Behavioral Genetics
Learning Outcomes
- Describe the interaction between genetics and the environment
- Compare monozygotic and dizygotic twins
Behavioral geneticists study how individual differences arise, in the present, through the interaction of genes and the environment. When studying human behavior, behavioral geneticists often employ twin and adoption studies to research questions of interest. Twin studies compare the rates that a given behavioral trait is shared among identical and fraternal twins; adoption studies compare those rates among biologically related relatives and adopted relatives. Both approaches provide some insight into the relative importance of genes and environment for the expression of a given trait.
Nature or Nurture?
For decades, scholars have carried on the “nature/nurture” debate. For any particular feature, those on the “nature” side would argue that heredity plays the most important role in bringing about that feature. Those on the “nurture” side would argue that one’s environment is most significant in shaping the way we are. This debate continues in questions about what makes us masculine or feminine (Lippa, 2002), concerns about vision (Mutti, Kadnik, & Adams, 1996), and many other developmental issues.
Most scholars agree that there is a constant interplay between the two forces. It is difficult to isolate the root of any single behavior as a result solely of nature or nurture, and most scholars believe that even determining the extent to which nature or nurture impacts a human feature is difficult to answer. In fact, almost all human features are polygenic (a result of many genes) and multifactorial (a result of many factors, both genetic and environmental). It is as if one’s genetic make-up sets up a range of possibilities, which may or may not be realized depending upon one’s environmental experiences. For instance, a person might be genetically predisposed to develop diabetes, but the person’s lifestyle may help bring about the disease.
When you think about your own family history, it is easy to see that there are certain personality traits, behavioral characteristics, and medical conditions that are more common than others. This is the reason that doctors ask you about your family medical history. While genetic predisposition is important to consider, there are some family members who, for a variety of reasons, seemed to defy the odds of developing these conditions. These differences can be explained in part by the effect of epigenetic (above the genome) changes.
Watch It
This video explains some of the research that gives insights into the complicated relationship between nature and nurture.
You can view the transcript for “Epigenetics: Nature vs nurture” here (opens in new window).
The Epigenetic Framework
The term “epigenetic” has been used in developmental psychology to describe psychological development as the result of an ongoing, bi-directional interchange between heredity and the environment. Gott