DISCRIMINATIVE CONTROL OF THERAPISTS' PERFORMANCE1

In order to examine therapists' discriminative responding to normal and idiosyncratic patient responses, naive subjects were presented with a simulated “patient” for treatment. The subjects were made to believe they were reinforcing normal verbalizations emitted by this patient In fact, they were listening to a tape on which normal and idiosyncratic verbalizations had been recorded. Different probabilities of normal and idiosyncratic “patient” verbalizations could be presented to the subjects by means of a digital programming unit. In one of a number of conditions, the subjects' accurate reinforcing responses were followed by an increased probability of the patient's normal verbalizations. Accurate reinforcing responses emitted by the subjects were brought under the control of normal and idiosyncratic patient responses, by use of contingent feedback, change in patient responding, and monetary reinforcers. When the patient's normal verbalizations increased in probability, so did the subjects' accurate reinforcing responses following the patient's normal verbalizations, and to a lesser degree, the subjects' inaccurate reinforcing responses following the patient's idiosyncratic verbalizations. When the patient's idiosyncratic verbalizations increased in probability, the subjects' accurate and inaccurate reinforcing responses decreased in probability. The clinical implications of these tendencies are discussed.     

Elicited responding to signals for reinforcement: the effects of overall versus local changes in reinforcement probability

Pigeons were studied on a three-component multiple schedule where all reinforcement was independent of responding. Two components were cued by different keylights and were associated with different rates of reinforcement. The third was always a no-key period associated with extinction. After a few sessions, pecking was elicited by the keylights signalling the reinforcement and continued to be maintained indefinitely. The duration and sequence of the three components were varied to determine if the primary controlling variable was differences in the overall probability of reinforcement, or if it was the immediate change in reinforcement signalled by the onset and/or offset of the stimulus. Both variables were found to control behavior. When 30-sec components were used, the primary controlling variable was the overall probability of reinforcement, but when 3-min components were used, overall probability had little effect. Control by local changes in reinforcement also occurred, although the type of local control varied both across subjects and experimental conditions. Some behaviors were controlled more by the change in reinforcement signalled by the onset of the stimulus, while others were controlled more by the change signalled by the offset of the stimulus.     

Behavioral contrast of time allocation

Pigeons' standing on a platform produced food reinforcement according to two-component multiple schedules in which either both components consisted of the same variable-interval schedule or one of these was replaced with a component without reinforcement (extinction). The components of the multiple schedule alternated every 30 sec, and were signalled by changes in the color of diffuse overhead illumination. Changing the schedule of one of the components to extinction increased the percentage of time spent on the platform during the unchanged component (behavioral contrast). This result casts doubt on accounts that attribute behavioral contrast to variations in the rate of noninstrumental elicited responses.     

INCREASING THE INDEPENDENT RESPONDING OF AUTISTIC CHILDREN WITH UNPREDICTABLE SUPERVISION

We investigated the role of predictable versus unpredictable supervision on the independent task responding of three autistic children. In a predictable supervision condition, the therapist was present in the setting for a regular period of time and then was absent for the remainder of the session. In an unpredictable supervision condition, the therapist's presence was scheduled on a random, intermittent, and unpredictable basis throughout the session. The multiple baseline analysis showed that the unpredictable supervision produced much higher levels of on-task responding during the therapist's absence for all three children. Analysis of work completed during the therapist's absence also favored the unpredictable supervision condition. The results are discussed in relation to the literature on generalization and educational practice.     

Some parameters of behavioral contrast and allocation of interim behavior in rats

Two experiments examined the effects of baseline reinforcement rate and component duration on behavioral contrast and on re-allocation of interim behavior in rats. Positive behavioral contrast occurred during multiple variable-interval 10-second extinction (VI 10 EXT) after a multiple VI 10 VI 10 baseline condition, but not during multiple VI 60 EXT following multiple VI 60 VI 60 baseline. Component duration had no significant effect on contrast. These results differed from those found in studies of pigeons' key pecking. Contrast was accompanied by an increased rate of drinking in the changed component, but drinking in the constant component did not decrease. These results are not consistent with the competition theory of contrast, but are consistent with the predictions based on the matching law. However, no current theory seems to account for all instances of behavioral contrast.     

