Stcmpsy



What is meant by ‘genetic influence’? (3)OR What is meant by ‘environmental influence’? (3)Critically consider the balance of genetic and environmental influences on human behaviour (22)Essay Plan for part b)Introduction -This debate is of interest to psychologists because we are interested in the extent to which our genes influence aspects of behaviour such as intelligence, mental illness or personality for example. More recently it is widely accepted that an interaction of both genes and environment influence human behaviour however prior to this biological psychologists took a very reductionist view that genes may be a sole influence on behaviour and behaviourists took an extreme view of environmental determinism. Hence this debate was until recently often termed the nature vs nature or learned/innate debate. AO1 The interaction of the environment with our genes can be shown through the recent discovery of epigenetics and differences between genotypes and phenotypes. For example identical twins with the same genetic make-up (geneotype) who are reared apart can end up with different physical characterisitcs (phenotype) due to environmental factors such as diet or pollution. These factors have the effect of switching on certain genes e.g which govern height of a person, which may then be inherited by the next generation.AO2 However it is also thought that our genes can affect our environments directly and indirectly. For example Plomin et al (1977) suggested that infants can create microenvironments based upon genetic tendencies such as aggression. Furthermore a genetically determined mental disorder of a parent could affect the environment of a child triggering the same disorder in the child. Scarr and McCartney (1983) suggest that genes can influence what kinds of activities a child might prefer and therefore select as they get older. Therefore they ‘niche pick’ and actively create their own environments based upon genetic factors. AO2 This explains why siblings who share 50% of their genes and the same environment do not show high concordance rates on characteristics but it does not explain why identical twins (MZ) do not show 100% concordance.AO1 When looking for the extent of genetic and environmental influences on behaviour biological psychologists have used twin studies or gene mapping to gather heritability estimates for a certain characteristic such as suffering from Schizophrenia for example. This is an estimate of the extent of a genetic cause which then also gives an indication of the extent of environmental causes also. For example Chorney et al found specific genes associated with high IQ. AO2 However this is controversial as other studies such as Turkheimer et al suggest that socio-economic status has a bearing on IQ which is an environmental factor. AO2 This shows that environmental enrichment supplied by more ealthy parents has the effect of ensuring that genetic IQ is maximised.AO1 Twin and adoption studies suggest that heritability of mental disorders is high. For example Joseph (2004) suggested concordance rates for MZ twins is 40% for schizophrenia.AO2 However the Diathesis Stress Model shows that genetic predispositions towards the illness are increased by environmental factors such as family conflict for example.AO1 Behaviourists since the 1930s have suggested that most behaviour is due to environmental factors such as reinforcement. For example Bandura’s classic bobo doll study showed the effect of vicarious reinforcement on the aggression of children.AO2 However Coccaro et al (1997) suggest 50% of variance in aggressive tendencies is due to genes.AO1 Further studies have shown the extent that our environments can affect our actual biology. For example Blakemoor and Cooper (1970) raised kittens in an enclosure restricted to either vertical or horizontal lines. After five months the kittens were unable to see lines other then the ones they were exposed to meaning that their visual cortex had developed differently as a consequence of their environment.AO2 In support of this idea Maguire et al (2000) carried out brain scans on London Taxi drivers and found enlarged hippocampi (responsible for long term memory) which he suggested was due to learning London taxi routes (the knowledge). Conclusion – Psychologists now widely agree that both genetic and environmental influences on behaviour are entwined for the reasons discussed in this essay. However they still debate the extent of these influences and research studies often contradict each other. There is evidence of genetic involvement in intelligence and mental disorders but environmental influences cannot be discounted. There is also evidence of environmental influences on personality traits like aggression for example however the extent that these are rooted in genetic differences is still unknown. ................
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