Discriminative functions based on a delay in the reinforcement relation

Pigeons were shown to come under discrimination control when the S^D and S^Δ were temporally separated from reinforcement and non-reinforcement. S^D and S^Δ consisted of distinctive key illuminations presented separately. Responding on an FR 5 in the presence of S^D or S^Δ produced a third stimulus containing a schedule requirement. If this third (or interpolated) stimulus was preceded by S^D, responding in its presence produced reinforcement followed by a time-out (TO). If, on the other hand, the third stimulus was preceded by S^Δ, responding produced TO alone. In this fashion, the same stimulus and the same response requirement were imposed between S^D and the reinforcement as between S^Δ and the TO. In Experiment I, the schedule employed during the interpolated stimulus was FR; in Experiment II, FI. Discrimination reversal was accomplished in both experiments.     

Human Intelligence After Removal of Cerebral Tissue from the Right Frontal LOBE

Present research explored the effect of conditioning history on the performance of imitative behaviors when a choice was given between a reinforced and a nonreinforced behavior or between two reinforced behaviors. The conditioning history consisted of exposure to a repeatedly demonstrated reinforced behavior (S^Dc). During subsequent choice presentations the S^Dc behavior was paired with a reinforced (S^Da) or nonreinforced (S-delta) alternative behavior. A multiple baseline design was utilized to control for the effect of the length of conditioning history. Six institutionalized retarded children served as subjects. The results indicated that the two subjects with no conditioning history imitated the S-delta behaviors as often as the S^Da behaviors and consistently more often than the S^Dc behaviors. In contrast, three of the four subjects who had the conditioning history imitated the S^Dc behaviors more often than both other behaviors and eventually stopped imitating the S-delta behavior. The fourth subject with a conditioning history did not show this response pattern, but showed a preference for imitating the last of two modeled behaviors. No systematic differences in imitative performance were observed between the two pairs of subjects with a conditioning history as a function of the length of conditioning history. The results suggest that the conditioning history may be largely responsible for the differential imitative performance of reinforced and nonreinforced behaviors.     

Generalization gradients following two-response discrimination training

Stimulus generalization was investigated using institutionalized human retardates as subjects. A baseline was established in which two values along the stimulus dimension of auditory frequency differentially controlled responding on two bars. The insertion of the test probes disrupted the control established to the two S^Ds during training. The discrimination was recovered between each test probe and the resulting gradients were stable across 10 test sessions. These gradients, supported by other two-response generalization studies, indicate that this type of two-response discrimination training divides the stimulus dimension into two functional classes separated by a region of transition from one class to the other. Each stimulus value in a class, which extends from an S^D outward to the functional limit of the dimension, controls a similar proportion of the two responses as each other value in the class. All values on the stimulus dimension control identical response rates with an absence of the usual generalization decrement. The latency of the initial response, however, shows a bimodal gradient with the modes at the S^D values.     

Operant control of vocal behavior in the cat

Evidence of operant control of vocal behavior in the cat is presented: (1) On mult FR 12 S^Δ schedule, cats miaowed rapidly during periods of S^D and much less or not at all during S^Δ. (2) This control was re-established following reversal of stimuli. (3) The frequency distribution of response durations was shifted to both shorter and longer values by the differential reinforcement of shorter or longer response durations respectively. Since both the frequency and duration of vocal responses were shown to be under the control of the schedule of reinforcement, it is concluded that at least some of the vocal behavior of the cat is susceptible to operant control.     

Associations in human instrumental conditioning

Four experiments were conducted to study the contents of human instrumental conditioning. Experiment 1 found positive transfer between a discriminative stimulus (S^D) and an instrumental response (R) that shared the outcome (O) with the response that was originally trained with the S^D, showing the formation of an S^D → O association. Experiment 2 found that post-acquisition devaluation of an outcome selectively reduced the response trained with that outcome, showing the formation of a R → O association. In Experiment 3, changing the outcome did not prevent participants from giving the response learned with each S^D, even though none of the responses was appropriate for the new outcome, showing evidence of the formation of S^D → R associations in instrumental learning. The three binary associations were shown within the same basic experimental situation. Finally, Experiment 4 found evidence of the formation of the higher order association S^D(R → O) in human instrumental conditioning.     

