To a graduate student in a program of experimental social psychology in the 1960s, few studies were more significant than Robert Rosenthal's (1966, 1967) analysis of the effects of experimenter expectations in psychological research. It was a revelation: The responses of subjects to carefully defined and manipulated variables could be affected by mysterious forces of covert communication set into motion by subtle and poorly understood expectations. Even in such apparently simple and straightforward experiments as obtaining judgments of photographs of faces and running rats in a maze, the expectations of experimenters were somehow inadvertently leading their subjects to show the responses expected.

Later came another revelation: that such expectations not only affected behavior in the laboratory but also had powerful and significant effects in real life: The Rosenthal and Jacobson (1968) demonstration of the power of teachers' expectations in creating self-fulfilling prophecies affecting the achievement and even perhaps the apparent intelligence of their students remains one of the major contributions of the social sciences to our culture, even though our culture, and indeed the social sciences, have yet to respond adequately to its implications. The Rosenthal and Jacobson result created controversy (Jensen, 1969; Thorndike, 1968), but subsequent studies replicated their findings beyond a reasonable doubt (Harris & Rosenthal, 1985; Babad, this volume). Moreover, other studies demonstrated the power of the covert communication process in socially relevant settings: in the vocal patterns of a physician referring patients for further treatment, for example (Milmoe, Rosenthal, Blane, Chafetz, & Wolf, 1967), or in the nonverbal behavior of a judge during a criminal jury trial (Blanck, Rosenthal, & Cordell, 1985; Blanck, this volume).