By Brandy Jones, BCBA
Two events can happen before a response and still play different roles. When you are deciding between a motivating operation and a discriminative stimulus, ask what relationship the scenario describes. Timing alone will not separate them.
A motivating operation, or MO, temporarily changes the effectiveness of a consequence and changes behavior that has produced that consequence. An establishing operation increases that effectiveness; an abolishing operation decreases it. Here, we'll focus on reinforcing consequences.
A discriminative stimulus, or SD, has a different role. Through a history of differential reinforcement, it occasions a response because reinforcement has been available for that response in its presence. A useful study shorthand is value for the MO and availability for the SD. Keep the learning history and both MO effects in your explanation.
Consider a fictional café example. After a long period without drinking, water may become more effective as a reinforcer, and water-seeking responses may increase. That pattern illustrates an establishing operation. Separately, an illuminated 'open' sign can occasion entering the café if entering while the sign is on has produced access to drinks and entering while it is off has not. In that example, the sign functions as an SD for entering.
The open sign does not have to make water more valuable. Going without water does not tell you that this café is open. The two variables can work together, but they answer different questions. After adequate access to water, the same open sign may occasion less water-seeking because water is temporarily less effective as a reinforcer.
This is a conceptual example for studying, not a recommendation to restrict anyone's access to water. In practice, identify relevant variables through appropriate assessment and preserve access to basic needs.
To practice, divide a page into 'value' and 'availability.' Under value, name the consequence, how its effectiveness changes, and the related behavior change. Under availability, name the response and the differential reinforcement history. If you cannot fill in a column, note what the scenario leaves out.
One final check: calling every antecedent an SD skips the relationship that defines stimulus control. Calling any increase in responding an MO skips the value-altering effect. Make your explanation specific enough that another learner can follow it.
Review motivating operations and stimulus control with Behavior Café's existing Domain B exam-prep material. Explore the resources at behaviorcafe.com. — Brandy Jones, BCBA
