To understand how scientists study the genetic and environmental factors that interact to produce variation in behavior across a population.
This is the second of two lessons about the field called behavioral genetics, in which scientists study the reciprocating influences of genes and environments on behavior, particularly human behavior.
Genes, Environments, and Behavior 1 provides students with a clear understanding of how behavior is defined by scientists and an overview of the genetic and environmental forces that interact to shape behavior.
Genes, Environments, and Behavior 2 introduces students to the various approaches scientists use to explore this interaction.
These lessons are based on the book, Behavioral Genetics: An introduction to how genes and environments interact through development to shape differences in mood, personality, and intelligence, published by AAAS and The Hastings Center. You may choose to print out chapters or order copies of the book. The PDFs and ordering information may be obtained at the Behavioral Genetics Project.
By the end of elementary school, students should be well aware of the fact that individuals differ in their behavior. They also should understand that behavior is shaped by several factors, and that some of these factors are under their own control, for example:
- They learn some behaviors (as opposed to the behaviors being instinctual)
- Some of their behavior is influenced by families, friends, classrooms, and cultures
- Memories and learned information shape what they attempt to do and what they avoid doing
- Through repetition and practice they can improve a behavior (such as a skill)
(Benchmarks for Science Literacy, p. 140.)
By the end of middle school, students should be aware that behavior is affected not only by the world around them—their experiences—but also by their own biology—their genetic inheritance. (Benchmarks for Science Literacy, p. 108.) They also should understand that while some animal species are limited to a repertoire of genetically determined behaviors, other species (including and especially the human species) have more complex brains and their possible range of behaviors is therefore broader. (Benchmarks for Science Literacy, p. 141.)
In high school, students should be ready to study the specific ways that the variables of genetics and experience contribute to behavior. High-school students should learn that the interaction is extraordinarily complex and contingent, that scientists study the relative effects of genes and environment using a variety of techniques, and that we still have a great deal to learn about the interactive influences on behavior. Finally, students should recognize that the range of any human individual’s possible behaviors is great and each person can shape his or her own life to a significant degree. (Benchmarks for Science Literacy, pp. 142, 153.)
An important objective of these lessons is to help students overcome the common public misperception that genes can have a direct relationship with behavior; for example, that there may be a “gene for criminality” or a “gene for religiosity.” Another common misperception that can be dispelled through these lessons is that the development of an organism is determined solely by genetic factors; this is called genetic determinism. Possibly the most important value of these lessons, therefore, is that they can help students understand why such beliefs are false.
This lesson is part of a group of lessons that focus on the social, behavioral, and economic sciences. These lessons are developed by AAAS and funded by the National Science Foundation Grant No. SES-0549096. For more lessons and activities that take a closer look at the social, behavioral, and economic sciences, be sure to check out the SBE Project page.
To engage students in the topic, have them use their Genes, Environments, and Behavior student esheet to go to and read the story, “Anja, an identical twin,” from Chapter 4: How is Genetic Research on Behavior Conducted?, published by AAAS and The Hastings Center. Students can read the story online via the student esheet, in books you have ordered, or on pages you have printed out. Alternatively, you or a student can read the story aloud. The story is less than a page long, so this should take just a few minutes.
- In what ways are Anja and her twin alike in terms of their behavior?
- In what ways do you behave similarly to your biological relatives?
- In what ways do you behave differently from your biological relatives?
- How do you think scientists study the factors that cause humans to vary in behavior?
Accept all responses and encourage students to give specific examples, from their own experience, of shared or unshared behaviors. The purpose of this activity is for students to begin to consider the challenges scientists face as they try to identify the specific genetic and environmental factors that influence behavior. Students probably will be able to at least name and possibly describe some of the research methods available to scientists. Allow 10 to 15 minutes for this activity.
In this part of the lesson, students will study how genetic research on behavior is conducted. To begin, have students use their student esheet to go to and read Chapter 4: How is Genetic Research on Behavior Conducted?
Then assign students to small groups. Have each group begin its work by looking at the section on Major Affective Disorders from Online Mendelian Inheritance in Man. Students may wish initially to scan this document on the Web—noticing in particular the length of the research summary, which is 12 pages long exclusive of references—but they need to print out the first five pages or receive a printed copy of those pages from you.
Explain that “Major Affective Disorder” is a scientific synonym for what the general public often refers to as manic-depressive illness or bipolar disease. Tell students that this is a resource for working scientists and you do NOT expect them to understand much at all of this document. However, you do expect them to obtain from it a sense of the depth and variety of research that scientists put into one single behavioral trait.
Instruct students to conduct a scavenger hunt for, and mark with a highlighter, phrases that reference research methods including:
- Family studies (including twin and adoption)
- Molecular studies
- Brain imaging studies
You should refer to the Scavenger Hunt Tip Sheet when conducting this activity.
When groups have finished this first scavenger hunt, ask them to report on the phrases they found and their overall reaction to the resource.
Then ask them to conduct additional scavenger hunts (using different colored highlighters) for:
- Locations mentioned where genetic research into Major Affective Disorder has been studied
- Use of the word “suggested” and other qualifying, non-definitive phrases to describe study findings
- Use of phrases that suggest a disconfirmed hypothesis (focus this search on p. 4)
Conclude with a discussion prompted by this question:
- What does this resource tell you about the scientific process as applied in the field of behavioral genetics? (Scientists from all over the world contribute evidence on the question of the role genes play [within environments] to affect behavior. They use a variety of research methods, confirming and disconfirming previous findings, to build a body of knowledge.)
Ask students, in class and/or as homework, to write a brief essay focusing on one particular behavioral trait (for example: altruism, intelligence, risk-taking) and suggesting how it might be researched through:
- Animal studies
- Family studies
- Genetic studies
- Brain imaging studies
The Image Archive on the American Eugenics Movement, produced by Cold Harbor Laboratory Dolan DNA Learning Center, will give students insight into early methods used by scientists to study behavioral traits. It candidly portrays the flaws in that research and the ramifications when flawed research is applied to social policy such as immigration and sterilization laws. If students have limited time, encourage them to focus on the exhibits: “Research Methods” and “Research Flaws.”