Informal Definition

Demand characteristics refer to behavior that can sometimes be exhibited during psychological experiments. This occurs when a person who is involved in an experiment has been influenced in someway. The psychologist or person giving the test can give subtle hints or clues as to the outcome of the test and what is to be expected. Instead of giving an honest answer, the person being tested may change some or all parts of the answer to conform to what the tester is looking for. Demand characteristics can change behaviors to seem more socially or morally responsible.

wikipedia

In research—particularly psychology—demand characteristics refers to an experimental artifact where participants form an interpretation of the experiment’s purpose and unconsciously change their behavior to fit that interpretation. Pioneering research was conducted on demand characteristics by Martin Orne. Typically, they are considered an extraneous variable, exerting an effect on behavior other than that intended by the experimenter.

A possible reason for demand characteristics is the participant’s expectation that he or she will somehow be evaluated and thus figures out a way to ‘beat’ the experiment to attain good scores in the alleged evaluation. Demand characteristics cannot be eliminated from experiments, but demand characteristics can be studied to see their effect on the experiment. Examples of some common demand characteristics: