Stimulus factors in the training of prepositional usage in three autistic children

Language deficient, autistic children were trained to use the prepositions "in" and "on". Three subjects were exposed to conditions of training that differed in the method of employment of stimulus objects used to train prepositional usage. Two subjects were trained first with "ambiguous" stimuli, that is, the same stimulus objects were used for training both prepositions. The two subjects were then switched to a training condition with "non-ambiguous" stimulus objects, that is, objects used for training "in" were different than those used for training "on". The two subjects were then switched to the ambiguous stimulus condition and finally returned again to training with non-ambiguous stimuli (four conditions). A third subject began with training on non-ambiguous stimuli, was switched to an ambiguous condition and was then switched back to non-ambiguous stimuli (three conditions). The results for two of the three subjects indicated that accurate usage of the two prepositions was obtained only under training conditions with non-ambiguous stimuli. Results for the third subject suggested that initial training with non-ambiguous stimuli might enhance subsequent accurate responding with ambiguous stimuli.     

Evidence for perceptual learning in pigeons' recognition memory for pictures

In two experiments, pigeons were trained on a recognition memory task, which required them to refrain from responding to a picture seen earlier that day. They learned this discrimination without detectable reliance on cues relating to the sequence of positive and negative trials. In both experiments, performance was significantly better when the same restricted set of stimuli was used each day than when an entirely novel set of stimuli was used each day, and in the former case there was less evidence of any significant decline in performance with increases in the interval between first and second presentations of a stimulus. The results suggest a powerful perceptual learning effect.     

Control of responding by sounds of different quality: an evolutionary analysis.

Two experiments investigated the acquisition of discriminations between two acoustic stimuli of different quality (noise bursts vs. a 2-kHz pulsed signal) when features of the everyday environment were incorporated into the experiments. In Experiment 1, rats were trained, using food, to press a lever. Throughout all sessions, 5-s trials of noise bursts (the random stimulus) were presented, after variable intertrial intervals, through a remote speaker mounted outside the experimental enclosure. The noise burst occurred randomly with respect to reinforcement of lever pressing and had no programmed relationship to the animal's behavior. When lever pressing was established, the 2-kHz signal was presented through a speaker adjacent to the response lever according to a different set of variable intertrial intervals. A response in the presence of the 2-kHz signal terminated the trial and was reinforced. The 2-kHz signal acquired control of responding within the first few trials, whereas the random stimulus exerted no control of responding. In Experiment 2, rats were trained to press the lever in the presence of the 2-kHz signal presented through the adjacent speaker on a variable intertrial interval. After 14 sessions, 5-s trials of noise bursts (random stimulus) were presented through the remote speaker on the second variable intertrial interval. The random stimulus initially elicited exploratory behavior, which then rapidly declined. Subsequently, the random stimulus exerted no or weak control of responding. The introduction of the random stimulus had no effect on responding in the presence of the adjacent stimulus. In Experiments 3 and 4 the random stimulus was presented through the adjacent speaker, and the stimulus correlated with reinforcement was presented through the remote speaker. In both experiments, there was persistent control of responding by the random stimulus and slow development of control by the stimulus correlated with reinforcement. In Experiment 5, both stimuli were presented through the adjacent speaker. There was persistent control of responding by the random stimulus.     

Differential responding as a function of auditory stimulus intensity without differential reinforcement

Two groups of four rats each were trained to bar press on a variable-interval 2-min schedule. During training, either 3, 5, or 9 auditory stimuli of various intensities were randomly presented. A direct relationship between stimulus intensity and rate of responding was obtained, but it was more consistent in the group trained initially with three stimuli than for the group that started with nine stimuli. The results are related to the concept of stimulus intensity dynamism and the necessary conditions for the acquisition of stimulus control.     

Factors impacting emergence of behavioral control by underselected stimuli in humans after reduction of control by overselected stimuli

Stimulus overselectivity occurs when only one of potentially many aspects of the environment controls behavior. Adult participants were trained and tested on a trial-and-error discrimination learning task while engaging in a concurrent load task, and overselectivity emerged. When responding to the overselected stimulus was reduced by reinforcing a novel stimulus in the presence of the previously overselected stimulus in a second trial-and-error discrimination task, behavioral control by the underselected stimulus became stronger. However, this result was only found under certain circumstances: when there was substantial overselectivity in the first training phase; when control by the underselected stimulus in the first phase was particularly low; and when there was effective reduction in the behavioral control exerted by the previously overselected stimuli. The emergence of behavioral control by the underselected stimulus suggests that overselectivity is not simply due to an attention deficit, because for the emergence to occur, the stimuli must have been attended to and learned about in the training phase; but that a range of additional learning factors may play a role.     

