confederate
n. countablen. a person who helps someone else do something, often in secret or for a specific plan. In science experiments, this is a person who pretends to be a participant but is actually working for the researcher.
n. an accomplice or associate in a plot or secret undertaking; in psychological research, an actor who participates in an experiment while pretending to be a subject.
The researcher asked a confederate to sit in the waiting room.
In the famous study on conformity, a confederate gave the wrong answer to see if the real subject would follow.
The success of the social experiment relied entirely on the confederate maintaining a convincing facade of ignorance while subtly influencing the group's decision-making process.
In a psychological context, it refers specifically to an individual working for the experimenter. When capitalized, it refers to the American Civil War era.