Generalization and discrimination as a function of the SD — SΔ intensity difference

Three groups of four rats were trained on an auditory-intensity discrimination for 21 days. The S^D-S^Δ intensity difference for Group I was 10 db; for Group II, 20 db; and for Group III, 30 db. Following the initial discrimination training, the animals were tested for generalization of the bar-press response to seven novel S^Δ's which were presented intermingled with the original S^D and S^Δ values. Conclusions: (1.) The amount of simple discrimination training required to obtain fairly stable differences in S^D and S^Δ responding is an inverse function of the magnitude of the stimulus difference between S^D and S^Δ. (2.) Generalization gradients obtained immediately following simple discrimination training exhibit a maximum displaced from S^D in a direction also away from S^Δ. (3.) Gradients obtained following continued exposure to the multivalued S^Δ situation show a fairly stable maximum at the S^D value. (4.) Although the gradients tend to fall off systematically on either side of the continuum as distance from S^D is increased, they decrease most rapidly on the S^Δ limb of the gradient.     

Using neutralizing routines to reduce problem behaviors.

Establishing operations can alter problem behaviors by changing the momentary value of reinforcers associated with those problem behaviors. If establishing operations (EOs) precede the presentation of discriminative stimuli (S^Ds) for problem behaviors, it may be possible to introduce neutralizing routines that both reduce the value of reinforcers associated with problem behaviors and decrease the occurrence of problem behaviors. The present study examined this logic with 3 adolescents with severe intellectual disabilities. Initial functional analyses indicated that problem behaviors were motivated by either escape or tangible items. Functional assessment interviews identified possible establishing operations that were associated with the occurrence of problem behavior and indicated that these establishing operations occurred over 1 hr before presentation of the S^D for problem behaviors. We used an alternating treatments design to examine problem behaviors during instruction under four conditions: EO + S^D, S^D only, EO only, and neither S^D nor EO. For all 3 participants, problem behaviors occurred almost exclusively during the EO + S^D condition. A further analysis compared the EO + S^D condition when neutralizing routines were embedded between the EO and the S^D. Results from an ABAB reversal design supported the effectiveness of neutralizing routines to reduce these problem behaviors. Applied and theoretical implications are discussed.     

Mitigating resurgence of destructive behavior using the discriminative stimuli of a multiple schedule

Results of several recent translational studies have suggested that correlating contextual or discriminative stimuli with the delivery and withholding of reinforcement for the functional communication response (FCR) may mitigate resurgence of destructive behavior, but few, if any, have isolated the effects of those stimuli. In the present study, we first trained the FCR, brought it under stimulus control of a multiple schedule, and thinned its reinforcement schedule in one stimulus context. Next, we conducted resurgence evaluations (i.e., baseline, functional communication training [FCT], extinction challenge) in two novel contexts to test the effects of the discriminative stimuli on resurgence. We programmed one context to include the (a) S^D during the FCT phase to signal the availability of reinforcement for the FCR and (b) S^Δ during a subsequent extinction challenge to signal the unavailability of reinforcement for the FCR. The other context did not include the S^D during the FCT phase, nor the S^Δ during the extinction challenge. We expected to see greater persistence of the FCR in the context that included the S^D during FCT and less persistence of the FCR and less resurgence of destructive behavior in the context that included the S^Δ during the extinction challenge. Obtained results confirmed this latter prediction, but we observed no reliable difference when the S^D was present or absent during the FCT phase. Our results have relevance for practitioners in that they provide further empirical support for the use of discriminative stimuli when treating destructive behavior.     