On the role of covarying functions in stimulus class formation and transfer of function

This experiment investigated whether directly trained covarying functions are necessary for stimulus class formation and transfer of function in humans. Initial class training was designed to establish two respondent-based stimulus classes by pairing two visual stimuli with shock and two other visual stimuli with no shock. Next, two operant discrimination functions were trained to one stimulus of each putative class. The no-shock group received the same training and testing in all phases, except no stimuli were ever paired with shock. The data indicated that skin conductance response conditioning did not occur for the shock groups or for the no-shock group. Tests showed transfer of the established discriminative functions, however, only for the shock groups, indicating the formation of two stimulus classes only for those participants who received respondent class training. The results suggest that transfer of function does not depend on first covarying the stimulus class functions.     

Reinforcement by an imprinting stimulus versus water on simple schedules in ducklings

Ducklings (5 to 28 days old) were trained to peck a pole on fixed-ratio, fixed-interval, and multiple schedules using brief presentation of an imprinting stimulus as the response-contingent event. Other ducklings of the same age were trained similarly except that reinforcement consisted of access to water. With water reinforcement the typical fixed-ratio (“break-run”), fixed-interval (“scallop”), and multiple schedule response patterns were readily established and consistently maintained. With the imprinting stimulus these schedule effects were inconsistent in some subjects and virtually nonexistent in others, despite extended training. Schedule control with the imprinting stimulus was not improved by the use of a reinforcement signaling procedure which enhances responding reinforced by electrical brain stimulation on intermittent schedules. However, the overall rates of responding and the extinction functions generated after reinforcement with water versus the imprinting stimulus were comparable. These findings imply that control by temporal and discriminative stimuli may be relatively weak when a young organism's behavior is reinforced by presentation of an imprinting stimulus.     

Effect of signaling intertrial unconditioned stimuli in autoshaping

Context-unconditioned-stimulus (US) associations have been suggested as the mediator of the response decrement that occurs when extra USs are added to the intertrial intervals (ITIs) of an otherwise standard Pavlovian conditioning situation. The present autoshaping experiments were concerned with the effect of signaling those extra USs, since such signaling might be expected to lessen their ability to condition the context. Experiments 1 and 2 showed that signaling the ITI USs did reduce their detrimental effects on responding to the conditioned stimulus (CS). To determine whether that reduction was due to an impact of signaling on the target-CS-US association or on performance to the target-CS, Experiment 3 examined responding to differentially trained CSs in a common context, as well as responding to identically trained CSs in differentially trained contexts. Whether the CS was tested in a context of relatively high or low associative strength, more responding occurred to the CS trained with signaled, as compared with unsignaled, ITI USs; further, there was more responding to that CS in the more highly valued context. The pattern of results suggests that contextual value does interact with CS-US learning and may also affect performance to the CS.     

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.     

Free-operant escape-avoidance of noise by rats

A series of experiments was conducted to establish free-operant escape-avoidance responding in rats using noise as the stimulus. Naive rats did not acquire a bar-press response on an escape-avoidance of noise schedule. Similarly, free-operant responding established using escape-avoidance of shock was not maintained when noise was substituted for shock. Noise stimuli of 110 dB did maintain responding, but at a lower level than during training, when the noise stimuli had first been paired with shock. Noise stimuli of 97 dB and 87 dB were not effective under those same conditions. Additional rats were trained on a free-operant escape-avoidance schedule of shock and then exposed to a delayed conditioning procedure in which noise was the conditioned stimulus and shock was the unconditioned stimulus. When these subjects were then tested with noise alone, two of the three subjects conditioned and tested with 105-dB noise displayed escape-avoidance of noise, but none of the rats conditioned and tested at 97 dB displayed escape-avoidance of noise. The results suggest that free-operant escape-avoidance of noise can be demonstrated; however, only higher intensity noise stimuli that have been paired with shock are effective.     

The nature of control by spoken words over visual stimulus selection.

