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The observer-expectancy effect, also known as the experimenter-expectancy effect, refers to a cognitive bias where a researcher's expectations or beliefs about the outcome of a study subconsciously influence the participants of the study or the interpretation of results. This can lead to skewed outcomes that conform to the observer's preconceived notions.
This effect typically occurs when researchers inadvertently communicate their expectations to participants through subtle cues, such as body language, tone of voice, or general demeanor, thereby influencing participants' behavior. Even without direct contact, researchers may unintentionally interpret ambiguous data in a way that aligns with their expectations.
One classical example is the 'Clever Hans' phenomenon, where a horse appeared to perform arithmetic tasks. It was later discovered that the horse was responding to the subtle cues from the trainer rather than actually performing calculations. Another example is in clinical trials, where researchers may unknowingly influence patient outcomes if not properly blinded.
The observer-expectancy effect can lead to invalid results and unreliable research conclusions, contributing to biases in scientific literature. It can result in the confirmation of inaccurate theories and can waste resources on ineffective interventions or policies.
To minimize this bias, researchers can employ double-blind study designs where both participants and researchers are unaware of the critical aspects of the experiment. Standardizing procedures and using automated systems for data collection can also reduce human influence. Additionally, fostering awareness and training about this bias can help mitigate its impact.
Critics of the notion argue that awareness of personal biases and proper peer review can sufficiently counteract observer-expectancy effects. Some suggest that these biases are less impactful with the advent of technology-driven data collection and analysis.
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Rosenthal, R., & Jacobson, L. (1968)
Covert communication in laboratories, classrooms, and the truly real world
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Double-blind experiments: Protecting scientific objectivity
Rosenthal, R., and K. Fode (1963)