ESTABLISHING DISCRIMINATIVE CONTROL OF RESPONDING USING FUNCTIONAL AND ALTERNATIVE REINFORCERS DURING FUNCTIONAL COMMUNICATION TRAINING

Functional communication training (FCT) is a popular treatment for problem behaviors, but its effectiveness may be compromised when the client emits the target communication response and reinforcement is either delayed or denied. In the current investigation, we trained 2 individuals to emit different communication responses to request (a) the reinforcer for destructive behavior in a given situation (e.g., contingent attention in the attention condition of a functional analysis) and (b) an alternative reinforcer (e.g., toys in the attention condition of a functional analysis). Next, we taught the participants to request each reinforcer in the presence of a different discriminative stimulus (S^D). Then, we evaluated the effects of differential reinforcement of communication (DRC) using the functional and alternative reinforcers and correlated S^Ds, with and without extinction of destructive behavior. During all applications, DRC (in combination with S^Ds that signaled available reinforcers) rapidly reduced destructive behavior to low levels regardless of whether the functional reinforcer or an alternative reinforcer was available or whether reinforcement for destructive behavior was discontinued (i.e., extinction).     

On the discriminative control of concurrent responses: the relations among response frequency, latency, and topography in auditory generalization

Human subjects were used in a study of auditory generalization following multiple-response discrimination training. The relations observed among stimulus intensity, response probability, and response latency were invariant with respect to whether the two vocal responses conditioned were topographically discrete, as in one experiment, or topographically continuous, as in another. The major findings were:

1. The probabilities associated with a specific response were maximal over several stimulus values at the extreme ends of the continuum, then dropped sharply at stimuli intermediate to the initial S^D's as the probability of the alternative response increased.

2. Overall response latency was inversely related to the relative frequency of the two responses at each stimulus value. When the two responses were most nearly equal in probability, latencies were maximal; when one response had close to unit or zero probability, latencies were minimal.

3. Analysis of the latencies of the two responses, taken separately, revealed: (a) an increase in latency as the difference between the test stimulus and the initial S^D increased; (b) a sharp discontinuity in the latency gradient and reversal in trend at intermediate stimulus intensities; and (c) at a given stimulus value, latencies associated with the stochastically dominant response were consistently shorter than those of the nondominant response.

4. No changes in response topography (fundamental frequency) were correlated with the characteristic changes in probability and latency during stimulus generalization.

     

WITHIN‐SUBJECT REVERSIBILITY OF DISCRIMINATIVE FUNCTION IN THE COMPOSITE‐STIMULUS CONTROL OF BEHAVIOR

According to the composite-stimulus control model (Weiss, 1969, 1972b), an individual discriminative stimulus (S^D) is composed of that S^D''s on-state plus the off-states of all other relevant S^Ds. The present experiment investigated the reversibility of composite-stimulus control. Separate groups of rats were trained to lever-press for food whenever a tone or a light S^D was present. For one group, the nonreinforced S^Δ condition was tone-and-light absence ($\bar{T}$+$\bar{L}$). Tone-plus-light (T+L) was S^Δ in the other group. On a “stimulus compounding” test that recombined composite elements, maximum responding occurred to that composite consisting only of elements occasioning response increase. That was T+L for the group trained with $\bar{T}$+$\bar{L}$ as S^Δ and $\bar{T}$+$\bar{L}$ for the group trained with T+L as S^Δ. The S^Δ composite was next reversed over groups in Phase 2. In Phase 2 tests, maximum responding that was comparable in magnitude to that of Phase 1 was again controlled by the composite consisting only of elements most recently occasioning response increase—whether T+L or $\bar{T}$+$\bar{L}$. The inhibitory conditioning history of both composite-elements currently occasioning responding did not weaken the summative effect. These results confirm and extend Weiss''s composite-stimulus control model, and demonstrate that such control is fully reversible. We discuss how translating conditions of the stimulus-compounding paradigm to a composite continuum creates a functional and logical connection to intradimensional control measured through stimulus generalization, reducing the number of different behavioral phenomena requiring unique explanations.     

The effect of multiple S periods on responding on a fixed-interval schedule: IV. Effect of continuous S with only short S probes

Pigeons were studied under FI 500 sec in which an S^Δ was present throughout the interval except during the terminal 50-sec segment and one earlier 50-sec segment. Very little responding occurred during the presence of S^Δ. The rate of responding in the earlier 50-sec S^D segments was lower than in the terminal S^D segment. There was a clear trend for the rate of responding in the earlier S^D segment to be progressively higher the later it occurred in the course of the FI 500 sec. This trend was shown roughly to parallel the increasing rate of responding in a conventional FI 500 sec with no interruption by S^Δ. Since the changing tendency to respond through the FI survives massive disruption by S^Δ, it is concluded that the control of responding through the FI does not require continuous mediating behavior. It is suggested that it is the decaying retroactive influence of the reinforcer on responses that occurred longer and longer before the reinforcer occurred which produces the familiar scalloped pattern of responding under FI schedules.     

