Edexcel Psychology for A Level Year 2: Student Book

The debate: Nature versus nurture To what extent is any behaviour explained by ‘nature’, that is inherited (genetic) factors or by ‘nurture’, that is factors such as experience and the environment? This is the question the nature–nurture debate tries to answer. Nature Inherited predispositions People often employ ‘nature’ arguments in daily life to explain differences between people: ‘It’s not his fault, he was born that way’, ‘She’ll grow up to be a bright spark like her mum’. These are justifications based on the idea that we inherit predispositions. These may be present at birth, or the genes may determine our development so that the inherited tendencies only become evident as we mature. Both are the product of our genetic endowment. For example, the cognitive problems seen early in life with dyslexia, and later in life with Alzheimer’s disease, are at least in part governed by nature. Genes and evolution The ‘nature’ argument is linked to the biological approach, focusing on genes and evolution. Behaviours which have evolved through natural selection must be governed genetically so such examples support the nature argument. For example, in our distant ancestors males who aggressively guarded their partners may have been reproductively more successful. Therefore, this behaviour has been naturally selected (Y1 page 104). Innate behaviours Instinctive behaviours are useful (as they are the product of evolution) hence we tend not to exhibit many individual differences in these responses. For example, human babies are born with the innate ability to suck when the roof of their mouth is touched. This helps to ensure that they feed quickly and effectively, without having to learn how to obtain milk. Innate reflexes are often the simple reactions that become the unconditioned responses in classical conditioning, such as blinking or salivating. Nurture Many ways to learn The environment can influence our behaviour in different ways, as illustrated by the three learning theories. In classical conditioning, the environment offers neutral and unconditioned stimuli. In operant conditioning the consequences (of rewards or punishment) are from the environment. In social learning, models and their possible sources of vicarious reinforcement are again environmental. These environmental features will influence how we learn to behave. For example, childhood behaviours that are reinforced will tend to be the ones we repeat more frequently. Experience The environment provides more than just opportunities to learn. The chemical environment experienced by a foetus can affect it even before birth. For example, levels of hormones can affect brain development. Our cultural and family environments come under the banner of ‘experience’. They provide opportunities, sources of support and expectations which affect our thinking and hence our behaviour. For example, a person living in a multicultural society is likely to behave differently towards ethnic groups than would a person from a socially narrower background. This could affect prejudice. Applying your knowledge An example of a synoptic exam question linked to nature– nurture: Evaluate whether behaviours are caused by nature or by nurture. (20) The paragraphs below illustrate how you might answer this: Some evidence strongly supports nature, showing that genes control characteristics such as mental illness. In an adoption study, Tienari et al . (1994) found that the adopted children of biological mothers with schizophrenia had a 9.4% risk of developing schizophrenia whereas the rate for adopted children of non-schizophrenic mothers was only 1.2%. The greater risk for those with affected biological mothers shows nature at work. (64 words) Both nature and nurture can affect the same behaviour, and this can be shown in the same study. Ludeke et al . (2013) used self-reports to test parent–child relationships. They found that as the children grew older, nature effects became less apparent – the parents were having less effect on their behaviour during adolescence, but this was in part because the children were becoming more like their parents, a change which was under genetic control, so demonstrated the effect of nature. (80 words) Many studies show that nature has a strong influence on our behaviour. There is a major flaw in such research – if all the people tested share very similar environments (such as they all have reasonable levels of education) it is inevitable that there are large ‘nature’ effects. Consider this – if everyone smoked exactly 20 cigarettes a day, this would mean no variation in the environmental factor and therefore all differences in lung cancer would appear to be genetic – even though the main cause is cigarettes (environment). (Example from Bentall 2017) Testing the nature–nurture debate You have learned about the methods used to disentangle the effects of nature versus nurture, such as twin and adoption studies, and more recently genome-wide association studies have been used to study nature. In contrast, cross-cultural research is often used to study the effects of nurture. These methods were discussed in the Research methods chapter in our Year 1 book (pages 204 and 218). Evidence for nature Twin study evidence relating to the risk of schizophrenia in MZ twins has showed that, if one twin has schizophrenia, their co-twin is at least 42 times more likely to have schizophrenia than someone in the general population. In DZ twins the risk for a same-sex co-twin is only 9 times as likely (Gottesman and Shields 1966, Y2 page 43). As the risk for an MZ co-twin is very much higher than for a DZ one, it can be concluded that schizophrenia is partly controlled by genes, i.e. nature. Evidence for nurture Evidence of cultural differences supports the nurture argument. The people of !Kung San in Southern Africa discourage aggression whereas the Yanomami people of Brazil accept aggression as a way to access status in society (Wolfgang and Ferracuti 1967, Y1 page 105). If the control of aggression was genetic, i.e. nature, the differences between cultures would be far smaller. Evidence for the interactionist approach Whilst studies may show that either genes (nature) or the environment (nurture) are more important, most show that both have a certain amount of influence. For example, Mara Brendgen et al . (2005, Y1 page 114) investigated the development of aggression using a twin study. This evidence showed that whilst physical aggression was mostly controlled by nature, social aggression was largely the product of nurture. Each time we have just provided two example paragraphs to illustrate how you might tackle an exam question. However, for 20 marks, you would probably need six paragraphs such as those here, with a balance between points for and against. Nature–nurture 23