Eight retarded adolescents were trained to select one (a trained S+) of two visual stimuli in response to a spoken word (a trained word). Two different visual stimuli alternated randomly as the S-. To determine if the spoken work was merely a temporal discriminative stimulus for when to respond, or if it also specified which visual stimulus to select, the subjects were given intermittent presentations of untrained (novel) spoken words. All subjects consistently selected the trained S+ in response to the trained spoken word and selected the previous S- in response to the untrained spoken words. It was hypothesized that the subjects were responding away from the trained S+ in response to untrained spoken words, and control by untrained spoken words would not be observed when the trained S+ was not present. The two visual S- stimuli selected on trials of untrained spoken words were presented simultaneously. The untrained spoken words presented on these trials no longer controlled stimulus selections for seven subjects. The results supported the hypothesis that previous control by spoken words was due to responding away from the trained S+ in response to untrained spoken words.     

Characteristics of serial order learning in common marmosets (Callithrix jacchus)

We investigated the characteristics of serial order learning in common marmosets (Callithrix jacchus). Five marmosets were trained in a sequential responding task in which they were required to touch four graphic patterns in a given order (A→B→C→D) to obtain a reward. All five marmosets learned the task with over 65% accuracy. Shuffling the positions of B, C, and D immediately after the marmoset had correctly identified and selected the first stimulus (A) either decreased accuracy or lengthened response latency for the second stimulus (B). These results suggest that the marmosets planned the response to the second stimulus before they touched the first stimulus. In addition, when we presented a pair of stimuli (AB, AC, AD, BC, BD, and CD pairs), the marmosets responded to the stimuli in the pair in the appropriate order, according to the learned order (A→B→C→D). The analyses of first and second response latencies clearly demonstrated both the first-item and missing-item effects in task performance. Our data provide direct evidence that marmosets can learn the relative order of the four stimuli in a sequential responding task. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

The impact of arbitrarily applicable relational responding on evaluative learning about hypothetical money and shock outcomes

Evaluative learning comprises changes in preferences after co-occurrences between conditioned stimuli (CSs) and an unconditioned stimulus (US) of affective value. Co-occurrences may involve relational responding. Two experiments examined the impact of arbitrary relational responding on evaluative preferences for hypothetical money and shock outcomes. In Experiment 1, participants were trained to make arbitrary relational responses by placing CSs of the same size but different colours into boxes and were then instructed that these CSs represented different intensities of hypothetical USs (money or shock). Liking ratings of the CSs were altered in accordance with the underlying bigger/smaller than relations. A reversal of preference was also observed: the CS associated with the smallest hypothetical shock was rated more positively than the CS associated with the smallest amount of hypothetical money. In Experiment 2, procedures from Relational Frame Theory (RFT) established a relational network of more than/less than relations consisting of five CSs (A-B-C-D-E). Overall, evaluative preferences were altered, but not reversed, depending on (a) how stimuli had been related to one another during the learning phase and (b) whether those stimuli referred to money or shocks. The contribution of RFT to evaluative learning research is discussed.     

Blocking the development of stimulus control when stimuli indicate periods of nonreinforcement

To learn whether prior discrimination training based on one stimulus would block learning about a subsequently added stimulus, rats were first trained to press a bar on a variable-interval schedule of food reinforcement. Occasional stimuli were presented during which no reinforcement was available. Responding became suppressed in the presence of these stimuli. Stimuli could be noise, light, or a compound of noise plus light. A group trained with noise in Phase 1, then trained with the compound in Phase 2, showed less suppression to light in a subsequent test than a group that had the same compound training in Phase 2 but only variable-interval training in Phase 1. This showed that prior training with noise blocked the development of control by light during compound training. Two further groups showed that noise training following compound training did not have the same effect on control by light.     

Extending sequence-class membership with matching to sample

Three normal adults were first trained to point sequentially to each member of several pairs of visual stimuli. This baseline training established one class of stimuli to which subjects responded first, and another class of stimuli to which they responded second. Then, in a matching-to-sample procedure, baseline-sequence stimuli served as samples and new visual stimuli served as comparisons. Subjects were trained to choose one group of new comparisons when the sample was a "first" stimulus from the sequence baseline, and to choose the other new comparison stimuli when the sample was a "second" from the sequence baseline. When the new stimuli were then presented as pairs in the posttest, two subjects pointed to them in sequences predictable on the basis of the stimulus-class membership established during matching to sample. The failure of one subject to demonstrate sequential transfer was shown to be a consequence of the failure of the matching-to-sample procedure to establish stimulus classes. The production of sequences that were not directly trained suggested an empirical approach to the analysis of simple grammatical behavior.     