Some notes on time out from reinforcement

Pigeons produced food on a fixed-ratio schedule by pecking at one key, and an S^Δ period by pecking at a second (switching) key. Switching behavior was examined as a function of (a) size of the fixed ratio, (b) whether the S^Δ was of fixed duration or could be determined by the bird, (c) the introduction of a novel food S^D, (d) extinction of food responding, and (e) the stimuli associated with the S^D and S^Δ conditions. No monotonic relationship was obtained between ratio size and switching behavior. Switching behavior was, however, influenced by many variables. The results suggest that an interpretation of switching behavior in terms of its being reinforced by the removal of aversive conditions, is open to considerable question.     

Fear as a discriminative stimulus for an appetitive instrumental response

Two experiments tested the hypothesis that anticipation of shock could be established as a discriminative stimulus for an appetitive instrumental response. In multiphase experiments, bar pressing for food was brought under the discriminative control of intermittent and gradually increasing electric shock. In a second phase, tones were estalished as either a CS+, or CS? for shock. Subsequently, the CSs were introduced on to the operant baseline. Animals trained with shock as the S^D showed an increase in responding to the CS+ and a slight decrease to the CS?. Conversely, animals trained with shock as the S^Δ showed decreased responding to the CS+ and slight increase to the CS?. These findings are seen as supportive of the Discriminative Stimulus hypothesis of learned resistance to punishment.     

Transfer of conditioned fear and avoidance: Concurrent measurement of arousal and operant responding

A reversal design was employed for the analysis of transfer of fear and avoidance through equivalence classes. Two 5-member equivalence classes (A1-B1-C1-D1-E1 and A2-B2-C2-D2-E2) were established. Then B1 and C1 were paired with shock (CS+) and served as S^Ds in avoidance training (B2 and C2 were trained as CS-/S^∆s for avoidance). Further avoidance training followed with D1 and E1 (as S^Ds) and D2 and E2 (as S^∆s), with the first presentation of each of these stimuli serving as the first transfer test. Afterwards, aversive conditioning contingencies were reversed: B2 and D2 were paired with shock and trained as S^Ds for avoidance, B1 and D1 were presented without shock (CS-/S^∆s). Transfer was tested again with C1, E1, C2 and E2. This reversal was implemented to allow for the within-subject replication of transfer effects upon changes in the function of only a subset of each class's elements. Avoidance (key presses) and conditioned fear (skin conductance and heart rate) were simultaneously measured. Results show a clear transfer effect for avoidance, with between- and within-subject replications. For physiological measures, transfer effects in the first test could only be imputed on the basis of group-based inferential statistical analysis. Evidence for between-subject replication was weaker, with only a limited proportion of participants meeting the individual criterion for transfer.     

Antecedent reinforcement contingencies in the stimulus control of an auditory discrimination

In order to assess possible confounding of discriminative stimulus effects with those produced by the reinforcing stimulus, three groups of four rats each were trained for 45 hr on a variable-interval 1-min reinforcement program. Two groups were run on a multiple variable-interval extinction schedule in which the reinforcement stimulus (S^D) and the nonreinforcement stimulus (S^Δ) were two intensities of a 4-kHz (cps) tone separated by 40 or 10 db. The third group was run on a mixed schedule with a single intensity constantly present. The mixed-schedule animals showed no discrimination of the reinforcement program. Under the multiple schedule, the highest S^Δ rates were obtained after S^D intervals, regardless of the reinforcement availability in the S^D interval. These local rate variations in S^Δ were small in proportion to those produced by the S^D versus S^Δ intensities.     

