Over the first two-thirds of the 20th century, deception became a staple of psychological research. According to a recent history of deception in social psychology, before 1950 only about 10 percent of articles in social psychology journals involved deceptive methods. By the 1970s, the use of deception had reached over 50 percent, and in some journals the figure reached two-thirds of studies. This means that subjects in social psychology experiments -- at least those that survived the peer-review process and made it to publication -- had a better than 50-50 chance of having the truth withheld from them, being told things that were not true, or being manipulated in covert ways.
Proponents of deception argue that they are using little lies in order to uncover large truths. Many subjects voice no objection, and sophisticated ethical defenses of the practice are readily provided. In a perfect world, perhaps, deception would be scrupulously avoided, but ours is not perfect, so proponents argue that compromises must be made. Of course, they admit, researchers should do their best to avoid deception wherever possible, employing it only as a last resort. In some cases, it may be possible to develop alternative methodologies that do not require it. In the end, however, deception is an indispensable tool in the pursuit of knowledge.
The American Psychological Association gives explicit support to the argument that dishonesty is necessary for scientific progress. The view that the ends justify the means in apparent in the APA's Ethical Principles of Psychologists and Code of Conduct, which reads as follows: "Psychologists do not conduct a study involving deception unless they have determined that the use of deceptive techniques is justified by the study's significant prospective scientific, educational or applied value and that effective non-deceptive alternatives are not feasible." Moreover, the APA code explicitly forbids the use of deception in research that is reasonably expected to cause "physical pain or severe emotional distress." The implication seems to be that deception by itself is not harmful or objectionable.
Psychology is the nation's second most common undergraduate major, numbering around 90,000 students since the mid-2000s. Permissive attitudes toward deception permeate many introductory psychology courses. To receive a passing grade, students are often required to serve as subjects in several psychological studies, like the one described above. In the beginning, many students have no idea that they may be deceived by researchers, teachers, and fellow students. As the course progresses, they learn that many of the best-known psychological experiments of the 20th century were founded on deceptions of one kind or another. By the end of the semester, students may be convinced that deception is a legitimate technique.