n.1. behavior designed to exploit, control, or otherwise influence others to one’s advantage. 2. in an experimental design, the researcher’s adjustment of an independent variable such that one or more groups of participants are exposed to specific treatments while one or more other groups experience a control condition. For example, a health researcher could introduce a manipulation so that a portion of the participants in a study randomly receive a new drug, whereas the remaining participants receive only a placebo. See experimental variable.