We all agree that we are influenced by both genes and experience, but the debate is how important each is. For physical features, such as eye colour, the question poses little contraversy; the genetic factor predominates.
For psychological characteristics, however, the question is more controversial and the answer is less obvious. At the heart of the debate, lies the question of the relative contributions of nature and nurture.
- The emphasis is on the role of genes, hormones and inborn characteristics on behaviour.
- Associated with nativists who argue that individuals are born with an inherited blueprint.
- The implications are that the environment has little to do with individual development, and there is little anyone can do to change what nature has provided.
- Focuses on how learning and experience can influence behaviour.
- Associated with empiricists, who believed that the baby's mind at birth is like a blank slate, on which experience will write.
- The implications are that behaviour can be changed through manipulating reinforcement and the environmental conditions. Anybody can be trained to do anything.
Nature or Nurture?
Psychologists now do NOT adopt an extreme position of either nature or nurture as an explanation of behaviour, since both are essential for any behaviour, and it can't be said a particular behaviour is genetic and another environmental.
It would be impossible and illogical to seperate the two influences as they interact in a complex manner.
Although we cannot say that a specific behaviour in any individual is mostly due to heredity or mostly environmental, we can say that the difference between two people's behaviour and physical characteristic is mostly due to heredity or the environment.
The debate attempts to investigate the relative contributions of nature and nurture in individual differences and to understand the interactions between them.
Methods of investigation
- Twin Studies
Twin studies are designed to produce a heritability estimate: a statistical estimate of the proportion of the total variance in some trait within a group that is attributable to genetic differences among individuals within the group. Eg, if the hertiability estimate for IQ was 90%, it would mean that 90% of the differences between people's IQ were due to inherited factors
Twin studies look at the concordance rates between MZ and DZ twins either reared apart or together
- Adoption Studies
Another method that investigates the heritability of a particular trait is adoption studies, which compare adopted individuals with their biological and adoptive parents.
If an individual is found to be more similar to their bio parents, eg on intelligence, than to their adoptive parent, this suggests that intelligence is inherited.
In twin studies, however, there is a:
- High concordanance/appearance similarities - may be treated the same due to this + could be down to environment
- Share the same environment which could influence behaviour
- Hardly ever find 100% concordanance, displaying that some environmental factors must be involved
- Also prenatal factors and different individual experiences need to be taken into account.
Shared and unshared environments: Findings of studies of MZ twins reared together do not show a perfect concordanance rate, this has prompted psychologists to focus on the unshared environments of siblings. Individuals from the same home may have very different experiences.
For example, they could be treated differently by parents, siblings, have different social opportunities, different friends and teachers, make different subject choices and have different life experiences.
Even having the same experiences may have very different effects on each person, creating different environments. Elder (1974) found that paternal unemployment during the great depression had different effects on a child depending on their age/sex.
Also, for example, a baby who is more sociable may attract more affection and stimulating care than a more difficult baby.
According to CONSTRUCTIVISM, people activley create their own environment and experiences. They create and shape environments best suited to their own propensities.
PKU displays the interaction between heredity and the environment - PKU is an innate disorder that can be controlled by environmental factors, such as diet.
Interaction: Heredity and environment
Chomsky's theory of language acquisition claimed each child is born with an innate potential to acquire language, yet the particular language we learn and the fluency with which we command that language is due to the environment.
Anataski argued that both heredity and the environment were necessary for the person to exist; therefore both must exert an influence on the person. While some research attempted to investigate the relative contributions of innate and environmetal factors, most now accept the two influences form a continuum and interact with each other, they are virtually inseperable.
Genetic influences are affected by environmental factors, similarly enviromental experiences are mediated by innate abilities and by the physical structure of the body
Nature Supporting Studies
Gender: Evolutionary explanation: females care for the young whereas males protect the species due to their greater physical strength. These differences are clear from the moment of conception. This is supported by BUSS, who investigated the heterosexual male preferences of men and women in 37 countries, finding evolutionary traits such as financial security in men and chasity in women were universally apparent.
Masculine and feminine traits are attributed to the action of hormones. Testosterone is responsible for the development of external male sex organs and brain differences between men and women. DIAMOND and Sigmundson found that when David Reimer reached puberty, he could not be changed into a female. Diamond also found that when pregnant rats were injected with testosterone, they behaved aggressivley.
There is greater hemispheric specialisation for men than women. In males, the right hemisphere is dominant for spatial skills, whereas in females, both hemispheres are active when completing spatial tasks. Also, regions of the hypothalamus are larger in heterosexual males than in females. This could be the reason for women being more coy and men more promiscuous.
Nature Supporting Studies
Schizophrenia tends to run in families. GOTTESMAN and SHIELDS's meta analysis concluded that the concordance in twins was 46% for MZ and 14% for DZ. NOT 100% however.
Adoption studies seperate genes and environment. There is a 16% incidence of schizophrenia in adopted children (Heston 1966).
Neurochemistry: the dopamine hypothesis enforces that schizophrenia has a biological origin. Evidence shows that, when taken by healthy individuals, drugs that increase dopaminergic activity in the brain, result in psychotic symptoms (such as hallucinations).
