Establishing operations (EOs) have emerged in behavior analysis over the past decade as a way of understanding motivation. EOs were originally incorporated into behavior analysis in the 1950s, but for reasons that are unclear, they were not included in subsequent conceptualizations of operant behavior. Instead, behavior has been conceptualized as having three key elements: Discriminative stimuli (SD), responses (R), and reinforcing stimuli (SR). These elements are also referred to more generally as antecedents, behaviors, and consequences. In this three-term contingency, an SD is an event that signals the availability of a reinforcing stimulus if a response is emitted (i.e., SD→R→SR). For example, when a friend enters the playground (SD), a student greets the child (R), and the friends begin interacting (SR). This three-term unit ...