This question requires a clear understanding of the distinction between a Motivating Operation MO and a Discriminative Stimulus SD A Motivating Operation MO is an environmental variable that has two primary effects a it alters increases or decreases the reinforcing or punishing effectiveness of some stimulus object or event and b it alters increases or decreases the current frequency of all behavior that has been reinforced or punished by that stimulus object or event In this specific scenario the commercial functions as an establishing operation EO It increases the reinforcing effectiveness of the bean burrito making you want it more and evokes behavior driving to Taco Bell that has historically been reinforced by obtaining that burrito The commercial motivates you to seek out the burrito Conversely a Discriminative Stimulus SD is a stimulus in the presence of which a particular response has been reinforced in the past It signals the availability of reinforcement for a specific behavior The Taco Bell sign seen upon your arrival at the restaurant functions as an SD signaling that the restaurant is open and the burrito is now physically available for purchase The key difference is that the commercial precedes the physical availability of the burrito at your location it generates the motivation or desire for the burrito rather than signaling its immediate availability in that exact moment MOs change what you want and how much you want it while SDs signal when and where what you want is available to be obtained