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  • Malkiat Singh Duhra

Importance of IQ (Intelligence Quotient)

Updated: Jan 23, 2022




Intelligence Quotient ( I Q ) is determined by a number of factors which include both genetic as well as non-genetic factors. Even though genetic factors play the major role in the determining of I Q , various other modifiable environmental influences can influence the I Q of an individual. The I Q of an individual is multifactorial and is determined by a multitude of factors. Even though genetic susceptibility plays a crucial role on the I Q of the individual, various modifiable environmental factors like education, premature birth, nutrition, pollution, drug, and alcohol abuse, mental illness, and diseases can have an influence on an individual’s I Q . These modifiable factors can reinforce or weaken genetic susceptibility.


There has been significant controversy in the academic community about the heritability of I Q since research on the issue began in the late nineteenth century. Intelligence in the normal range is a polygenic trait ( influenced more than one gene ), and is influenced by more than 500 genes. Similarly, in I Q of closely related persons requires careful study because environmental factors may be correlated with genetic factors. Early twin studies of adult individuals have found a heritability of I Q between 57 percent and 73 percent, with the most recent studies showing heritability for I Q as high as 80 percent. The heritability of I Q increases with age and reaches an asymptote at 18-20 years of age and continues at that level well into adulthood. However, poor prenatal environment, malnutrition, and diseases are known to have lifelong deleterious effects.


Evidence of genetic influences and environmental influences in I Q is mentioned below.

  1. Twins studies show that identical twins I Q’s are more similar than those of fraternal twins.

  2. Siblings reared together in the same home have I Q that are more similar than those of adopted children raised together in the same environment.

  3. Identical twins reared apart have I Q’s that are less similar than identical twins reared in the same environment.


Although I Q differences between individuals have been shown to have a large hereditary component, it does not follow that mean group-level disparities ( between group differences ) in I Q have a genetic basis. The scientific consensus is that there is no evidence for a genetic component behind I Q differences between racial groups. A study in 2006 found that adult height has a heritability estimated at 0.8 when looking only at the height at the variation within families where the environment should be similar. Other traits have lower heritability which indicates a relatively larger environmental influence. For example, a twin study on the heritability of depression in men calculated it as 0.29 while it was 0.42 for women in the same study. The heritability measures in infancy are as low as 0.2, in middle age 0.4, and in adulthood as high as 0.8. The brain undergoes morphological changes in development which suggests that age-related physical changes could also contribute to this effect.


Intelligence is determined by both your environment and your genes. There are a lot of things you can do to make sure your brain is always at its best, but nobody can deny that the genes you were born with make a difference too. Research into genetics has become amazingly advanced in recent years, and a new study has identified 22 genes involved in intelligence. A gene being statistically associated with intelligence does not mean it is solely responsible for how well you will do on an I Q test. A lot of other factors comes into play, and gene is only one. So there is still a lot of other stuff contributing to intelligence aside from genes including upbringing, lifestyle, and even technology.


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