Observer-expectancy effect

The observer-expectancy effect occurs when an observer’s expectations influence how they perceive, record, or interpret behavior or experimental results.

Confirmation bias: The tendency to seek, notice, and interpret information in ways that support existing beliefs. Expectations can direct attention toward evidence that confirms them.
Robert Rosenthal: An American psychologist known for research on experimenter expectations and self-fulfilling prophecies. His studies helped establish observer expectations as an experimental bias.
Double-blind study: A study design in which both participants and relevant researchers are unaware of treatment assignments. It limits both participant and experimenter expectations from influencing outcomes.
Experimenter effect: The influence of a researcher’s presence or behavior on participants or experimental results. It includes pathways through which researchers’ expectations can change study outcomes.
Demand characteristics: Cues in a study that reveal its purpose and can influence participants’ behavior. Participants may respond to perceived expectations, while this effect centers on observers.
Rosenthal effect: The influence of an experimenter’s expectations on participants’ outcomes or behavior. This closely related name emphasizes effects on participants, not just observation.
Observer bias: Systematic distortion in data collection or interpretation caused by an observer’s characteristics or expectations. This broader label covers distortions that can arise even without explicit predictions.
Self-fulfilling prophecy: A prediction that helps bring about the outcome it predicts through actions shaped by that belief. Observer expectations can become consequential when they alter treatment or interaction.
Blinding: The practice of concealing study assignments or information from participants, researchers, or assessors. Masking group identities can prevent expectations from shaping observations.
Clever Hans: A horse whose apparently mathematical responses were guided by subtle cues from people watching him. The case showed how observers could unintentionally cue the behavior they assessed.

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