Shaping of three-man teams on a multiple DRL-DRH schedule using collective reinforcement

Five three-man teams were conditioned to a multiple DRL-DRH schedule during five daily sessions of 3 hr each. The teams were conditioned on the basis of their cumulative response rate regardless of the contributions of individual members. Two individually conditioned Ss were run under a similar schedule for comparison. Although all teams demonstrated some differentiation of response rate under the two legs of the schedule, this difference was not achieved as rapidly, nor was it as stable, as the differentiation in rates achieved in individually conditioned Ss. Team members displayed a variety of response rates as a result of collective team conditioning. Often, individual response rates interfered with obtainment of team reinforcement. The individual team members displayed little S^D control in comparison with the individually conditioned Ss. In general the results suggest that collective reinforcement is highly inefficient in comparison with procedures employing individual feedback.     

Discrimination learning as a function of stimulus location along an auditory intensity continuum

Eight groups of rats were trained on an auditory intensity discrimination in which the discriminative stimuli were separated by 10 decibels (db). Four pairs of stimuli were selected from different regions along a 60–100 db (SPL) intensity continuum. Counterpart groups were trained on each stimulus pair, with the relative intensity positions of the reinforced stimulus (S^D) and the non-reinforced stimulus (S^Δ) reversed for the two groups. Discrimination acquisition curves were compared to determine whether stimuli separated by equal logarithmic units were of comparable “difficulty”, and to determine the relative effectiveness of an S^D serving as the more versus less intense member of a stimulus pair. It was concluded that: (1) When S^D is the more intense, auditory intensities of constant logarithmic separation are graded in “difficulty” along the intensity continuum; high intensity discriminative stimuli are most readily discriminated. When S^Δ is the more intense, this graded effect is not evident. (2) For a given continuum location, discrimination is inferior when S^Δ is the more intense. This effect is most pronounced at the high intensity end of the continuum and is chiefly attributable to differences in the rate of S^Δ responding.     

Nicotine vs. ethanol discrimination: Extinction and spontaneous recovery of responding

Studies regarding extinction and spontaneous recovery of the discriminative stimulus effects of drugs are limited. Eight rats were initially trained to discriminate nicotine (0.4 mg/kg) vs. ethanol (800 mg/kg). For four rats, itraperitaneal (IP) administrations of nicotine fifteen minutes prior to fifteen-minute training sessions served as a discriminative stimulus (S^D) for predicting food-reinforced lever pressing (VI-1 min). On other sessions ethanol functioned in predicting nonreinforcement (S^Δ). The stimulus roles of the drugs were counterbalanced for the remaining four rats. S^Δ and S^D sessions alternated quasi-randomly with two daily sessions at 1000 and 1400 hours. Discriminative control was not disrupted following ten extinction sessions under a non-drug/saline condition, but was disrupted following extinction sessions under the original training drugs. Instances of spontaneous recovery (SR) occurred throughout extinction under the drug condtions. There was no evidence for SR two weeks following extinction, but partial recovery four weeks following the final extinction phase. Contextual status (context renewal) had neither a restorative or disruptive impact on extiguished or discriminated responding, respectively. Theser results support and extend the limited number of other studies by demonstrating extinction and spontaneous recovery of responding discriminated bytwo distinct drugs. Some theoretical interpretations regarding history effects and training in the context of drug discrimination are entertained.     

Effect of prior Pavlovian discrimination training upon learning an operant discrimination

The effect of Pavlovian discrimination training with two stimuli upon subsequent learning of an operant discrimination involving those stimuli was studied. After preliminary lever press training, the lever was removed and thirsty rats received noncontingent pairings between S₁ (a tone or a clicker) and water reinforcements, whereas S₂ (a clicker or a tone) occurred always without reinforcement. This procedure presumably established S₁ as a positive CS for respondent behavior, whereas S₂ was established as an inhibitory CS. Following this training, the lever was reintroduced and the rats were trained on an operant (lever pressing) discrimination involving S₁ and S₂. For the Consistent Ss, S₁ was the S^D and S₂ the S^Δ in the operant discrimination; for the Reversed Ss, S₂ served as S^D and S₁ as S^Δ. The Consistent Ss learned the operant discrimination significantly faster than did the Reversed Ss. The result emphasizes the importance of respondents, conditioned to S^D and S^Δ, which modulate operant performance to these stimuli.