Factos affecting IQ

Factos affecting IQ

The IQ tests which are used to measure the intelligence of a person provide only approximations of the “actual” intelligence. This is because intelligence is indefinable and is hard for us to compute the concept. Furthermore, a few unrelated properties in theory are known to associate with IQ such as race, sex and height. However, the true connections between these factors is doubtful because of the properties does not automatically imply each other. Based on our research, we had found that the factors affecting IQ can be split up into biological and environmental.


Genetic variation

Many researches put an evidence which suggests that genetic variation has a crucial effect on IQ. This means that some of one's IQ is from the heritage. The relatives of probands with a high IQ shows a comparably high IQ with a much larger probability than the general population. In 1982, Bouchard and McGue reviewed such correlations reported in 111 original studies in the United States. Ranging from 0 to 1, the mean correlation of IQ scores between identical twins was 0.86, between siblings, 0.47, between half-siblings, 0.31, and between cousins, 0.15. From such data the heritability of IQ was expected to be at between 0.40 and 0.80 in the United States. This large boundary appeared because the heritability of IQ goes up through childhood and adolescence, reaching the peak at 0.68 and 0.78 in adults, leaving the tremendous majority of IQ differences between individuals to be explained genetically. Most scientists today believe that genes play a part in determining one's IQ. In spite of the high heritability of IQ, few genes have been found to have a significant impact on IQ. In other words, IQ is the invention of dealings between more than one gene.

Prenatal Factor

The researches have explored that birth complications and other factors happen during the time of birth can have severe effect on intelectual development. For instance, if the baby experiences lack of oxygen for a long drawn out of time during te birth delivery, the baby will have a high risk to brain damage and mental retardation.

Besides that, other aspect which biologically affect the IQ is the ratio of brain weight to body weight. Although physically the real brain weight has little or no effect to the person, but when evaluating the ratio of brain weight to body weight of different species, there is a correlation with the intelligence. The ratio calculated for humans is 1:50.

It has been projected that genetic engineering could be used to improve the level of intelligence of animals since intelligence appears to be at least partly dependent on brain structure and the genes shaping brain development.


Environment and intelligence are closely related to the human well-being. Thus, environmental factors play an important role in determining one's IQ. About 25% of the differences in people's IQ scores are related to the environmental factors. The factors that have been of greatest interest to scholars include prenatal development, nutrition, home and family environment, self-effort and health.

Prenatal development

Scientists have found many aspects during a woman's pregnancy that could influence a child's cognitive development including cigarette smoking and drinking during pregnancy. Cigarette smoking can be dangerous for the fetus and the newborn baby. Majority studies of pregnancies imply that the fetus and newborn are significantly affected by cigarette smoking during pregnancy. The baby will be born prematurely and tends to be lighter and smaller in all dimensions compared to the baby of non-smokers besides having some health problems.


Recent advances in nutritional neuroscience illustrate that particular nutrients have certain impacts on brain development which affect individual's intelligence. Experts said that short of certain vitamins and minerals in the diet can result in a lower IQ although there is enough food to eat. It is found that, many people are not growing in their full intelectual or physical potential due to such deficiencies. The reserches said that many local residents of poorer countries fail to get sufficient amount of nutrients in their normal diet have significant gaps in their IQ development. It is estimated that average IQ will increase radically if the consumption of iodine and other micronutrients are adequate.

Home and family environment

Many people believe that home and environment issue is one of the significant role in mental development and disparity in IQ. Studies put an evidence that all personality characteristics show that, environmental effects actually can bring about adoptive siblings or non-related children raised in different family. It is shown that the IQs of adoptive siblings, who have different genetic genes but sharing a familiar environment are correlated.


Self-effort is a very obvious factor for a person to develop their intelligence level especially in their schooling. This is based on individual's realization either they want to improve theirselves or remain the same. It is not the school quality that should be judged but the more important is regular school attendance, especially in elementary school. Besides that, those who are really paying attention in the class will have the opportunity to get better understanding in their studies. Usually, these students will easily voice out the qustions to their teachers if they have any difficulties in understanding the subjects studied either during the class period or not.


Another important factor is the individual's quality of health because one with a higher IQ have generally good health quality in means lower adult morbidity and mortality. Individual's who had psychological trauma resulting from a certain incident tends to have a severe nervousness syndrome called Posttraumatic stress disorder (PTSD) which are less dominant in higher intelligence bands.

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