The observer-expectancy effect is a form of research bias in which an experimenter's own expectations about the outcome of a study unintentionally influence the behavior of participants, typically through subtle cues in tone, wording or body language rather than through any deliberate manipulation. It is distinct from the subject-expectancy effect, in which participants' own beliefs shape their responses, and from demand characteristics more generally. Researchers commonly guard against the observer-expectancy effect by using double-blind study designs, in which neither the experimenter nor the participant knows which condition is being tested.
Facts
Partially Attested
First Described YearWikipedia's reference list cites Rosenthal's 1966 book as the earliest source for the effect; the article text does not explicitly state this as the year the effect was first described. Core ClaimA researcher's own expectations about a study's outcome can subconsciously and subtly influence participants' behavior to conform to those expectations. 1 Classification
Type of Phenomenon Sources
1. Wikipedia: Observer-Expectancy Effect
Wikimedia FoundationOverview section
the experimenter may subtly communicate their expectations for the outcome of the study to the participants, causing them to alter their behavior to conform to those expectations.
References
Rosenthal R (1966). Experimenter Effects in Behavioral Research. NY: Appleton-Century-Crofts.
lead section, phenomenon-kind classification
The observer-expectancy effect is a form of reactivity in which a researcher's cognitive bias causes them to subconsciously influence the participants of an experiment.
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