These drugs also exacerbate psychotic symptoms in people with schizophrenia. Neuroleptic drugs that block the dopaminergic neurons reduce psychotic symptoms. Seeman et al also found six times the density of D4 receptors in the brains of people with schizophrenia. However, it is hard to determine cause and effect.
Nurture Supporting Studies
Gender: Social Learning Theory states that behaviour is shaped in a social context through observation, imitation and reinforcement.
MEAD supports this with her cross cultural study, in which she found three tribes in New Guinea had altered gender roles when compared to Western society. The Arapesh tribe were both feminine, the Mundugmor tribe were both masculine, and the Tchambuli tribe had reversed gender roles when compared to Western society.
Furnham and Farringher found that TV adverts enforced sex role stereotypes.
MONEY and EHRDHART sucessfully socialised a child into the opposite sex.
BEM found many individuals were androgynous.
Nurture Supporting Studies
Schizophrenia: Bateson suggested that communication between parents and offspring was sometimes 'double blind.' Parents could say one thing but their body language could suggest the other. The child learns to not trust their own feelings/perceptions.
Family socialisation theory: state that families sometimes fail to provide a stable environment as appropriate role models: Schismatic familes (conflicts between parents result in competition for the affection of family members and a desire to take control) and Skewed families (one parent abnormally dominating. The children are encouraged to follow the dominant partner, impairing their cognitive and social development.)
Expressed emotion: high face to face contact between patient and family was found to increase risk of relapse, attributed to the realtives' emotional over-involvement. When hostility, crticism and emotion are high in a household, the patient is more likely to relapse. BEBBINGTON AND KUIPERS found that 52% of families were high EE. Replase in the EE families averaged 50%, whilst in the low EE, it was 21%. This displays EE is a significant risk factor in relapse rates.
Labelling: Szaz argues schizophrenia is a result of a socialisation process. Using terms such as 'treatment' and 'illness' is a form of social control. Schizo becomes a self-fulfilling prophecy. Rosenhan found pseudo patients could convince doctors they were schizophrenic, hospitalised for 7-52 days, and were stuck with the label.
Interactionist Supporting Studies
Biological predispositions guide development in certain directions but experience influences how development manifests itself.
The bio-social approach to the development of gender identity moves away from the direct influence of physiological factors and focuses on the interaction of biological and social factors.
SMITH AND LLOYD found when a baby was presented as a percieved sex, mothers enforced sex role stereotypes through encouraging girls to play quitely with dolls and boys to behave more activley.
Schizophrenia: individuals may have a genetic predisposition to the disorder, but it's not certain they'll develop it.
Environmental factors are required to 'trigger' off this predisposition, and this is where social psychological factors, such as urban living and expressed emotion, may play a part. This combines both biological and environmental explanations.
Biological Psychodynamic Cognitive SLT Humanistic Behaviourist
Biological = Most extreme nature position, due to its focus on genetics and physical structures, such as the brain and hormone system. According to this approach, there is a continuing interaction between nature and nurture. Studies into hormones, such as Diamond/ Diamond and Sigmundson display the effect of hormones on behaviour and gender development. Also differences in the hypothalamus and the effect on behaviours displays how physical structures alter behaviour. Buss also offered support for evolutionary theory. Does not take environmental influences into account.
Psychodynamic = Is more nature than nurture. Freud stressed the biological nature of humans, the focus being on the instinctual drives of sex and aggression. The Ego, Id, superego and unconscious are all innate. The stages of psychosexual development are also innate. However, there are environmental influences. It is the reaction of significant others to these biological urges that produce long term effects on the child's personality. However, innateness holds more of a role in determining behaviour.
Cognitive = Cognitive psychologists are interactionist in their approach. Their focus is on innate info processing abilities that are constantly refined by experience. Eg, Piaget proposed that the stages of cognitive development are determined by nature; the order is invariant and roughly age related. Innate schemas develop and expand through continous interaction with the external world. Knowledge of the world is stored as schemas not in the form of single concepts, but a cluster of relevant ideas, including past experiences.
Martin and Halverson showed that children do use schemas to help them make sense of their world, and discard gender inappropriate, schema inappropriate schemas. Supports nurture.
SLT = SLT assumes behaviour is learnt through a combination of observation of other's behaviour and expectation of reinforcement or punishment for copying a behaviour. It enforces the role of the environment on a person's behaviour. Inherently, we are a 'blank slate', and our behaviour is modifiable through environmental factors. It differs from behaviourists as it acknowledges the cognitive processes that have an effect on behaviour (innate). Bandura's study also displays how innate characteristics, such as aggression are imitated. It is less deterministic or reductionist than behaviourist.
Humanistic = The humanistic approach believes that life's main motive, the need to self-actualise, is innate. However, the approach believes that humans are influenced by environmental factors. Eg, if a person is presented with unconditional positive regard, and the conditions are favourable, then progress toward fulfilment will occur. Maslow refers to favourable conditions for self-actualisation. The fact that few people reach the pinacle of the hierarchy shows the powerful force of nature. Also, very few people experience unconditional acceptance from others as described by Rogers.
Behaviourist = Extremley 'nurture' orientated. Believes people are a blank slate on which experience writes, and behaviourists (unlike SLT) do not take innate mediational processes into account. This is supported by Little Albert, a baby where fear was sucessfully conditioned into it's behaviour, enforcing that behaviour can be manipulated by changing reinforcement and environmental conditions.