What do the following classic studies have in common?

• Stanley Milgram found that about two thirds of his research participants were willing to administer dangerous shocks to another person just because they were told to by an authority figure (Milgram, 1963)^[1].
• Elizabeth Loftus and Jacqueline Pickrell showed that it is relatively easy to “implant” false memories in people by repeatedly asking them about childhood events that did not actually happen to them (Loftus & Pickrell, 1995)^[2].
• John Cacioppo and Richard Petty evaluated the validity of their Need for Cognition Scale—a measure of the extent to which people like and value thinking—by comparing the scores of university professors with those of factory workers (Cacioppo & Petty, 1982)^[3].
• David Rosenhan found that confederates who went to psychiatric hospitals claiming to have heard voices saying things like “empty” and “thud” were labeled as schizophrenic by the hospital staff and kept there even though they behaved normally in all other ways (Rosenhan, 1973)^[4].

The answer for purposes of this chapter is that they are not experiments. In this chapter we look more closely at non-experimental research. We begin with a general definition of , non-experimental research, along with a discussion of when and why non-experimental research is more appropriate than experimental research. We then look separately at three important types of non-experimental research: cross-sectional research, correlational research and observational research.