1) The systematic modification or maintenance of behaviour by manipulating relevant conditions. The manipulation of conditions distinguishes control from prediction and interpretations. If control is not possible because relevant conditions are not manipulable, adequate information about relevant variables may make prediction possible (e.g., as in the history of astronomy before space flight). Interpretation usually occurs after the fact. Given an outcome, a plausible account of the relevant variables can be offered, but it may be difficult to determine its adequacy. Nevertheless, such an analysis is often expected or demanded of students of behaviour (as when a psychologist is asked to explain in a court of law why a defendant acted in some way). In its most common behaviour analytic usage, the term appears in conjunction with some variable that has a demonstrable effect on behaviour (e.g., schedule control, stimulus control).

2) The term control expresses the functional relation between a performance and the variable of which it is a function. Thus we say, "A performance is under the control of a level of deprivation," as a synonym for, "The performance is a function of the level of deprivation," or, "The performance changes when there is a change in the level of deprivation."