ACQUISITION OF INTRAVERBAL BEHAVIOR: TEACHING CHILDREN WITH AUTISM TO MAND FOR ANSWERS TO QUESTIONS

Four boys with autism were taught via echoic prompting and constant prompt delay to mand for answers to questions by saying “I don't know please tell me” (IDKPTM). This intervention resulted in acquisition of the IDKPTM response for all 4 participants and in acquisition of correct answers to most of the previously unknown questions for 2 participants. For 1 participant, tangible reinforcement resulted in increased frequency of correct answers, and direct prompting of correct answers was eventually conducted for the final participant. The IDKPTM response generalized to untargeted unknown questions with 3 participants. Results of person and setting generalization probes varied, but some generalization eventually occurred for all participants following additional training or interspersal of probe trials with training trials.     

Navigation in the Morris swim task as a baseline for drug discrimination: a demonstration with morphine

A morphine versus saline discrimination was demonstrated using the Morris swim task as the behavioral baseline. The apparatus was a large circular pool filled with water made opaque by floating polypropylene pellets. Rats were placed in the tank in randomly selected locations (12 trials per session) and could escape by swimming to a platform submerged 2 cm below the surface. Morphine (5.6 mg/kg) or saline was injected prior to training sessions. The position of the platform in a given session depended on the drug condition, thus forming the basis for discriminative responding. Three of the 4 rats acquired the discrimination, as evidenced by direct swims to the condition-appropriate platform. Generalization probe sessions were conducted following acquisition. Probe sessions were preceded by injections of morphine (0, 1.0, 3.0, 5.6, or 10.0 mg/kg) and involved placing the rat in the pool for 1 min without a platform. Swim patterns revealed a gradient, with probe swimming more concentrated in the area of the morphine platform position after higher morphine doses. In addition, dose-dependent increases in the likelihood of swimming first to the morphine-associated platform location were obtained. These results illustrate the generality of drug discrimination across different behavioral procedures, and of particular interest with respect to spatial learning, demonstrate interoceptive stimulus control of navigation.     

Reinforcement of probe responses and acquisition of stimulus control in fading procedures

Stimulus control of pigeons' key pecking was transferred from colors to lines by the method of stimulus fading. Fading was conducted with the addition of probes consisting of the line stimuli presented alone at each fading level. Probe responding was used to measure stimulus-control acquisition by the lines. Effects of reinforcement and nonreinforcement of probe responding upon acquisition of stimulus control were assessed using a single-organism repeated-acquisition design in which three fades were conducted serially. Probe responding was not reinforced in the first and third fade but was in the second. Reinforcement of probe responding substantially reduced the number of fading levels needed to complete fading. The outcome of a control experiment ruled out the possibility of accounting for these results in terms of the specific stimuli used in each fade or in terms of the sequential exposure to the three discriminations. Although probes permitted measurement of stimulus-control acquisition in fading, a measurement/acquisition interaction was also present.     

Effects of daily probing on acquisition of instructive feedback responses

This study evaluated the effects of daily probes of instructive feedback stimuli on students' acquisition of two types of instructive feedback responses. Four students, two with disabilities, participated and were taught four sets of behaviors, two sets received daily probes and two sets did not. A modification of the multiple probe design across behaviors was used. The findings indicate that students acquired their target behaviors rapidly and maintained correct responding during subsequent probe conditions. Students also acquired both types of instructive feedback and maintained it across subsequent probe conditions. The daily probes of the instructive feedback stimuli did not appear to enhance acquisition or maintenance of the instructive feedback responses, but students appeared to acquire the instructive feedback responses while learning their target behaviors. The implications of this study for understanding how students learn instructive feedback responses and for practice are discussed.     

