ABSTRACT
This chapter underscores the increasing importance of understanding the effects of environmental factors in evaluating physiological responses of the behaving person. Most of the relevant environmental factors are internal (e.g., drugs, hormones) whereas a few are external (e.g., illumination). It is important to know about these effects not only for human welfare, but to consider them as possible influences in the conduct of research. Certain commonly used substances-such as coffee, tea, soft drinks, alcohol, nicotine, and prescribed and nonprescribed medications--can affect interpretations of psychophysiological data. Thus, investigators must be aware of these possible effects when carrying out studies in psychophysiology. Researchers can control for unwanted influences by asking participants to abstain from using certain substances for a suitable length of time before taking part in an experiment.
