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Discuss the role of genetics in the development of measured intelligence

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Discuss the role of genetics in the development of measured intelligence (24 marks) Genetic explanations of measured intelligence would suggest that intelligence is innate and hereditary, so we are predisposed to have the IQ that we have. One method of investigation into the role of genes is twin studies. Since monozygotic twins share 100% of their genes, it follows that if measured intelligence is entirely a result of genetic causes, then monozygotic twins will have the same IQ. Bouchard & McGue conducted a meta-analysis of many studies into the role of genetics in intelligence, and found a strong correlation between the IQ of identical twins raised together and apart (0.86 and 0.72, respectively). Even the twins raised apart had a higher correlation between their IQ than did fraternal twins raised together (0.62). This does indicate a genetic link, but since the research is correlational, it is impossible to infer causation. ...read more.


This indicates that biological factors are significant, but have a latent effect. This finding is duplicated by the Texas Adoption Project, which found no correlation between adopted children and their unrelated siblings by the age of 18. Thus, it may be that environmental factors are only significant in childhood, and through puberty it is the genetic factors that shape the person's intelligence. If intelligence is the result of genetics, it follows that there must be some gene or collection of genes that causes a higher IQ. A study of children with 'ultra-high' IQ scores revealed that a particular variant of a specific gene on chromosome 6 was twice as common in these children than in those with average IQs. However, even in the high IQ sample, the rate was only 46%, so there must have been either other genes or other factors involved in their intelligence. ...read more.


Black Americans are, statistically, much lower in socio-economic status than white Americans, so it may be this environmental factor that causes their IQ to appear lower on tests. All of the above research, however, assumes that genetics directly affect intelligence, but this may not be so: they may affect it indirectly. For example, if a person is genetically predisposed to have a personality such that they respond positively to others, it may be that others respond positively to their questioning about the world, and therefore their intelligence becomes more developed. This 'microenvironment' may result in a secure attachment with a parent, which itself may result in a higher IQ. As it also relies on others, it would also indicate that environmental factors are significant, as it is a form of reciprocal determinism, which may account for correlations between monozygotic twins of less than 100%. This is supported by Broungart et al., who found that the correlation between the IQ of children and their parents was higher when the parents were biologically related than otherwise, indicating a definite, but indirect, genetic link. Clive Newstead ...read more.

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