TEACHING RECEPTIVE NAMING OF CHINESE CHARACTERS TO CHILDREN WITH AUTISM BY INCORPORATING ECHOLALIA

The facilitative effect of incorporating echolalia on teaching receptive naming of Chinese characters to children with autism was assessed. In Experiment 1, echoing the requested character name prior to the receptive naming task facilitated matching a character to its name. In addition, task performance was consistently maintained only when echolalia preceded the receptive manual response. Positive results from generalization tests suggested that learned responses occurred across various novel conditions. In Experiment 2, we examined the relation between task difficulty and speed of acquisition. All 3 participants achieved 100% correct responding in training, but learning less discriminable characters took more trials than learning more discriminable characters. These results provide support for incorporating echolalia as an educational tool within language instruction for some children with autism.     

Receptive training of adjectival inflections in mental retardates

A generalized discrimination of /er/ and /est/ suffixes as labels for stimuli exemplifying comparative or superlative relationships was established in three institutionalized retardates through differential reinforcement. The subjects were first taught correct pointing in response to opposite adjectives (e.g., "big-small") presented as labels for simple visual stimuli, and then taught each of the comparatives, or each of the superlatives possible for those opposites (e.g., "big-bigger" and "small-smaller", or "big-biggest" and "small-smallest"). As training proceeded, novel combinations of the training stimuli were presented as unreinforced probes to display any developing generalization of the training. As training of comparative discrimination proceeded, correct pointing response to comparative probes was high, but correct response to superlative probes was low. When training of superlative discriminations replaced training of comparatives, correct response to superlative probes increased, and correct response to comparative probes remained high.     

Effects of ratio reinforcement schedules on discrimination performance by Japanese monkeys

In Experiment 1, Japanese monkeys were trained on three conditional position-discrimination problems with colors as the conditional cues. Within each session, each problem was presented for two blocks of ten reinforcements; correct responses were reinforced under continuous-reinforcement, fixed-ratio 5, and variable-ratio 5 schedules, each assigned to one of the three problems. The assignment of schedules to problems was rotated a total of three times (15 sessions per assignment) after 30 sessions of acquisition training. Accuracy of discrimination increased to a moderate level with fewer trials under CRF than under ratio schedules. In contrast, the two ratio schedules, fixed and variable, were more effective in maintaining accurate discrimination than was CRF. With further training, as asymptotes were reached, accuracy was less affected by the schedule differences. These results demonstrated an interaction between the effects of reinforcement schedules and the level of acquisition. In Experiment 2, ratio sizes were gradually increased to 30. Discrimination accuracy was maintained until the ratio reached 20; ratio 30 strained the performance. Under FR conditions, accuracy increased as correct choice responses cumulated after reinforcement.     

A new approach to the formation of equivalence classes in pigeons

Four pigeons were given simultaneous discrimination training with visual patterns arbitrarily divided into two sets, with the stimuli in one set designated A1, B1, C1, and D1 and those in the other set designated A2, B2, C2, and D2. In sequentially introduced training phases, the pigeons were exposed to a series of reversals to establish AB and then CD equivalences. In subsequent testing sessions, a subset of stimuli from one set served as positive stimuli and those from the other set as negative stimuli on training trials, and transfer of the reinforced relation to other members of the sets was tested with nonreinforced probe trials. The pigeons were trained further on AC and BD equivalences and then were tested for the emergence of untrained AD and BC equivalences. Two of the 4 pigeons exhibited the emergence of one of these untrained equivalences, evidence for the emergence of transitive relations. This finding suggests that the pigeons established three-member functional equivalence classes by incorporating separately trained multiple equivalence relations. Repeated reversal training and probe testing enabled us to explore the formation and expansion of functional equivalence classes in pigeons.     

Acquisition of matching-to-sample performance in rats using visual stimuli on nose keys.

Steady and blinking white lights were projected on three nose keys arranged horizontally on one wall. The procedure was a conditional discrimination with a sample stimulus presented on the middle key and comparison stimuli on the side keys. Three rats acquired simultaneous "identity matching." Accuracy reached 80% in about 25 sessions and 90% or higher after about 50 sessions. Acquisition progressed through several stages of repeated errors, alteration between comparison keys from trial to trial, preference of specific keys or stimuli, and a gradual lengthening of strings of consecutive trials with correct responses. An analysis of the acquisition curves for individual trial configurations indicated that the matching-to-sample performance possibly consisted of separate discriminations.     

