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Critically consider research into factors associated with the development of intelligence test performance. (24) Researchers have tried to isolate the factors associated with the development of intelligence test performance by studying the IQs of separated twins. The idea is that if the IQs of MZ twins reared apart are high, then this must be due to the genes they were born with rather than the different environments into which they were put. Correlations of between 0.7 and 0.8 have been reported by a variety of researchers (e.g. Bouchard and McGue (1981) and Pederson et al (1992)) which has led them to conclude that intelligence has a strong genetic component. ...read more.


We would also need to understand how this gene interacts with other genes in order to be effective. In relation to the environment studies, there is no indication of how the environmental factors said to be helpful by researchers such as Sameroff and Seifer (1983) actually cause intelligence test performance to rise. We might be able to understand how style of verbal interactions might affect intelligence test performance. Hart and Risley (1995) show how children perform better on IQ if their parents tend to use a wide vocabulary, use language with a high information content and use questioning as opposed to directive language. ...read more.


However, half of the separated twins in Pederson et al (1992) were separated after the age of one year and Kamin (1977) found that many cases of separated twins had spent a substantial amount of time together, perhaps because both were raised by relatives. Therefore, we might suggest that some of the high levels of correlation identified by separated twin studies can be explained by environmental factors. Indeed, when Ceci (1990) tried to control for these factors, he found that the correlation for the IQ scores of separated twins was reduced to 0.27. Given that these problems exist, it seems more sensible to try to understand how these environmental and genetic factors might interact rather than trying to separate them out, which appears to be all but impossible. ?? ?? ?? ?? ...read more.

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