Assessing the role of alternative response rates and reinforcer rates in resistance to extinction of target responding when combining stimuli

Studies of behavioral momentum reveal that reinforcing an alternative response in the presence of a target response reduces the rate of target responding but increases its persistence, relative to training the target response on its own. Because of the parallels between these studies and differential‐reinforcement techniques to reduce problem behavior in clinical settings, alternative techniques to reduce problem behavior without enhancing its persistence are being explored. One potential solution is to train an alternative response in a separate stimulus context from problem behavior before combining the alternative stimulus with the target stimulus. The present study assessed how differences in reinforcement contingencies and rate for alternative responding influenced resistance to extinction of target responding when combining alternative and target stimuli in pigeons. Across three experiments, alternative stimuli signaling a response–reinforcer dependency and greater reinforcer rates more effectively decreased the persistence of target responding when combining alternative and target stimuli within the same extinction tests, but not when compared across separate extinction tests. Overall, these findings reveal that differences in competition between alternative and target responding produced by contingencies of alternative reinforcement could influence the effectiveness of treating problem behavior through combining stimulus contexts.     

Generalization of the disruptive effects of alternative stimuli when combined with target stimuli in extinction

Differential‐reinforcement treatments reduce target problem behavior in the short term but at the expense of making it more persistent long term. Basic and translational research based on behavioral momentum theory suggests that combining features of stimuli governing an alternative response with the stimuli governing target responding could make target responding less persistent. However, changes to the alternative stimulus context when combining alternative and target stimuli could diminish the effectiveness of the alternative stimulus in reducing target responding. In an animal model with pigeons, the present study reinforced responding in the presence of target and alternative stimuli. When combining the alternative and target stimuli during extinction, we altered the alternative stimulus through changes in line orientation. We found that (1) combining alternative and target stimuli in extinction more effectively decreased target responding than presenting the target stimulus on its own; (2) combining these stimuli was more effective in decreasing target responding trained with lower reinforcement rates; and (3) changing the alternative stimulus reduced its effectiveness when it was combined with the target stimulus. Therefore, changing alternative stimuli (e.g., therapist, clinical setting) during behavioral treatments that combine alternative and target stimuli could reduce the effectiveness of those treatments in disrupting problem behavior.     

A transfer of functions through derived arbitrary and nonarbitrary stimulus relations

During Experiments 1 and 2, subjects were trained in a series of related conditional discriminations in a matching-to-sample format (A1-B1, A1-C1 and A2-B2, A2-C2). A low-rate performance was then explicitly trained in the presence of B1, and a high-rate performance was explicitly trained in the presence of B2. The two types of schedule performance transferred to the C stimuli for all subjects in both experiments, in the absence of explicit reinforcement through equivalence (i.e., C1 = low rate and C2 = high rate). In Experiment 2, it was also shown that these discriminative functions transferred from the C1-C2 stimuli to two novel stimuli that were physically similar to the C stimuli (SC1 and SC2, respectively). For both these experiments, subjects demonstrated the predicted equivalence responding during matching-to-sample equivalence tests. In Experiments 3 and 4, the conditional discrimination training from the first two experiments was modified in that two further conditional discrimination tasks were trained (C1-D1 and C2-D2). However, for these tasks the D stimuli served only as positive comparisons, and ND1 and ND2 stimuli served as negative comparisons (i.e., C1 × ND1 and C2 × ND2). Subsequent to training, the negatively related stimuli (ND1 and ND2) did not become discriminative for the schedule performances explicitly trained in the presence of B1 and B2, respectively. Instead, the ND1 stimulus became discriminative for the schedule performance trained in the presence of B2, and ND2 became discriminative for the schedule performance trained in the presence of B1. All subjects from Experiment 4 showed that the novel stimulus SND1, which was physically similar to ND1, became discriminative for the same response pattern as that controlled by ND1. Similarly, SND2, which was physically similar to ND2, became discriminative for the same response pattern as that controlled by ND2. Subjects from both Experiments 3 and 4 also produced equivalence responding on matching-to-sample equivalence tests that corresponded perfectly to the derived performances shown on the transfer of discriminative control tests.     

The control of appetitive instrumental responding does not depend on classical conditioning to the discriminative stimulus

In Experiment I, rats were exposed to a classical relationship between a clicker-light compound and response-independent food. Conditioning to the light was blocked if the clicker had previously served as a classical signal for food, but not if it had been established as a discriminative stimulus for food-reinforced lever pressing. In Experiment II, a tone-light compound served as a discriminative stimulus for lever pressing. Control by the light was blocked if the tone was independently trained as a discriminative stimulus, but not if it was trained as a classical signal for response-independent food. These results suggest that discriminative stimuli do not come to control appetitive instrumental responding by virtue of their implicit classical relationship to the instrumental reinforcer.