Expectancy Effects

Expectancy Effects are the results that an experimental researcher or observer generates when they have somehow, usually subtly and subconsciously, communicated the expected results to the participant. In other words, the experimenter gives away the purpose, direction, meaning, etc., of the experiment to the participants - not good!

This happens frequently when a subject (human or animal) learns to associate an unintended stimulus (a sound, gesture, facial expression, etc.) with an expected action or response.