IQ and Heritability
According to studies conducted by researchers, it has been shown that genetic factors affect the IQ of a person, and specific genes that take part in influencing the IQ have been identified. The studies have also proposed that performance is affected by genetic factors. However, it has not been clear whether the genes that shape the IQ are the same genes that influence test scores and grades. The high heritability of intelligence proves to be a difficult subject because it may be perceived to imply that the communities or schools that perform poorly produce unfavorable results due to the immutable characteristics present in those populations. This may imply that the poor kids should be left alone just because they are created that way.
However, comprehending the reason why the school system is difficult for some people while being easy for others is important to enabling the researchers to come up with a system that suits the individual strengths of the communities and schools involved. Again, high heritability does not imply total heritability because there is yet another vital role of the environment that requires much consideration, an aspect that informs the scholars of the field of intelligence inheritability how the results can be improved through a change in the environment. A population exhibiting high rate of heritability may be interpreted as a symbol of equality in the sense that environment would be the dominant factor, or it can’t vary radically. For instance, taking height to be an example, people grow to be shorter or taller adults due to the combination of various environmental factors such as nutrition during their early childhood, with their genes.
A country that exhibits high inequality, where some of the children receive excellent or adequate childhood nutrition while the others starve, nutrition will have a very vital role in determination of the height that people can grow without considering their genetic make-up, since the children possessing the genetic ability to be tall may be stunted by unfavorable environment. Likewise, in a population where everyone receives excellent nutrition, the height of the people will largely be determined by the genetic heritability. Considering the effect of environmental factors to the IQ of a person, it is important to use the same perspective for education. When all the learners receive exactly the same quality of education and are exposed to similar good life at home, their tendencies and inherited traits will have an important role to play in their final results. When some of the learners receive better quality education as others receive poorer quality, the educational aspect will have an important role to play in determining the extent to which the learners can reach academically.
This also implies that an approximation of heritability among a population can’t be extended to another population. For instance, since the population of twin study may represent the overall population in the UK, it is possibly safe to come up with conclusions regarding the UK as a country. However, it is hard to conclude much regarding the exact rate of heritability in another country, though it may be expected that other factors apart from intelligence have very crucial roles to play in school results.
Referring to the ancient investment theory, intelligence may be categorized into two major classes, which are: crystallized and fluid. Differences present in fluid intelligence are believed to exhibit novel and reasoning on the spot, while the differences present in crystallized intelligence are believed to exhibit knowledge and skills that have been acquired previously. Crystallized intelligence, according to the investment theory, develops through investing fluid intelligence in a specific body of knowledge. There is a clear prediction of this theory considering genetics. In a vast population, where the educational experiences of the people differ, inheritance of the fluid intelligence is likely to be higher than the inheritance of crystallized intelligence. The investment theory makes the assumption that the fluid intelligence is relatively fixed and it is influenced heavily by genes, while crystallized intelligence depends highly on the learning opportunities and acquired skills.
Kees-Jan Kan and his colleagues carried out an analysis of 23 independent twin studies results carried out, totaling to 7,852 people sample. The study team investigated how the coefficients of heritability vary across particular cognitive abilities. The study majorly assessed the “Cultural load” of different abilities by considering the average percentage of the adjusted test items when the test was used in 13 other countries. According to the results of the study by Kees-Jan Kan and his colleagues, the societal demands have greater impacts on developing and interacting the multiple cognitive knowledge and abilities, therefore, leading to better correlations among each other, resulting to the general intelligence factor. For the sake of clarity, the findings do not seek to imply that the differences in intelligence are fully determined by culture. Various researchers have discovered that genes have strong influence to the structure of cognitive abilities, and they suggest that education, culture, and experience play major roles in developing intelligence than the assumptions of the mainstream theories of intelligence.
There is a possibility that the Western society has a learning environment that is homogenous, where all the school systems are similar. Again, everyone has undergone similar educational experiences, therefore, the only difference stems in the cognitive ability. The other probability is that there is some truth in the traditional investment theory, and crystallized intelligence, for example, general knowledge and vocabulary, is more cognitively important than looking for the solution of the abstract reasoning tests that are most complex. To prove this as the truth, vocabulary tests, for example, would have much dependence on the IQ than the fluid intelligence.
The researchers in behavioral genetics field, who often parse out the environmental and genetic sources of variation, sometimes operate using the assumption that environment and genotype do not co-vary, and are independent.
There are Black-White differences in the IQ test scores. While analyzing the data of the US Army, Charles Spearman, who is a British psychometrician, discovered that the extent of the black-white differences on a test was directly related to the correlation with IQ of the same test. Arthur Jensen formulated a full-fledged theory years later which he called “Spearman’s hypothesis”, which says that there is a direct proportion between the test correlation with IQ and the extent of black-white differences on cognitive ability tests. In the year 2005, Jensen, together with Philippe Rushton teamed up and made the case in a controversial paper that there is a proof that black-white differences are genetic in origin.