Behavioral Genetics: Definition, And Its 5 Most Important Findings

Behavioral genetics

Behavioral genetics is a science that studies how our genes influence behavior and in the development of our psychological and behavioral traits.

Through comparative studies with twins and adopted children, experts in this scientific field strive to understand the genetic mechanisms involved in behavior and various diseases.

In this article we explain what behavioral genetics is and what it studies, what its historical background is, its study methods and the main findings that have emerged from this scientific discipline.

Behavioral genetics: what is it and what does it study?

Behavioral genetics, also called behavioral genetics, It is a scientific discipline that is responsible for studying the influence of genetic composition on behavior and the interaction between heredity and the environment as they affect behavior.

Today we know that the vast majority of behaviors studied in psychology are affected by the particular genetics of the individual in question, so it is not so much interesting to know whether genes are important or not, but rather to study to what extent they affect a specific behavior.

In this sense, behavioral genetics tries to answer questions such as: How do genes and environment interact to influence behaviors? What specific genes are responsible? What is your mecanism of action? The field of this discipline is advancing rapidly, since we increasingly have better technological means to observe and study in depth the genes involved in each behavior.

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Historical background

Behavioral genetics or, at least, the study of the relationship between behavior and genetics, has been the subject of interest of numerous researchers since the end of the 19th century.

It was the English polymath, Francis Galton (cousin of Charles Darwin), who pioneered research with twins and the use of many of the statistical methods of analysis that are currently used. This scientist carried out the first systematic studies with families, demonstrating how certain behavioral traits could be transmitted and inherited from parents to children.

In the 1960s, various publications based on twin and adoption studies put on the table the importance of genetic factors in relation to intelligence quotient and some psychiatric pathologies such as schizophrenia. The controversy that arose as a result of articles published by psychologist Arthur Jensen, who suggested that differences in intelligence were mediated by race, also served as an incentive for behavioral genetics to continue developing as a discipline.

After the most controversial years, the discipline went from studying racial differences to focusing on the influence of genetic factors on individual differences based on constructs such as personality, cognitive abilities or psychopathology. Already in the 1980s, behavioral genetics was established as a full-fledged scientific discipline, and the scientific community supported the importance of heredity in explaining intelligence levels, measured with an indicator such as IQ.

Currently, scientific research related to behavioral genetics is becoming more and more abundantthanks to the work of a multitude of scientists coordinated in projects such as the Human Genome Project, in which for fifteen years the sequence of chemical base pairs that make up DNA was investigated and nearly 25,000 genes in the human genome were identified.

Robert Plomin, one of the most prominent geneticists, has suggested that in the coming years the genes responsible for the heritability of behavior will be identified and we will be able to begin to trace the routes from genes to the brain, and from the brain to behavior. Furthermore, the scientist insists that behavioral genetics is the scientific discipline that best interprets the importance of the environment when explaining individual differences.

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Study methods

In behavioral genetics, quantitative genetic methods are used to estimate the net effect of genetic and environmental factors on individual differences. in any complex trait, including behavioral traits. Additionally, molecular genetic methods are used to identify the specific genes that are responsible for a given genetic influence.

The research is carried out on both animals and humans; However, studies using animal models tend to provide more precise data than research conducted in humans, since both genes and the environment can be manipulated and controlled in the laboratory.

Due to the impossibility of manipulating genes and the environment in human research, two quasi-experimental methods are usually used to detect genetic influence on individual differences in behavioral traits; the twin method, based on the comparison of monozygotic twins (they are genetically identical to each other and come from the same egg) and dizygotic twins (they developed from two eggs fertilized at the same time).

In twin studies, if monozygotic twins are significantly more similar than dizygotic twins, it means that genes play a determining role in the behavioral trait; That is, to the extent that behavioral variability is caused by environmental factors, dizygotic twins should be as similar for the trait in question as monozygotic twins, since both types of twins are raised by the same parents in the same location. and at the same time. . Another study method is adoption, in which a quasi-experimental design is carried out based on the fact that adopted children are separated early from their biological parents, making it possible to study the separate effects of nature and nurture. One of the most notable studies was carried out in 1966 by geneticist Leonard Heston, demonstrating that children adopted away from their biological schizophrenic mothers had the same chance of developing the disease (about 10%) as children raised by their mothers. biological with schizophrenia.

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Main scientific findings

By using genetically sensitive designs, such as twin studies or adoption studies, Research in behavioral genetics has generated various scientific findings over the years. The main discoveries are presented below.

1. All psychological traits show significant genetic influence

Psychological traits have consistently shown a significant genetic influence in studies, which has led to the description of the first “law” of behavioral genetics.

2. There is no 100% heritable trait

Although heritability estimates are significantly greater than 0%, are also significantly less than 100%. Heritability percentages are important, generally between 30-50%, but very far from 100%.

3. Heritability is caused by the small effect of many genes

Scientific studies show that many genes affect complex traits, as with behavior. If only a few genes were responsible for the heritability of a trait, the selected lines would separate after a few generations and would not diverge further in subsequent generations.

4. The heritability of intelligence increases throughout development

Numerous investigations have proven that the heritability of intelligence (consistently for more than three decades) increases linearly throughout life. A finding made in longitudinal and cross-sectional analyses, as well as in adoption and twin studies.

5. Most environmental effects are not shared by children growing up in the same family.

Although, a priori, it might seem that growing up in the same family makes siblings psychologically similar, the truth is that in most dimensions of behavior and in the development of psychological disorders, it is genetics that is responsible for the similarity between siblings.

Although environmental effects can have an important influence, they do not cause siblings who grow up in the same family to be similar in their behavioral traits.

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