The relationship between differential stimulus relatedness and implicit measure effect sizes

Implicit measures have been hypothesized to allow researchers to ascertain the existence and strength of relations between stimuli, often in the context of research on attitudes. However, little controlled behavioral research has focused on whether stimulus relations, and the degree of relatedness within such relations, are indexed by implicit measures. The current study examined this issue using a behavior‐analytic implicit‐style stimulus relation indexing procedure known as the Function Acquisition Speed Test (FAST). Using a matching‐to‐sample (MTS) procedure to train stimulus equivalence relations between nonsense syllables, the number of iterations of the procedure was varied across groups of participants, hence controlling stimulus relatedness in the resulting equivalence relations. Following final exposure to the MTS procedure, participants completed a FAST. Another group of participants was exposed to a FAST procedure with word pairs of known relatedness. Results showed that increasing relatedness resulted in a linear increase in FAST effect size. These results provide the first direct empirical support for a key process‐level assumption of the implicit literature, and offer a behavior‐analytic paradigm within which to understand these effects. These results also suggest that the FAST may be a viable procedure for the quantification of emergent stimulus relations in stimulus equivalence training.     

FMRI of two measures of phonological processing in visual word recognition: ecological validity matters

Previous functional magnetic resonance imaging (fMRI) studies have investigated the role of phonological processing by utilizing nonword rhyming decision tasks (e.g., Pugh et al., 1996). Although such tasks clearly engage phonological components of visual word recognition, it is clear that decision tasks are more cognitively involved than the simple overt naming tasks, which more closely map onto normal reading behavior. Our research aim for this study was to examine the advantages of overt naming tasks for fMRI studies of word recognition processes. Process models are presented to highlight the similarities and differences between two cognitive tasks that are used in the word recognition literature, pseudohomophone naming (e.g., pronounce BRANE) and rhyming decision (e.g., do LEAT and JEAT rhyme?). An fMRI study identified several differences in cortical activation associated with the differences observed in the process models. Specifically, the results show that the overt naming task involved the insular cortex and inferior frontal gyrus, whereas the rhyming decision task engaged the temporal-parietal regions. It is argued that future fMRI research examining the neuroanatomical components of basic visual word recognition utilize overt naming tasks.     

Establishing Functional Classes In A Chimpanzee (Pan troglodytes) With A Two-item Sequential-Responding Procedure

A 9-year-old female chimpanzee was trained on a two-item sequential-responding task. Attempts were made with successive-reversal training to establish functional classes. In Experiment 1, the subject was exposed to between-session successive-reversal training in which one of two pairs of stimuli was reversed, and transfer of reversal responding to the other pair was tested with nonreinforcement probe trials. She did not show transfer during the course of reversals. Stimulus control established in the original training was maintained on nonreinforcement probe trials. In Experiment 2, within-session reversals were introduced. She showed transfer from the initially reversed pair to the other. The results were consistent with Vaughan's (1988) results with pigeons on successive discriminations, which indicated the formation of functional classes. In Experiment 3, crossover and wild-card tests were conducted to clarify the stimulus control of sequential responding. The results suggested that the sequential responding was controlled only by the first stimulus of each pair. To establish control by both first and second stimuli, trial-unique stimuli or wild cards were substituted for one of the items of the lists in Experiment 4. Further transfer tests, in which stimuli for the two new pairs appeared, were also given to the subject. She successfully responded to these two merged lists and reversed the order as the result of reversal training.     

The formation of linked perceptual classes

Multiple-exemplar training with stimuli in four domains induced two new fill-based (A1' and A2') and satellite-image-based (B1' and B2') perceptual classes. Conditional discriminations were established between the endpoints of the A1' and B1' classes as well as the A2' and B2' classes. The emergence of linked perceptual classes was evaluated by the performances occasioned by nine cross-class probes that contained fill variants as samples and satellite variants as comparisons, along with nine other cross-class probes that consisted of satellite variants as samples and fill variants as comparisons. The 18 probes were first presented serially and then concurrently. Class-consistent responding indicated the emergence of linked perceptual classes. Of the linked perceptual classes, 70% emerged during the initial serial test. An additional 20% of the linked perceptual classes emerged during the subsequently presented concurrent test block. Thus, linked perceptual classes emerged on an immediate or delayed basis. Linked perceptual classes, then, share structural and fuctional similarities with equivalence classes, generalized equivalence classes, cross-modal classes, and complex maturally occurring categories, and may clarify processes such as intersensory perception.