Individual differences in intelligence tests can be linked to either heredity or environment. Heredity consists of each person’s genetic inheritance, the instructions that tell your body to produce hair of a particular colour, in this context it is the impact on performance in intelligence tests. Environment consists of the situations and experiences encountered by people during their lives which impact the performance on intelligence tests Many psychologists have studied the relative contributions of genetics versus environment and this leads to the conclusion that individual differences in intelligence depend on differences in genetic endowment or differences in the environment.Twin studies are a useful way of assessing the relative importance of genetic factors and environment by comparing monozygotic twins (100% same genes) and dizygotic (also known as fraternal) twins (approximately 50% of the same genes).
If genetic factors influence individual differences in intelligence, identical twins should be more alike in intelligence than fraternal twins. Bouchard et al studied more than 40 adult identical twin pairs separated at a mean age of 5 months, and found their IQs correlated +.75. The similarity of the correlations supports the reliability and validity of the genetic basis of intelligence. Further research support would be Horn (1983) who reported findings from the Texas Adoption Project, which involved almost 500 adopted children.
The correlation between the adopted children and their biological mothers was +.28, and between the adopted children and their adoptive mothers was even lower at +.15. Both of these correlations although very low but they do suggest a greater role for heredity as the correlation between biological relatives was higher than between adopted relatives. However, one can question the validity of IQ tests.
Intelligence tests are not necessarily a valid measure of intelligence. They are culturally biased and narrow in scope because they fail to assess social or emotional intelligence. Consequently, the evidence is on differences in intelligence as assessed by intelligence tests, which is not necessarily a valid measure of intelligence. Okagaki and Sternberg studied ethnic groups in San Jose, California and found concepts of intelligence varied within a culture.
Asian parents emphasized the importance of cognitive skills in their conception of intelligence. In contrast, Latino parents argued that social-competence skills are of particular importance in their conception of intelligence. This creates difficulty in measuring intelligence because cultural bias is present therefore in the context of the role of genetic factors, intelligence test performance are culturally biased tests which can lead to invalid generalisation of results to collectivist cultures. The problem is that the IQ tests are ethnocentric, i.e.
biased to favour the culture in which they were devised, and so they are not a valid measure of intelligence in other cultures. Moreover, research into genetic factors associated with intelligence test performance take on a biological perspective, they reduce complex human intelligence to genes. A reductionist perspective as various behavioural, cultural and environmental factors is ignored. Some believe that evolutionary explanations describes factors which limit our free will and are therefore deterministic, in that it can be seen to imply that we develop intelligence in ways in which we are ‘naturally inclined’. Evolutionary considerations are irrelevant to a full understanding of the foundations of ethics. They hold that the admission of the evolutionary origins of human beings compels us to concede that there are no foundations for ethics.
This view points out that whether or not a intelligence trait is inherited, it does not affect whether it can be changed by one's culture or independent choice.Therefore, the evolutionary inclinations discard the development of our intelligence in our environment and only take into account the fact that intelligence in an individual is predisposed thus supporting the evolutionary perspective. Looking at the impact of environmetal factors associated with intelligence test perfomance, one can argue that environmental factors have a more siginificant impact than genetic. Flynn discussed evidence from 20 Western countries, all showing the Flynn effect: a rapid rise in average IQ in many western countries in recent decades. Flynn reported that there had been an increase of 2.9 points per decade on non-verbal IQ and of 3.
7 points on verbal IQ. Such large and rapid increases in IQ are due mainly to environmental factors, such as longer time spent in education and greater access to information. Skodak and Skeels (1949) provide strong research support for environmental factors associated with intelligence test performance. They followed the progress of 100 children born to retarded parents who were adopted before the age of 6. The mothers were mostly from low socio-economic backgrounds, but the children were adopted into homes that were above average both economically and educationally.
They found that moving a child from an impoverished to an enriched environment can produce long-lasting gains in intelligence of up to 25 IQ points. This reflects the contribution of an enriching environment to measures of intelligence. However, one can criticise the environmental perspective and argue that genetic and environmental factors are positively correlated. In regards to the Flynn effect, emphasis is placed on environmental factors however you can argue that individuals with the greatest genetic potential for intelligence tend to find themselves in environments favourable for the development of intelligence, the parents make choices for their kids to live and work in places that are compatible with the child’s genetic makeup. This makes it hard to disentangle the effects of genetic and environmental factors.
Therefore, enrichment programmes and investigations of the ‘Flynn’ effect would also be an effective way of evaluating the role of genetic factors on intelligence test performance.This tells us that research into environmental and genetic is based on subjective judgement, it is inconclusive and can be prone to research bias as conclusions may be manipulated to favour the environmental factors more then genetic in terms of intelligence test performance thus reducing the validity of the research.In addition, research into environmental factors can be criticized as being mechanistic as they reduce people to machines due to the assumption that the environment programs our intelligence. Not only is this reductionist and environmentally deterministic but it ignores the cognitive approach as there is a lack of scientific objectivity.
Moreover, research into environmental factors is also culturally biased such as the Flynn study. An emic approach is taken where there is ecological validity as IQ tests are designed to be test specific to the culture being tested, in this case the Flynn study supports western cultures as research was carried out in western countries therefore there is strong validity for environmental factors associated with intelligence test performance. However this results in the research not being representative for individualistic cultures. This means that the conclusions cannot be generalized to other cultures such as collectivist.
