In research, and particularly psychology, demand characteristics refers to an experimental artifact whereby participants unconsciously change their responses after forming an interpretation of the experiment's purpose. Demand characteristics are typically to be confounding variables, affecting participant behaviour in ways other than intended by the researcher.
- Orne, Martin T. Demand Characteristics and the concept of Quasi-Controls. in Artifacts in Behavioral Research: Robert Rosenthal and Ralph L. Rosnow's Classic Books, beginning with page 110
See also 
- Demand characteristics (Wikipedia)