Chapter 2: Behavioral Analysis of Drug Effects
Chapter 2 begins by contextualizing the emergence of behavioral pharmacology as a distinct field of study. Thereafter,
students are provided with key concepts in research design and behavioral psychology that are important for
understanding how drug effects are measured. Particular attention is paid to experimental control, placebo effects, and
designs commonly used in drug research. In addition, the chapter describes how drug effects can be assessed using
specific tests of unconditioned as well as classically and operantly conditioned behaviors in research animals. Measures
of drug effects on human behaviors, including abuse liability, are also reviewed. These behavioral paradigms will, in later
chapters, be frequently revisited in the course of studying the effects of specific classes of drugs.
Behavioral pharmacology is the study of the effects of drugs on behavior. The behavioral pharmacologist uses
experimental techniques of modern behaviorally oriented psychology and behavioral neuroscience to also examine
the mechanisms that underlie drug effects.
For millennia, scholars and writers have produced anecdotal accounts of the effects of drugs on humans. Yet,
rigorous scientific investigation of drug effects began little more than a century ago, propelled by the advent of
chemical techniques and the development of objective and systematic methods for studying behavior.
The emergence of behavioral pharmacology as a separate discipline was largely propelled by three events: (1) the
therapeutic and commercial success of antipsychotic drugs, particularly chlorpromazine, which sparked a need for
laboratory tests useful in examining the therapeutic effects of such drugs; (2) evidence of the usefulness of operant
techniques in studying drug effects; (3) the application of physiology to the understanding of behavior and drug
Scientific experimentation entails a search for causal relationships between events.
Scientific experiments contain an independent variable that is manipulated by a researcher and a dependent
variable that is measured. In most experimental research studies conducted by behavioral pharmacologists, the
independent variable is the presence or concentration of a drug in the body, and the dependent variable is some
aspect of behavior.
Behavioral pharmacology studies may use a within-subjects design, in which a participant’s behavior is compared
across drugged and drug-free states, or a between-subjects design, in which drugged participants’ behavior is
compared to that of drug-free participants.
The treatment of participants in the control group in an experiment should be as similar as possible to the treatment
of participants in the experimental group. For this reason, control-group participants are usually administered a
placebo: an inactive substance given in exactly the same way as the drug of interest. This procedure controls for
changes in behavior that might result due to the placebo effect.
The placebo effect refers to the observation that when people expect to experience a drug effect, they often
demonstrate that effect even if they are administered only a chemically inert substance.
When an investigational drug is being tested for its therapeutic effects, it is standard to use the three-groups design:
one group is given the investigational drug, one group is given a placebo, and one group is given an established drug
with known therapeutic effect.
A double-blind procedure, in which neither the researchers nor the participants are informed as to which group they
are in, is used to eliminate the effect of experimenter bias.
Nonexperimental drug research can illustrate relationships between events but cannot definitely establish the
existence of a cause–effect relationship.