Definition: The researcher allowing his or her expectations to affect the outcome of a study; or, in memory, a tendency to distort recalled events to make them fit one's expectations

Quite Simply...


  • Allowing your assumptions/forecasts of how you think an experiment should turn out influence or alter the results.
  • If you think something is going to happen, you're going to expect the results to be what you think.
  • You're biased because you remember things the way you would've expected them to be, which make your memories false.
  • What you expect affects the end result.

Examples of Expectancy Bias


  • When you perform an experiment and get outrageous data, you assume you must have made a mistake and don't take the data into consideration, although it may very well be valid.
  • Trying to fix something and putting the parts in the wrong place and being convinced that it was the correct and only way to make it work again.
  • Your sister "never does anything wrong", so when your mom sees the broken lamp, she automatically assumes it was you and grounds you, when it was really your sister.
  • You predicted the Saints would beat the Seahawks. Even though the game was an upset, later on, you may incorrectly recall that the Saints won because this outcome fits your expectations.
  • Taking a test and expecting to pass. You fail the test and insist the wrong answers are actually correct.
  • Being told a story of your childhood over and over again, you might think you remember it when you really don't: you just think you do because of what your parents have told you.

Side note:


  • Expectancy bias is what sometimes makes double-blind studies necessary
  • Expectancy bias often creates a fault in your long-term memory
  • Expectancy bias can change the outcome of an experiment because the results are the effect of the experimenter changing results based on what they think is supposed to happen.

Research