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 adopted twins and children, experts in this scientific field strive to understand the genetic mechanisms involved in behavior and in various diseases.
In this article, we explain what behavioral genetics is and what it studies, what is its historical background, 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, is a scientific discipline responsible for studying the influence of genetic makeup on behavior and the interaction between heredity and the environment to the extent that 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 a question of whether the genes are important or not, but rather of studying to what extent they affect a specific behavior.
In this sense, behavioral genetics seeks to answer questions such as: How do genes and the environment interact to influence behavior? What specific genes are responsible? What is its mechanism of action? The field of this discipline is evolving rapidly, as we increasingly have better technological means to observe and study in depth the genes involved in each behavior.
Behavioral genetics, or at least the study of the relationship between behavior and genetics, has interested many researchers since the late 19th century.
He was the English polymath Francis Galton (cousin of Charles Darwin), the pioneer of twin research and the use of many statistical methods of analysis currently in use. This scientist conducted the first systematic studies with families, demonstrating how certain behavioral traits could be transmitted and inherited from parents to children.
In the 1960s, several publications based on studies of twins and adoption put on the table the importance of genetic factors in relation to IQ and certain psychiatric pathologies such as schizophrenia. The controversy that arose from articles published by psychologist Arthur Jensen, which suggested that differences in intelligence were mediated by race, also prompted behavioral genetics to continue to develop as a discipline.
After the most controversial years, the discipline shifted 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. As early as the 1980s, behavioral genetics was established as a scientific discipline in its own right, and the scientific community has supported the importance of inheritance in explaining levels of intelligence, as measured by an indicator such as IQ.
Currently, scientific research related to behavioral genetics is increasingly abundantThanks to the work of many 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 has been studied and nearly 25,000 genes in the human genome.
Robert Plomin, one of the most prominent geneticists, suggested that in the years to come, the genes responsible for the heritability of behavior will be identified and that we can begin to trace the pathways from genes to brain and from brain to brain. . conduct. In addition, the scientist insists that behavioral genetics is the scientific discipline that best interprets the importance of the environment in explaining individual differences.
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. In addition, molecular genetic methods are used to identify specific genes responsible for a particular genetic influence.
Research is conducted in both animals and humans; however, studies using animal models tend to provide more accurate data than research in humans, because genes and the environment can be manipulated and controlled in the laboratory.
Due to the inability to manipulate genes and the environment in research with humans, two quasi-experimental methods are often used to detect genetic influence on individual differences in behavioral traits; the twins method, based on the comparison of monozygotic (they are genetically identical and come from the same egg) and dizygotic (they were developed from two eggs fertilized at the same time) twins.
In studies of twins, if these are monozygous, they are significantly more similar than dicygotics meaning that genes play a determining role in the behavioral trait; that is, since behavior variability is caused by environmental factors, dizygotic twins should be as similar to the trait in question as monozygotic twins, because both types of twins are raised by the same parents in the same place and at the same time. . Another method of study is adoption, in which a quasi-experimental design is carried out on the basis of which adopted children are soon separated from their biological parents, so it is possible to study the effects separately from nature and of parenthood. One of the most important studies was conducted in 1966 by geneticist Leonard Heston, showing that children adopted far from their biological schizophrenic mothers had the same chances of developing the disease (around 10%) as children raised by their mothers. biological patients with schizophrenia.
Main scientific discoveries
Using genetically sensitive designs, such as twin studies or adoption studies, research in behavioral genetics has generated several scientific discoveries over the years. The main findings are presented below.
1. All psychological traits show significant genetic influence
Psychological traits have consistently shown a significant genetic influence in the studies performed, which led to the description of the first “law” of behavioral genetics.
2. There is no 100% hereditary trait
Although the heritability estimates are well above 0%, they are also significantly less than 100%. The percentages of heritability are important, generally between 30 and 50%, but far from 100%.
3. Heritability is caused by the weak effect of many genes
Scientific studies show that many genes affect complex traits, As for behavior. If only a few genes were responsible for the heritability of a trait, the selected lines would split off after a few generations and would not diverge further in subsequent generations.
4. The heritability of intelligence increases throughout development
Numerous studies have shown that the heritability of intelligence (Consistently for more than three decades) increases linearly throughout life. A finding made in longitudinal and cross-sectional analyzes, as well as in adoption and twin studies.
5. Most of the effects on the environment are not shared by children growing up in the same family.
Although, at first glance, it may 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, genetics is responsible for the similarity between brothers.
While environmental effects can have a significant influence, they do not cause siblings growing up in the same family to have similar behavioral traits.
Gómez, P. (1995). The genetic determination of human behavior. A critical review of the philosophy and genetics of behavior.
Plomin, R. 1990. Nature and food. An introduction to the genetics of human behavior. Pacific Grove, CA, Brooks / Cole Publishing Company
Plomin, R., DeFries, JC, McClearn, GE, Pezzi, L. and Flores, EA (1984). Behavioral genetics. Editorial alliance.