Heritability Factor Of Intelligence

Historically, Intelligence has always been looked up to as a stable and fixed trait of an individual. Only a few researchers claimed that intelligence is highly heritable and few claimed it to be highly no heritable. While the majority of the psychologists and researchers took the midway approach and claimed intelligence to be a mixture of both nature and nurture.

Most researchers have included the study of identical twins in order to check the heritability factor of intelligence. They have mostly studied the twins who were raised apart from one another from early childhood. The goal of such studies was to highlight the differences that identical twins had, due to the difference in environment and difference of parents.

If the twins are separated from one another and are dispersed randomly in the environment, they will still be having the same genes but the environment in which they are brought up would be different from one another. Their environment would have nothing in common except in the case of some environmental overlap. Know that every environment is unique and has separate patterns and structures.

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If both the twins are brought up in different environments and are asked to take IQ tests (e.g. https://iq-global-test.com/) in order to test intelligence level, the correlation of their performances in the tests and their IQ scores would decide the link between intelligence and heredity.

Another method used to test the heritability factor of intelligence is to measure the difference between the IQ scores of identical twins with the IQ scores of fraternal twins. But the important point to consider here is that only those aspects of intelligence are taken that are present in the IQ test being selected so the IQ scores represent only those aspects of intelligence that are present in the test.

Research Findings On Heritability of Intelligence

The research studies on identical twins showed that the correlation among the scores of the twins raised apart is strong. They are highly correlated even after being raised apart from one another. In fact, when the IQ score of a kid was compared with the IQ score of a biological parent and the IQ score of an adoptive parent, it was highly correlated with the IQ level of a biological parent as compared to the IQ level of the adoptive parent.

There are also significant findings that heritability factors differ between different racial and ethnic groups. Heritability factors also differ between the same groups over a period of time. It highlighted that the debate of genes versus environment depends on some other factors as well such as the socioeconomic status of the individual.

The psychologist Robert Plomin also highlighted that with the passage of time the heritability factors of intelligence increase among the individual. That means as the person grows older genetic factors become the more prominent determinants of intelligence while the environmental factors become less prominent determinants of intelligence.

It is also seen that the IQ scores around the world have increased rapidly since the 20th century. Many psychologists have claimed that this increase in IQ scores around the world is the addition of Vitamin C in the diet of mothers giving birth to children. Vitamin C has now become an essential component of prenatal and postnatal diets. In the past, the nutritional intake of mothers, as well as infants, was not good as it is improved now.

Richard Herrnstein and Charles Murray claimed that the IQ scores depict the individual’s success in life and this life success can depend on differences among racial groups and these differences can be due to heredity. But, such claims are hypothetical in nature.

Looking at the curves of IQ scores among various countries and regions showed that IQ scores differ among various socioeconomic groups. The better the socioeconomic status the better the IQ score. But the psychologists have mixed views regarding the cause of such differences. Many researchers claim that the learning facilities and education, no doubt, play a major role in influencing the intelligence of the being. While some claim that this difference is due to hereditary factors.

The differences are based on the IQ level and not on intelligence which is a broad concept and includes various other factors. That is why there is no broad agreement on the causes of such differences.

The research shows that no matter how much heritable the intelligence may get there are still some factors that are technical in this regard. Even the heritable factors get modified when they are intervened. There are several training programs available around the world that teach the tips and tricks to increase the intelligence level. Such training provides the guidance to boost the intellectual skills required for a person to become intelligent.

Know that, no training program or any sort of environmental condition can take away the intelligence of a person. An intelligent individual will remain intelligent no matter what the conditions are. But with proper training, the intellectual skills can be increased.


One thing that needs to be kept in mind is that intelligence is not a conclusion that can be made the day when a child is born. No doubt, heredity plays a major role in influencing the intelligence of a being but no one can deny the impact of interventions that can be made in order to boost the intelligence level.

It is important to test the performance of training functions and how they play a role in influencing the intelligence level of an individual. A person is a product of his or her genetic makeup and the environmental conditions in which he or she lives.

Life is an ongoing journey of learning and unlearning. The level of intelligence can also be increased or decreased depending upon the approach that we take.

Intelligence was historically be seen as a fixed trait but now psychologists have established that it changes over time. The causes behind the change of intelligence are still under debate and there is a long way for the researchers to cover.

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