IQ ESSAY

Another way in which these factors have been researched is through adoption studies......

One problem with this research is that it is not clear what processes and mechanisms underpin the factors which are identified. In relation to the gene study by Plomin and colleagues, it is not clear what the gene Plomin has identified actually does in order to raise levels of intelligence. To understand this properly, we would need to know which factors in the environment would need to be present in order to make this gene effective. 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. All of these might help a child to develop thinking in a more advanced way. However, why other factors such as the number of children in the house should make a difference one way or the other is simply not clear.

One problem with this research is that it is very difficult to separate out genetic from environmental factors. For example, separated twin studies appear to be the perfect experiment because the similarity between the twins' scores must be genetic in origin. 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.