I think it can be fairly said that one of the most significant impediments to the general acceptance of behavior analysis as a complete account of human functioning is the problem of word meaning. The notion of word meaning is still one of the most cognitive of notions, but some account is mandatory if the behavioral approach is ever to provide a comprehensive description of thought and language. To see some possible solutions to this problem, we may begin by appreciating the fact that current usages of the term meaning refers to two different kinds of behavior. One kind is the expressive behavior of the speaker who expresses meanings, and the other is the receptive behavior of the listener who gets, or comprehends meaning. Skinner’s account of the expressive behavior of the speaker is fairly complete, and so it is the latter topic, the receptive behavior of the listener, that most needs to be considered.
Let us begin this examination by considering a simple form of receptive behavior: selecting stimuli in response to other stimuli. as in a conditional discrimination. In this task an array of comparison objects are presented, here a triangle and a square, and the subject must select one object in response to the sample object – here a square. On the usual account of this behavior, henceforth referred to as unmediated selection., it is said that due to a history of reinforcement, the sample serves as a conditional stimulus, making one of the comparisons function as a SD for a selection response. Thus, here, the sample square functions to make the comparison square act as an SD. This produces an increase in the momentary rate of the pointing response, thereby causing the square comparison to be selected.
Where one of the stimuli is a word, the same account applies unchanged. Thus, as we see in this next picture (Figure 2), we may explain the selection of a square, in response to the spoken word “square” and likewise the selection of the printed word “square” in response to the object, in exactly the same terms: The sample, as a conditional stimulus, makes one of the comparison into an SD for the pointing response.
As a demonstration of joint control consider the task shown in Figure 5 in which you must locate a particular 6-digit number in an array in response to the spoken sample 939173. Take a moment to find 939173 in this array. Now finding the correct number required joint control. This next slide illustrates what this is.
Look at the top of Panel A. in
Figure 6. First off, after you read the spoken sample 939173, you
began to peruse the array looking for that number. As you did so,
you repeated the sample number. In the language of Skinner’s verbal
operants, this would be described as echoic rehearsal of the sample,
and it is illustrated along the top of Panel A.
Second, as illustrated in the bottom of Panel A, as you perused the array, you also attempted to tact each 6-digit number, and you continued doing this until, as illustrated here, you encountered a particular 6-digit number that you could emit both as a tact, and simultaneously as the rehearsed self-echoic.
That is, at some point you could say 939173 both as a tact of the printed number, and jointly as a self echoic rehearsal of the spoken number. And so, at this point you were repeating the number 93173 under joint tact/echoic control. This event, this onset of joint control, is a unique source of stimulus control because it only happens when the specified comparison is encountered. Indeed, the onset of this joint self-echoic/tact control is in fact the only possible way you can identify which number in the array was the one I said.
Now it is also important to note here that even though this is a matching to sample task, you were all able to recognize the specified number without actually emitting a pointing response to the number itself. Rather, you simply relied upon the onset of joint control to determine when you had located the correct number. It would thus appear that the onset of joint control is the event one would identify as the event of recognizing the specified number set. You could then report this recognition event, by emitting the autoclitic “I found the number”.
But, as illustrated in the lower part of the figure, in Panel B, had there been a request that you point to the specified number set, you could have easily conformed to my mand, and pointed to it.. As discussed elsewhere, such a pointing response may be described as a selection-based autoclitic response, a response reporting to others which number in the array entered into joint stimulus control with the self-echoic you were already rehearsing. Let’s look at this more closely.
In Figure 7) the sample is: Black dot
in a smaller pentagon. Now again, as you peruse the comparisons you
rehearse the sample phrase as a self-echoic. And when a comparison
is found that evokes this same topography, both as a tact of that comparison,
and jointly as an echoic rehearsal of the sample, you report the source
of this joint control by an autoclitic pointing response.
Together, this example and the prior number-finding task, illustrate that the joint-control event is generic, and thus independent of any particular stimuli. Thus, in these two tasks it didn’t matter whether it was the names of numbers or the names of colors, shapes, or relative sizes. In all cases, whenever the self-echoic comes under joint control, this event, this onset of joint control, is itself a common generic event. And it is this generic event that evokes a report of recognition and/or a pointing response. As we shall see next, the generic nature of joint control makes it surprisingly ubiquitous in our verbal behavior: producing a variety of behavioral phenomena typically attributed to the semantic notion of word meaning.
We shall begin this examination with
a consideration of how words are tied to the objects they specify. That
is, exactly how do words specify objects and events?
Lets look at the experiment shown in Figure 8. In this experiment, prior to learning a matching to sample task, we trained retarded children to make the handsigns shown in Panel A to each of the corresponding shapes when these were shown alone. In the next phase of the experiment, -- shown in Panel B-- the children were trained to make the correct handsign to the sample, and then to rehearse the handsign over a delay interval, and then to continue to rehearse the handsign as they matched it to the correct comparison. Subjects thus learned to use the handsigns to mediate identity matching to sample behavior. Subsequently, when identity matching was tested with the novel stimuli shown in Panel C, there was no generalized matching. But after only training handsigns to these novel stimuli, subjects immediately showed unreinforced generalized identity matching with these new stimuli, thus illustrating that this form of stimulus control, joint control over matching, somehow incorporates relations between the stimuli, so that one subsequently novel stimulus may indeed specify the selection of an identical other. That is, generalized identity matching to sample.
The way this works is not hard to see.
Thus, as we see in Figure 9 the handsign to the two-dot sample is a tact,
and maintaining the handsign over the delay interval is a self-duplic.
And selection of the comparison occurs when the two sources of control
operate jointly. Thus we see that the handsign is jointly evoked
both as a self-duplic rehearsal, and simultaneously as a tact, only with
one particular comparison. Thus the two dots, as a sample,
evoke the handsign illustrated, and if this handsign is maintained over
the interval (as a duplic), it is jointly evoked by the two-dot comparison.
Likewise, in the lower part of the figure, in Panel B the line, as a sample,
evokes the handsign illustrated, and if this handsign is maintained over
the interval, it is jointly evoked by the line comparison.
The way one stimulus specifies another is thus revealed. The sample stimulus specifies a comparison stimulus because the sample stimulus evokes a particular handsign, and this handsign can only enter into joint control with one particular comparison. Thus the two-dot sample evokes the particular handsign shown here, and that handsign can occur under joint control only with the-two dot comparison. Likewise in the bottom figure, the sample line specifies the line comparison because the sample line evokes the illustrated handsign, and that handsign only enters into joint control with the line comparison.
It can only be briefly noted here that
this account goes beyond the comprehension of nouns, but extends to the
description of abstract relations as well Thus, we are able to identify
box on circle and circle under box with one stimulus, and box under
circle and circle on box with another only because of the manner in which
each description enters into joint control with tacts of the various stimuli
and certainly not because of any simple correspondence between the words
of the descriptions and the elements of the object described.
Let us conclude with an observation, Viewed through the notion of joint control, we see that specification, description, recognition and comprehension seem to be different aspects of a single process of stimulus control. Joint control thus provides a simple behavioral mechanism to account for many allegedly cognitive and semantic functions. And in doing so it increases the utility, and thus the plausibility, of Skinner’s account of verbal behavior. Though research on this topic is not easy, I think the conceptual path is quite clear and should be explored.