Behaviorism

About Dick
Malott.com

Q&A: Chapter 15 Avoidance

Q. What is the difference between a Warning Stimulus and a Discriminative Stimulus? (EPB 4.0 page 255)
A. A buzzer goes on, and 3 seconds later a shock comes on for a few seconds. If the rat presses the lever within the 3 seconds after the buzzer comes on, the buzzer will go off, and the rat will have avoided the shock (the shock won't come on). The buzzer is the warning stimulus that occurs before the presentation of the shock.What is the difference between a Warning Stimulus and a Discriminative Stimulus? Traditionally, behavior analysts have analyzed this contingency as if the warning stimulus were a discriminative stimulus. However, we think it's better to look at the warning stimulus as the before condition.

Correct One

Traditional One

Q. Why is the warning stimulus the before condition rather than the S^D.
A. Remember that, if we have an S^D, we must have an S^Δ. So, let's diagram the contingency as if the buzzer on were the S^D. And, then, of course, the buzzer off will be the S^Δ. (It's the wise student who diagrams his or her way out of confusion. This diagram may look good at first glance, but there are problems. Focus on the S^Δ contingency.

1. The before condition is shock will come on in 3 seconds; but in our example, the shock won't come on if the buzzer is off, right? Remember the buzzer is the warning stimulus that precedes the shock. So if there's no buzzer, there will be no shock in 3 seconds. So we can't specify shock will come on in 3 seconds as the before condition in the preceding diagram. So, we don't really have an S^Δ; and if we don't have an S^Δ, we don't have an S^D, according to our criteria for diagramming discriminated contingencies.
2. We should change the before condition for the S^Δ to shock will not come on in 3 seconds. But we can't. Why not? According to our criteria for diagramming discriminated contingencies, the before condition must be the same for both the S^D and the S^Δ contingencies; and that's not possible, if we have the shock will not come on for the before condition for the S^Δ and the shock will come on for the S^D.