What are the functions of the stimuli in a behavioral chain?

Revised on 3/29/14

The dual-functioning stimuli that link the responses in a behavioral chain function as reinforcers for the behaviors that precede them. The 1st stimulus or condition that starts the chain doesn't link two behaviors, so in analyzing a chain, we normally don't label that one as a reinforcer. The 2nd function of these stimuli may be S^D, EO, operandum, or opportunity to respond. This last option is not discussed in Ch. 20. It's briefly discussed in Ch. 22 (p. 354) but it's relevant here too. Without having it as an option for the 2nd function of these linking stimuli, we're handicapped in some cases. Anyway, figuring out which of these functions applies to a particular dual-functioning stimulus is one of the trickier things to do when analyzing a behavioral chain.

In this chapter, Malott's only discussion of a stimulus functioning as an EO is in the footnote at the bottom of p. 315, where he assigns that function to the stimulus that starts the behavioral chain he's describing. Can a dual-functioning stimulus in the middle of a chain also have the EO function? I think it can because the introduction of an EO increases the likelihood that the next behavior in the chain will occur, and that's the sort of thing these linking stimuli do to keep the behaviors happening one after the other. But that's not my main concern in this post.

My main concern is this opportunity to respond option. In Ch. 22 we're going to learn about analogs to discriminated avoidance. These are situations in which there's a deadline and the target behavior has to happen before the deadline or else you lose the chance to receive a reinforcer. We'll learn that in lots of these scenarios, the time before the deadline functions as an S^D, meaning that if the target behavior happens before the deadline, it's reinforced. And in those scenarios, the time after the deadline functions as an S^Δ, meaning that if the behavior happens after the deadline, it won't be reinforced. But, Malott explains to us, the time before a deadline doesn't always function as an S^D. It's not an S^D in cases where the target behavior, for various possible reasons, cannot be performed after the deadline has expired. If the target behavior can't be performed, this means the time after the deadline is not an S^Δ, which means that the time before the deadline is not an S^D. So if the time before the deadline is not an S^D, what is it? According to Malott, that stimulus condition is best labeled as an opportunity to respond (again, see p. 354).

Are you still with me? OK, then here we go, back to those dual-functioning stimuli in behavioral chains. When my students think up examples of behavioral chains, they sometimes have trouble figuring out the function of the stimulus/condition described in the 1st box as well as the other linking stimuli. I now realize that there are 4 possibilities: S^D, EO, operandum, or opportunity to respond. As an example of opportunity to respond, consider the example provided by one of my students. The 1st box says "Car is parked." The following behavior box says "Start car." The following dual-functioning stimulus box says "Car running." Is that first stimulus condition (Car is parked) an operandum? I don't think so. Is it an EO? I don't think so because if it was, that would mean that when the car is parked, the reinforcement value of "car is running" would be greater than if the car was not parked, that is, if the car was running or being driven. This doesn't make sense because in the latter condition (car is running or being driven), the behavior of starting the car can't be performed because the car is already started. Is it an S^D? I don't think so because the corresponding S^Δ would then be "car is running/being driven." And again, in that condition the behavior of starting the car couldn't be performed because the car is already running. So what's the function of the condition described in that first box, "car is parked?" I think it's an opportunity to respond.

So some quick guidelines for figuring out the functions of the initial stimulus/condition and the linking stimuli:

Is it an S^D? Figure out what its corresponding S^Δ would be. Then ask yourself two questions: (1) In the S^Δ condition, could the following behavior be performed? If not, then this condition is not an S^Δ, which means that the stimulus/condition in question is not an S^D. (2) In the S^Δ condition, if the following behavior could be performed, would it be followed by the reinforcer that's described in the next stimulus box? If so, then then this condition is not an S^Δ, which means that the stimulus/condition in question is not an S^D.

Is it an EO? Look at the reinforcing stimulus that results from the behavior. Is it a more powerful reinforcer for the behavior because of the presence of the stimulus/condition in question? If so, then it's an EO.

Is it an operandum? Does the stimulus/condition constitute making available some "thing" that you must have in order to perform the following behavior? An example is "fork in hand" when the following behavior (such as "put fork in potato") can't be performed without that "thing." If so, then it's an operandum.

Is it an opportunity to respond? Similar to operandum in that without either - operandum or opportunity to respond - the following behavior can't be performed. Here, tho, the inability to perform the behavior is not because some implement or object is not available, but for some other reason it's not possible to perform the behavior, like in the "car is parked" example above.

Have fun figuring out the dual functions of these linking stimuli in behavioral chains!