Edexcel AS Psychology - Biological - Methodology

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  • Created by: Ally
  • Created on: 13-03-12 12:25


Psychologists within the biological approach look for genetic explanations for who we are, to support their argument that our behaviour is determined by our biological make-up. An excellent way to look at this is to study twins or children who have been adopted; any similarities between parent and child behaviour can be because of their genes.

Twin Studies

Twin studies are used for comparing two types of twins; mono-zygotic (MZ, identical twins from one egg) and di-zygotic (DZ, twins from two eggs who share the womb, they share 50% genes like all ordinary siblings).

 When studying twins, both of the twins will share very similar environments as they are born at the same time, to the same family and will be treated the same. Therefore, any differences in behaviour must be down to the twin’s biological make-up. For example, if the behaviour of MZ twins is more similar than the behaviour of DZ twins, it can be concluded that the behaviour is a product of nature, rather than nurture.

However, there are cases when MZ twins are separated at birth and are raised in completely different environments to each other. Therefore, if behaviour is found to be similar, then it is likely that it is due to genetics.


Evaluating Twin Studies

·         Twin studies provide a solid natural experiment, in which nurture is kept the same whilst genetic makeup varies, so any differences between twins can be assumed to be due to biological influences.

·         Twins that take part in twin studies are often chosen via a volunteer sample and therefore may not be representative of all twins. Additionally, participants chosen via a volunteer sample may show demand characteristic where they alter their natural behaviour to please the researcher by showing them what the researcher wants to see.

·         It can also be suggested that MZ twins are more likely to be treated the same because they lookalike, more so than DZ twins because they don’t look the same. Therefore, MZ twins have a more similar environment than DZ twins, making it more difficult to draw conclusions about nature and nurture influences.

·         Samples sizes of twins are small and therefore we cannot generalise the results we


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