1. self-fulfilling prophecy: a situation in which a researcher’s expectations influence that person’s own behavior, and thereby influence the participant’s behavior

2. single-blind experiment: an experiment in which the participants are unaware of which participants received the treatment

3. double-blind experiment: an experiment in which neither the experimenter nor the participants know which participants received which treatment

4. placebo effect: a change in a participant’s illness or behavior that results from a belief that the treatment will have an effect rather than from the actual treatment