Acquisition of stimulus control while introducing new stimuli in fading.

After establishing discrimination between a red positive stimulus and a green negative stimulus, the lowest intensity colors that restricted all responding to the positive stimulus were determined. Then, two new white lines differing in terms of line orientation were each superimposed on one of the colors and were increased in intensity. Thereafter, the intensity of the colors was decreased and eventually eliminated. Probe stimuli consisting of the lines presented against dark backgrounds were presented before each change of stimulus intensity, and probe responding was used to assess the control acquired by various dimension of the new stimuli during the course of fading. The lines acquired control of responding while they were being introduced, and control was strengthened as the colors were attenuated. Such a locus of acquisition was attributed to the starting intensity of the original controlling stimuli and was explained in terms of stimulus blocking. Finally, using probes while introducing the new stimuli enhanced the acquisition of control by the new stimuli.     

Quokkas (Setonix brachyurus) demonstrate tactile discrimination learning and serial-reversal learning

Two male quokkas (Setonix brachyurus: a herbivorous macropod marsupial) were trained to discriminate pairs of stimuli in the laboratory. Quokkas indicated their choice by pulling on 1 of 2 simultaneously presented cords. The quokkas' discrimination abilities were tested on 6 tactile and 6 visual discrimination tasks. Correct responses were rewarded with food. For both quokkas, all tactile tasks were learned to a criterion of 75% correct in up to 4 20-trial sessions. No visual task maintained criterion performance in 4 sessions. One tactile discrimination was reversed 10 times. After the 1st reversal, the error rate declined sharply and fell to a level well below the initial discrimination.     

Optional-shift behaviour in rats: a novel procedure for assessing attentional processes in discrimination learning

A novel, optional-shift procedure was used to assess changes in the attention paid to stimuli that occur over the course of discrimination learning. In Phase 1, rats were trained on a conditional instrumental discrimination using audiovisual stimulus compounds; one stimulus dimension (auditory or visual) was relevant to the solution of the discrimination, the other was irrelevant. In Phase 2, all animals received three sessions of training with novel audiovisual compounds where both dimensions were equally diagnostic. Results from probe test trials indicated that, during Phase 2, animals learnt most about cues belonging to the stimulus dimension that was relevant during Phase 1. These results suggest that over the course of discrimination learning there was an increase in the amount of attention paid to relevant stimuli and/or a decrease in the attention paid to irrelevant stimuli.     

Optional-shift behaviour in rats: A novel procedure for assessing attentional processes in discrimination learning

A novel, optional-shift procedure was used to assess changes in the attention paid to stimuli that occur over the course of discrimination learning. In Phase 1, rats were trained on a conditional instrumental discrimination using audiovisual stimulus compounds; one stimulus dimension (auditory or visual) was relevant to the solution of the discrimination, the other was irrelevant. In Phase 2, all animals received three sessions of training with novel audiovisual compounds where both dimensions were equally diagnostic. Results from probe test trials indicated that, during Phase 2, animals learnt most about cues belonging to the stimulus dimension that was relevant during Phase 1. These results suggest that over the course of discrimination learning there was an increase in the amount of attention paid to relevant stimuli and/or a decrease in the attention paid to irrelevant stimuli.     

AN ANALYSIS OF ERROR-CORRECTION PROCEDURES DURING DISCRIMINATION TRAINING

Mechanisms involved in error-correction procedures during behavioral acquisition were examined. Seven developmentally delayed subjects participated in match-to-sample discrimination training, consisting of three conditions arranged in a multielement design. Correct responses in all conditions were followed by praise and either food or pennies. In the baseline condition (differential reinforcement), an error produced no consequences. In the practice condition, an error was followed by repetition of the trial until a correct response occurred. In the avoidance condition, an error was followed by additional trials consisting of irrelevant stimuli; this condition separated the effects of repeated exposure to the same task from those of negative reinforcement, both of which existed in the practice condition. All 7 subjects made noticeable progress in the baseline condition. However, 5 of the 7 performed better in one of the error-correction conditions: 2 performed better in the practice condition, and 3 performed better in the avoidance condition. These data indicate that error-correction procedures may serve multiple functions and suggest that the practice requirement in this study included both avoidance and stimulus control components. More generally, the data indicate that additional control procedures should be included in acquisition studies to identify the relevant behavioral mechanism(s).     

