Are the most intelligent people by genetic inheritance?

Everyone has ever wondered if the most intelligent people are by genetic inheritance or because of the environmental influences they receive, such as the quality of nutrition or the education provided by parents. In recent years, behavior genetics has managed to answer this historical question in detail.

Research in the field of differential psychology reveals that both genes and environment have a very significant weight in determining the intelligence quotient, the classic measure of intelligence. However, the relevance of heredity seems to be slightly higher than that of environment.

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How is intelligence defined?

The construct "intelligence" is difficult to delimit, since multiple meanings have been attributed to it both in the lay language and from the scientific community. It is a complex capacity that encompasses the ability to learn new information, to apply different types of reasoning and to solve problems, among many others.

A special definition is the one that has been made from the operational approach. This perspective proposes that intelligence should be defined as

“what is measured by IQ tests”, instruments that have been shown to be moderately useful for predicting aspects such as job performance and socioeconomic status.

However, intelligence is a very broad attribute and it does not only exist in human beings. It has been defined by many authors as the ability to behave adaptively in complex situations in order to reach a goal; In this type of definition, the conception of intelligence as a global and stable factor stands out.

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Relationship between genetics and intelligence

From the field of behavior genetics, which analyzes individual differences in behavioral aspects (such as intelligence) based on genetic methods, it is estimated that the heritability coefficient of IQ ranges from 0.40 and 0.70. This means that about half of the variability is explained by heritable factors.

Based on reviews of studies of this type, Antonio Andrés Pueyo concludes that approximately 50% of the variance in intelligence remains explained by causes of genetic origin, while the other 50% is due to different environmental factors and random errors of measurement.

In general, the oldest studies have found a greater weight of genetic inheritance in intelligence than recent research. It also seems that the heritability coefficient is higher in cases where the IQ is very high (more than 125) or very low (less than 75).

Regarding the different factors that make up intelligence, some studies have found that verbal skills are inherited to a greater extent than those of the manipulative type. The weight of genetics in verbal IQ increases with age; the same is true of other components of intelligence, although not as noticeably.

On the other hand, the fluid intelligence described by Raymond B. Cattell, a construct similar to the global factor ("g") originally used by pioneer Charles Spearman, is more influenced by genetic inheritance than crystallized intelligence. While the first is associated with reasoning and solving new problems, the second refers to accumulated knowledge

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Influence of brain structure and processes

Different authors have pointed out the relevance of the physiological processes of the central nervous system in intelligence. In this sense, structures and functions would be involved such as the frontal lobes, the density of gray matter (composed of cell bodies, unmyelinated dendrites, and glia) in the brain or the metabolic rate of glucose.

Thus, Vernon wrote that the differences found in the IQ tests reflect a greater speed and efficiency in the transmission of nerve impulses, while according to Eysenck the most important thing is the number of errors in these connections: if there are fewer transmission failures, the brain will consume less glucose, reducing energy effort.

Other studies have linked measures of intelligence to blood flow and neurochemical activity in the brain. frontal lobes, as well as the density of the Gray matter. All these morphological and functional characteristics are inherited to a significant degree, since they depend on the expression of certain genes.

Environmental Factors Affecting IQ

Intelligence depends to a large extent on the environment. In this sense, a large number of factors are relevant, among which are access to quality nutrition, education and healthcare that allow the greatest possible development of the biological potential of the brain of each person.

In many cases it is extremely difficult to determine what proportion of behavioral variability can be attribute to heredity and which to the environment, particularly when we talk about the influences related to the family environment immediate. There is also a reciprocal interaction between genetics and the environment that occurs constantly.

According to Andrés Pueyo, environmental factors explain almost half of the variance in intelligence, a weight very similar to that of genes. Within 50% of variability that is not justified by heredity he attributes 30% to the common or interfamily variance and 10% to the non-shared environment. The error variance weights another 10% for this author.

Thus, non-shared environmental influences, which differ between people raised in the same family, seem to be more relevant in the determination of intelligence than the shared environment, although its weight is high enough to be taken into account. consideration.