours ‘on’ or ‘off’ in a pre-programmed way. For example, Huntingdon’s disease is a genetically transmitted disorder that usually emerges between the ages of 30 and 50, although it can appear at any time since the genetic cause is innately present.
Evolutionary explanations also emphasise the importance of nature as they assume that behaviours or characteristics which increase our chances of survival and reproduction will be naturally selected; the genes for these characteristics or behaviours will be passed on, as they provide an adaptive advantage. For example, Bowlby proposed that children come into the world biologically programmed to form attachments because this will help them to survive. This suggests attachment behaviours are naturally selected, and passed on as a result of generic inheritance (heredity mechanisms).
Nurture is the view that behaviour is the product of environmental influences.
The environment is seen as everything outside the body which can include people, events and the physical world. Environmentalists (also known as empiricists) hold the assumption that the human mind is a tabula rasa (a blank slate) and that this is gradually “filled” as a result of experience. This view was first proposed by John Locke in the 17th Century and was later taken up by behavioural psychologists. For example, John Watson (1913) famously wrote:
“Give me a dozen healthy infants, well-formed, and my own specified world to bring them up and I’ll guarantee to take any one at random and train him to become any type of specialist I might select–doctor, lawyer, merchant-chief, and yes, even beggarman and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.”
According to environmentalists, psychological characteristics and behavioural differences that emerge through infancy and childhood are the result of learning.
For example, behavioural psychologists explain attachment in terms of classical conditioning, where food (unconditioned stimulus) is associated with the mother (neutral stimulus), and through many repeated pairings, the mother becomes a conditioned stimulus who elicits a conditioned response in the child. Therefore, the child forms an attachment based on the pleasure experienced as a result of being fed.
Bandura argued that aggression is learned through observation, vicarious reinforcement and imitation, and is therefore explained by Social Learning Theory. However, he did acknowledge that the urge to behave aggressively might be biological, which suggests a more interactional approach.
Environmental explanations can also partly explain the occurrence of schizophrenia. Batson et al. (1956) proposed the Double Bind Theory which suggests that schizophrenia is the result of disordered communication within the family, where one. This is where one instruction is given overtly to a child (e.g. a mother says ‘come to me’) while another instruction is given covertly (e.g. the mother’s manner and tone of voice are rejecting). Prolonged exposure to such interactions prevents the development of a coherent construction of reality, and in the long run, this manifests itself as schizophrenic symptoms.
Recently psychologists have begun to question whether human behaviour is due to heredity factors (nature) or the environment (nurture). It is now widely accepted that heredity and the environment do not act independently and both nature and nurture are essential for almost all behaviour. Therefore, instead of defending extreme nativist or environmentalist views, most researchers are now interested in investigating the ways in which nature and nurture interact. The interactionist approach is the view that both nature and nurture work together to shape human behaviour.
The interactionist approach is best illustrated by the genetic disorder PKU (phenylketonuria). PKU is caused by the inheritance of two recessive genes, one from each parent. People with PKU are unable to break down the amino acid phenylalanine which builds up in the blood and brain causing mental retardation. However, if the child is diagnosed early, they are placed on a low protein diet for the first 12 years, which helps to avert this potentially lifelong disorder. Therefore, the disorder PKU (nature) is not expressed, because of an altered environment (low protein diet – nurture).
In psychopathology, many psychologists argue that both a genetic predisposition and an appropriate environmental trigger are required for a psychological disorder to develop; this is set out in the diathesis-stress model. The diathesis is the biological vulnerability such as being born with a gene that predisposes you to develop a disorder. However, the disorder will only develop if there is an environmental ‘stressor’ to trigger it. Evidence to support the diathesis-stress model comes from the Finnish Adoption Study w which compared 155 adopted children whose biological mothers had schizophrenia, with a matched group of children with no family history of schizophrenia. The researchers also assessed the quality of parenting through questionnaires and interviews. They found that the group with schizophrenic mothers had a 10% rate of schizophrenia, but they also discovered that all of the reported cases of schizophrenia occurred in families rated as ‘disturbed’. When the family environment was rated as ‘healthy’, even in the high-risk sample (mother with Schizophrenia), the occurrence of schizophrenia was well below the general population rates. However, the environment was not the sole cause, as the low-risk children from ‘disturbed’ families did not develop Schizophrenia – so the environment alone was not enough to trigger the disorder. This research provides strong evidence that schizophrenia is best explained by looking at an interaction between genetic inheritance and environmental triggers, in this case, family environment.
Neural plasticity is another example of how nature and nurture interact. The brain can reorganise itself by forming new neural connections throughout life. Neuroplasticity is a term which describes the changes in the structure of the brain (nature), as a result of life experience (nurture). For example, Maguire et al. (2000) investigated the hippocampi volume of London taxi drivers’ brains. She found that this region of the brain was larger in taxi drivers in comparison to non-taxi drivers. Consequently, Maguire concluded that driving a taxi (nurture) actually had an effect on the size of the hippocampi (nature).
Nature and nurture can interact in a variety of ways, and three separate types of gene-environment interactions have been described by Plomin et al. (1977): passive, evocative/reactive, and active.
In passive gene-environment interaction, parents pass on genes and also provide an environment, both of which influence the child’s development. For example, highly intelligent parents are likely to pass on genes for intelligence to their children. They are also more likely to provide high levels of cognitive stimulation and a good education. These correlated genetic and environmental influences both increase the likelihood that their child will be highly intelligent.
In evocative gene-environment interaction, heritable traits influence the reaction of others and hence the environment provided by others. For example, a shy child (partly genetically influenced) may be less fun to other children, making other children less likely to want to spend time with him or her. This environment may result in the child becoming even more socially withdrawn.
In active gene-environment interaction, a child’s heritable traits influence his or her choice of environment. For example, an aggressive child may choose to watch violent films and engage in contact sports. This is known as ‘niche-picking’ and is one reason research has shown that the influence of genes increases as children get older.
Assess the argument that nature plays a greater role in human behaviour than nurture. (20) October 2017