Acquisition and retention of a letter-detection skill

In two experiments, we examined the acquisition and retention of a letter-detection skill with a consistent-mapping procedure. In Experiment 1, subjects were trained from 0 to 4 sessions at detecting the letter H in displays containing random letters, and retesting occurred after a 1-month delay. Performance improved and in some cases became more automatic, and the performance level was maintained over the retention interval. When tested with a prose passage, the high error rate on the word THE was eliminated after training and after the retention interval, regardless of the amount of training. In Experiment 2, two subjects were given 12 sessions of training followed by a retention test 6 months later. For 1 subject there was also a retention test 15 months after acquisition. Performance improved dramatically with training, and substantial but not complete automaticity was achieved. Performance on the retention tests was close to the final acquisition level. The surprising lack of forgetting in this study was contrasted with the substantial forgetting typically found in studies of verbal learning.     

Conditional discrimination in mentally retarded subjects: programming acquisition and learning set.

In Experiment 1, 3 subjects with retardation were exposed to two visual-visual arbitrary matching-to-sample problems each day. One conditional discrimination was presented under trial-and-error conditions, and the other was presented under a component training procedure. The latter began by establishing the comparison discrimination and its rapid reversal. The successive discrimination between the sample stimuli was established through differential naming. Then, sample naming was maintained in conditional discrimination sessions in which the same sample was presented in blocks of consecutive trials. Block size was decreased across sessions until sample presentation was randomized as in trial-and-error training (but with naming maintained). Two subjects initially learned only with component training. The performance of the 3rd subject was inconsistent across conditional discriminations. One of the successful subjects ultimately learned rapidly and consistently with trial-and-error procedures. Experiment 2 sought to demonstrate learning set in the other 2 subjects. Elements of the component training procedure were withdrawn over successive conditional discriminations. Ultimately, 1 subject nearly always learned under trial-and-error conditions, and the other learned under trial-and-error conditions combined with differential sample naming.     

Effect of observing response requirements to sample and comparison stimuli on the establishment of reject control (sample/S- relations)

The establishment of sample/S- relations (or reject control) during conditional discrimination training (AB, BC) affects transitivity (AC), equivalence (CA) and reflexivity (AA, BB, CC) test outcomes. The present study parametrically evaluated the effects of different observing patterns to comparison stimuli on the establishment of reject control during baseline conditional relation training. A matching-to-sample with observing requirements (MTS-OR) procedure was implemented during AB and BC conditional discrimination training. During training, the participants were required to observe the sample and incorrect comparison on every trial before responding. In addition, the participants were divided into three groups that differed regarding the percentage of training trials on which they were prevented from observing the correct comparison stimuli: 25%, 50%, and 75%. Once the mastery criteria were achieved during training, transitivity (AC), symmetry (BA, CB), equivalence (CA), and reflexivity (AA, BB, CC) tests were conducted with all comparison stimuli visible from the beginning. The results suggest that the number of errors during transitivity, equivalence, and reflexivity tests progressively increased as participants were prevented from observing the correct comparison on a greater number of trials during training. Symmetry test results, however, were not affected by the experimental manipulation. Moreover, the number of participants showing reject-control patterns during tests slightly increased and the number of participants showing select-control patterns decreased as a function of the number of trials on which the participants were prevented from observing the correct comparison. Thus, we suggest that observing patterns during training is a relevant variable that affects equivalence test outcomes.     

