Motivating operations (MOs) are held to 1) alter the value/efficacy of consequential stimuli (value-altering function) and 2) alter behavior relevant to these stimuli (behavior-altering function). These two functions are considered critically against empirical evidence to evaluate the extent to which each corresponds to actual observations of behavior-environment relations. On this basis, the following refinements are suggested. First, positing a value-altering function of MOs is unnecessary because observations that have been taken as evidence for this function are adequately and parsimoniously described in terms of MOs’ behavior-altering functions, particularly their effects on the evocative efficacy of discriminative stimuli that have been associated with certain consequential events. Second, the precision of descriptions of the behavior-altering functions of MOs may be increased by explicitly acknowledging that MOs serve multiple functions. In addition to their motivational functions, MOs affect behavior by serving eliciting, discriminative, and reinforcing or punishing functions. Interactions between the effects of different MOs and biologically-based individual differences in susceptibilities to certain MOs also play a role determining their behavior-altering functions. In surveying the existing empirical literature relevant to these issues, areas in which further investigation is needed are highlighted.
Motivating Operations and Discriminative Stimuli: Distinguishable but Interactive Variables