Expectancy bias (also known as observer-expectancy effect) refers to the subconscious influence that a researcher can have on the subjects of a research study. It is a type of cognitive bias that can affect researchers. The reactivity from expectancy bias is not planned but can affect the results of a study through a confirmation bias. A confirmation bias can cause a researcher to interpret results in accordance to their desired end and ignoring data that does not conform to the desired results. This can be a threat to the internal validity of the studies involved.