An investigation of the differential-outcomes effect within sessions

The differential-outcomes effect is manifest as more accurate performance of a delayed conditional discrimination when alternative choice responses are followed by different reinforcers than when they are followed by the same reinforcer. In Experiment 1, a differential-outcomes effect was demonstrated within sessions by signaling the duration of food access for correct responses with stimuli appearing in conjunction with the sample stimuli. The delayed matching-to-sample performance of 5 pigeons was more accurate when green choice responses (matching a green sample) were followed by 3.5-s food access and red choice responses (matching a red sample) were followed by 0.5-s food access (different-outcome trials) than when the correct choice responses were both followed by 1.5-s reinforcers (same-outcome trials). In Experiment 2, the acquisition of this differential-outcomes effect was characterized by a progressive decrease in rate of forgetting on different-outcome trials and no change in rate of forgetting on same-outcome trials. In addition, accuracy at the shortest delay intervals for both different-outcome and same-outcome trials increased over acquisition, but to a greater extent for different-outcome trials. These data suggest that both memorial and attentional (time-dependent and time-independent) factors contribute to the differential-outcomes effect.     

Olfactory discrimination learning in mice lacking the fragile X mental retardation protein

An automated training system was used to compare the behavior of knockout (KO) mice lacking the fragile X mental retardation protein with that of wild-type (WT) mice (C57Bl/6 strain) in the acquisition and retention of olfactory discriminations. KO and WT mice did not differ in the acquisition of a four-stage nose poke shaping procedure. In two separate experiments, mutant mice required substantially more training to acquire a series of novel olfactory discrimination problems than did control mice. The KO mice required significantly more sessions to reach criterion performance, made significantly more errors during training, and more often failed to acquire discriminations. Both KO and WT mice showed similar error patterns when learning novel discriminations and both groups showed evidence of more rapid learning of later discriminations in the problem series. Both groups showed significant long-term memory two or four weeks after training but WT and KO mice did not differ in this regard. A group of well-trained mice were given training on novel odors in sessions limited to 20–80 trials. Memory of these problems at two day delays did not differ between WT and KO mice. Tests using ethyl acetate demonstrated that WT and KO mice had similar odor detection thresholds.     

Effects of amphetamine-CNS depressant combinations and of other CNS stimulants in four-choice drug discriminations

Three pigeons were trained to discriminate among 5 mg/kg pentobarbital, 2 mg/kg amphetamine, a combination of these two drugs at these doses, and saline using a four-choice procedure (amphetamine-pentobarbital group). Three other pigeons were trained to discriminate among 5 mg/kg morphine, 2 mg/kg methamphetamine, a combination of these two drugs at these doses, and saline (methamphetamine-morphine group). After 10 to 13 months of training, the pigeons averaged more than 90% of their responses on the appropriate key during training sessions. In subsequent testing, dose-response curves were determined for the individual drugs, for a wide range of dose combinations of the training drugs, and for two drugs to which the pigeons had not been exposed previously (pseudoephedrine and nicotine). After low test doses of the training drugs, pigeons responded on the saline key. As the dose increased, responding on the key associated with that drug during training sessions increased. When training drugs were combined at doses that were not discriminable when given alone, responding occurred on the saline key. When a discriminable dose of one training drug was combined with a nondiscriminable dose of the other training drug, responding occurred on the key associated with the discriminable dose. When both drugs were given at discriminable doses, responding almost always occurred on the drug-combination key. The response-rate decreasing effects of pentobarbital and amphetamine were mutually antagonized when the drugs were combined, but the rate-decreasing effects of morphine and methamphetamine were not. After low doses of pseudoephedrine and nicotine, pigeons in both groups responded on the saline key. After higher doses of pseudoephedrine and nicotine, responding in the amphetamine-pentobarbital group occurred primarily on the amphetamine key. In the methamphetamine-morphine group, higher doses of pseudoephedrine and especially nicotine engendered more responding on the combination key than had occurred in the other group. The four-choice procedure can reveal subtle effects in the discrimination of individual drugs and drug combinations that are not apparent with procedures offering fewer response alternatives.