The Gene for Intelligence
Since scientific advances can search directly in the genetic factors that could explain this or that psychological trait, studies abound. This was valuable to find genetic causes (partial) example of autism, but also other psychological disorders.
Regarding intelligence, an unimaginable scale studies were undertaken to identify genes that may have an influence on IQ. Robert Plomin and his colleagues at King’s College London and sifted several thousand genes in 2001. The results of their work are very disappointing: none of the studied genes can be linked with certainty to IQ. A new study by the same researchers in 2004 can hypothesize that a gene could be linked to-IQ … but with a portion of explained variation in the order of 1%.
The tentative conclusion that imposes, in view of publications, is that there is no gene for intelligence or even genes could explain a non ridiculous variations in IQ. Genes tested encode proteins generally known to act in the brain (not less than 6000 genes are potentially involved). When there are two forms of these molecules, it is assumed that this can have a visible impact on IQ … but this is rarely the case.
Another angle in relation to genetics is the study of psychological disorders. Those of these disorders with known genetic causes deterioration in general so deep psyche (not just IQ), as well as the body. One of the problems is probably best known as trisomy 21, caused by an extra chromosome 21. The effects of this anomaly are both physical (common disorders of vision and the immune system) and psychological. Children with Down syndrome show QI typically of the order of 55 wholesale, they can take 10 years what the school is designed for a child of 5 or 6 years. Thus, a mechanism for the mysterious moment, IQ is lowered by an extra chromosome.
Another less known genetic disease, the Williams-Beuren syndrome results from the loss of part of chromosome 7. Disorders are again both physical and psychological turning around with an IQ of 60, so quite close to that of subjects with Down syndrome … although the subjects are very different, both physically and mentally.
Reviews and cons-critical
The criticism of research on the heritability of IQ attack rarely the result itself, which has been verified by many teams trying to prove the opposite: there is no doubt that IQ is influenced by genes inherited from our parents (and possibly not transmitted mutations), but also, to a lesser extent, the environment, education, etc.. However, critics continue to pour in, but they take a different turn, and instead put into question the basis of the measure of IQ.
Williams-Beuren and Trisomy 21
Trisomy 21 is a genetic disease resulting from the presence of a third chromosome 21. The Williams-Beuren syndrome is a genetic disorder resulting from the loss of part of chromosome 7.
Subjects with these genetic abnormalities are psychological rather mixed. While their IQ neighbors, trisomy 21 have a significant language deficit and are often unable to tell from some pictures that they present a coherent story. On the contrary, they are quite capable of making puzzles or copy drawings correctly. Williams-Beuren topics show the table opposite: with a correct language, they are unable to organize visual fields. For example, trying to draw a house, they may represent the windows to the outside of the building, the roof or on the side.
The comparison of these two syndromes therefore leads to the conclusion that verbal and visual skills, both reflected in IQ, have distinct biological bases.
Been criticized e.g. IQ have no psychological interest. According to the proponents of this criticism, renounce research on IQ, which has no tangible reality and could not be used to spread dangerous ideas without profound meaning, within the population. This criticism is not admissible in the state. The value of IQ is at least twofold. From a theoretical point of view, IQ provides an example of biologically heritable trait overall psychological. From a practical point of view, the interest of IQ is evident in education. Most children reported early psychologists are not gifted as children, but because they have behavioral disorders. Often the teacher feels that the student is delayed. Through analysis of IQ, we can make the difference between a child who does not follow because it is late and one that does not follow for the reason inverse3. The second could skip a grade and the first increase to their benefit to both.
Another criticism of research on the heritability of IQ and its use is supported by the fact we do not know very well what is IQ. The meaning of this magnitude, intended to measure “intelligence” is in fact deficient, as recognized by all who use it. First, the IQ measure traits that would not take into account: it depends, for example motivation, interest in the type of questions, etc.. On the other hand, it does not measure certain quantities which, however, would intuitively classified as a factor of intelligence as the ability to understand music, or to perceive the emotions of others. IQ is a measure bastard, reaching only a part of what we tend to classify intelligence, and whose field overflows at the same time building on unrelated intellectual skills involved.
In a more precise meaning, often criticized IQ mixing characters quite independent. The example of trisomy 21 subjects and those with the syndrome of Williams-Beuren is rich in lessons about this (see box). It suggests that biologically distinct systems are at work in both poles and visual language. Two poles involved in the measurement of IQ total4.
These criticisms are not absurd, but remain low to justify total rejection of IQ. If the idea that it is usually IQ is a caricature, specialists question did not imagine that this tendency sometimes to confuse IQ “intelligence” in the usual sense. They are well aware that IQ is only partial and the impure intelligence5. Its practical and theoretical wins yet. Although IQ does not measure exactly what we want, it is precious and useful.
How to cope
All this of course does not solve the problem of ideological departure: IQ is partly inherited, it could be used to justify social inequality. Some teachers begin to wonder if education keeps a sense, when you consider it explains only a small part of the variation in IQ.
On the issue of education, we can make two responses: first, a small part is not nothing, besides the interpretation of this share remains fairly obvious. On the other hand, education is not the primary goal of increasing the IQ! In fact, IQ can be understood as a measure of learning skills. What you learn is quite another. Education should increase the knowledge, culture, understanding the world in which we live and all that can afford to be a good citizen. All this is relatively independent of IQ.
It must also be said that the heritability studies are based on virtually all western populations of children who all go to school. So the environmental variance corresponding to the total effect of school (compared to no school) is simply not measured (all that is measured is the variance due to different qualities of education ). We remake the same studies in African countries where only 50% of children go to school, she would reappear massively reduce heritability and perhaps because it is a relative variance.
On social inequalities and their supposed inevitability, the drift is to focus on IQ as if it was not an interesting quantity among others but as THE supreme value is wrong. A fallacy is at work particularly worrying in the speeches of those who want to justify inequality by noting that IQ influences in society and the social structure is legitimated.
What would we think of a nation of people who, after we had demonstrated that they were bigger than us on average, would assume they should rule the world? We would tell them that size is not a legitimate criterion of classification. If we take a step back compared to our culture, we can perceive the absurdity or at least the totally arbitrary idea that IQ (although good measure intelligence) can legitimize social distinctions. The usual criticisms against IQ may be taking the problem upside down: this criterion is not to throw away, but there is no objective reason to consider that it should take precedence over all other evaluation criteria.
One could even go further and say that because IQ is partly inherited, it cannot be a criterion of social distinction in a culture that pretends reward effort and merit.
Therefore continue to study the IQ, but fighting for it is not seen as an absolute value. No more than the ability to concentrate, gifts for music or rhetorical skills it is a legitimate criterion for classifying humans.