The observer-expectancy effect is a cognitive bias where a researcher's expectations can subconsciously influence the outcomes of their experiment. This reactivity often leads to confirmation bias, causing researchers to misinterpret their findings in favor of their hypotheses while ignoring contrary evidence. It poses a significant threat to the integrity and validity of experimental data, necessitating procedures like double-blind designs to mitigate its impact.
A classic example of the observer-expectancy effect is the case of Clever Hans, a horse that seemingly demonstrated arithmetic abilities. Research later revealed that the horse was responding to subtle cues and body language from its handler, rather than actually performing math tasks.
To mitigate the observer-expectancy effect, researchers can implement double-blind experimental designs, ensuring that both the participants and the experimenters are unaware of critical aspects of the study, which helps reduce bias and maintains objectivity.