Genetics is the study of genes and the variation of characteristics that are influenced by genes—including physical and psychological characteristics. All human traits, from one's height to one's fear of heights , are driven by a complex interplay between the expression of inherited genes and feedback from the environment .
Why Genes Matter in Psychology
Genes help to define who an individual is inside and out. While non-genetic factors have a role to play, too, what scientists have learned about these influences can clash with common wisdom . A characteristic or behavior that appears to result from a child’s upbringing—such as a proneness to mental illness or divorce — may actually be largely a product of the genes she inherited from her parents. In fact, research investigating the influence of the family environment suggests that it accounts for a surprisingly small amount of the difference between people on characteristics that scientists measure.
A gene is the basic unit through which genetic information is stored and passed between generations. Physically, a gene is a specific section of one of the long, double-helix-shaped DNA molecules that appear in each cell of the body. Genes vary in size, comprising anywhere from hundreds to millions of the nucleotides that collectively make up DNA. Many (but not all) genes provide chemical “instructions” for the creation of protein molecules, or serve other roles that are integral to the function of an organism. Different versions of the same gene are called alleles.
The genome is the entirety of the genetic material contained in an individual. Human DNA is estimated to contain between 20,000 and 25,000 genes. The vast majority of each person’s genome is identical to that of the next person, but the portion that differs is consequential for how individuals develop.
A chromosome is a structure within a cell nucleus that is made up of a long DNA molecule and proteins that provide support. Each human cell contains 23 pairs of chromosomes, which together store a person’s genetic code.
The Science of Genetics and Behavior
It may seem obvious that the genes people inherit from their parents and share with their siblings have an effect on behavior and temperament. Individuals are often noticeably more similar in a variety of ways to immediate family members than they are to more distant ones, or to non-relatives. Of course, there are plenty of notable differences within families as well. Scientists have employed an array of methods to drill down into how and to what extent genetic differences truly account for psychological differences.
Behavioral genetics, or behavior genetics, is the study of psychological differences between individuals and how genetic and non-genetic factors create those differences. Among other questions, behavioral genetics researchers have sought to determine the extent to which various specific differences in people’s behaviors and traits can be explained by differences in their genetic code.
Scientists use specialized methods to explore the links between genes and individual differences. Studies of twins who either do or do not have identical genomes allow for estimates of the degree to which genes drive the variation in psychological traits. Other methods, such as studying adopted children and their adoptive and biological parents, have been used as well. In recent years, genome-wide association studies (GWAS) have emerged as a major approach in behavioral genetics. A GWAS uses genetic testing to identify numerous genetic differences across many individuals , then analyze the association between these differences and personality traits or other outcomes.
Heritability is a measure of how much of the differences between people on a given characteristic can be attributed to genetics. More specifically, it is an estimate of the amount of variation between individuals in a given population that can be accounted for by genetic differences. Behavioral genetics research indicates that every trait is (at least) a little bit heritable —though the fact that a trait is heritable does not mean it is fixed.
Explore More About Genetics
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