Assignment: Interpreting Brain Research
Assignment: How Interpreting the Results of Brain Research
1.7 Interpreting the Results of Brain Research
When psychologists conduct research, they study qualities or characteristics of organisms that vary. Variable is the name that psychologists give to an element of behavior that is not constant. That is, psychologists study variables associated with behavior, such as age, intelligence, education, or personality. Physiological psychologists study biological variables associated with behavior, such as brain function or brain chemistry. They begin with a hypothesis, or a testable prediction about the relationship between two or more variables, and design a research project that permits them to test whether the predicted relationship between the two variables really exists. For example, in the microdialysis study of sexual behavior in quails (described in the previ- ous section), the investigators examined the relationship between the brain chemical dopamine and sex drive in male quails.
Psychological research can be grouped into two categories: experimental research and nonex- perimental research. Experimental research involves conducting experiments in which behavior is measured while one or more variables are manipulated and all other variables are held constant or controlled. A variable that is manipulated in an experiment is called an independent variable. In an experiment, the concept of control is most important. All environmental and individual vari- ables (such as room temperature, time of day, or medication level) are strictly controlled in an experiment, and only the independent variables are allowed to vary. One way that psychologists do that is to randomly assign participants to groups. One group, called the experimental group, receives the independent variable, and the other group, called the control group, does not receive the independent variable. By holding the other variables constant while the independent variable is manipulated, we can be certain that only the independent variable is causing any change in the behavior that is observed.
Sometimes psychologists cannot control the variables they want to study. For example, if a psy- chologist was interested in studying the effect of being orphaned on performance in school, that researcher could not randomly assign children to an experimental group and then kill their par- ents, which would be required in an experiment. Children come to the psychology lab with or without a history of parental loss, and their parental status cannot be controlled. In these situa- tions where variables cannot be controlled, psychologists have to use another research strategy, called nonexperimental research.
Nonexperimental research involves collecting data on particular variables without controlling any of the variables. One form of nonexperimental research is called correlational research. Correlational research involves studying the relationship between two or more variables. When conducting correlational research, the psychologist measures one or more variables of interest (for example, age, sex, and a behavioral measure of interest) without trying to control any of the variables. The variables studied in correlational studies already exist and are not manipulated by the researcher. Thus, correlational research cannot tell us about the cause of a behavior but can inform us about the co-occurrence of the variables.
Physiological psychologists conduct experiments using brain lesioning and brain stimulation tech- niques. The investigators manipulate the brain by lesioning or stimulating it in order to study the effects of the manipulation on behavior, while holding all other variables constant. In a brain
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