A major portion of the preceding chapter was devoted to potential threats to internal and external validity of research. The present chapter also deals with this broad topic, except that the focus is on artifacts and pitfalls emanating from the participants (i.e., researcher and subject). We realize that you may think that we dwell too much on things that may go wrong in sociobehavioral research. Yet becoming aware of what may go wrong is essential for planning and execution of research as well as for interpretation of results, be they one's own or those of others.