Control by sample location in pigeons'' matching to sample.

Three experiments assessed the impact of sample location in pigeons' matching to sample. Experiments 1 and 2 demonstrated that after line or hue identity matching was acquired to high levels of accuracy with center-key samples, varying sample location across the three keys disrupted performances. The drop in accuracy occurred following both zero-delay and simultaneous training and was mostly confined to trials in which the sample appeared on a side key. Experiment 3 attempted to diminish control by location by training birds to match samples that could appear in any location prior to center-key sample training and moving-sample testing with another set of stimuli. In testing, all birds performed accurately on center-sample trials and on side-key sample trials in which the matching choice appeared on the center key. Accuracy was below chance, however, on side-key sample trials in which the matching choice appeared on the other side key. One implication of the persistent control by sample location in the three-key paradigm is that it precludes the possibility of symmetry because symmetry tests require a change in the locations at which samples and comparisons appear.     

Verbal self-reports of delayed matching to sample by humans

Undergraduates participated in two experiments to develop methods for the experimental analysis of self-reports about behavior. The target behavior was the choice response in a delayed-matching-to-sample task in which monetary reinforcement was contingent upon both speed and accuracy of the choice. In Experiment 1, the temporal portion of the contingency was manipulated within each session, and the presence and absence of feedback about reinforcement was manipulated across sessions. As the time limits became stricter, target response speeds increased, but accuracy and reinforcement rates decreased. When feedback was withheld, further reductions in speed and reinforcement occurred, but only at the strictest time limit. Thus, the procedures were successful in producing systematic variation in the speed, accuracy, and reinforcement of the target behavior. Experiment 2 was designed to assess the influence of these characteristics on self-reports. In self-report conditions, each target response was followed by a computer-generated query: “Did you earn points?” The subject reported by pressing “Yes” or “No” buttons, with the sole consequence of advancing the session. In some cases, feedback about reinforcement of the target response followed the reports; in other cases it was withheld. Self-reports were less accurate when the target responses occurred under greater time pressure. When feedback was withheld, the speed of the target response influenced reports, in that the probability of a “Yes” report increased directly with the speed of accurate target responses. In addition, imposing the self-report procedure disrupted target performance by reducing response speeds at the strictest time limit. These results allow investigation of issues in both behavioral and cognitive psychology. More important, the overall order in the data suggests promise for the experimental analysis of self-reports by human subjects.     

Transfer of pigeons' matching to sample to novel sample locations

This study examined the conditions under which conditional stimulus control by the sample stimuli in three-key matching-to-sample paradigms would generalize across the different possible sample locations. In Experiments 1 and 2, the samples appeared on the left and right side keys during initial training and then on the center key during testing. Transfer of pigeons' matching performances to the center-key samples was evident after both identity and symbolic matching training. In Experiment 3, pigeons trained on symbolic matching with two side-key samples or with a side-key and a center-key sample generally transferred their learned matching performances to those samples when they subsequently appeared in the remaining (novel) location. These results indicate that, when two-choice conditional discriminations are learned with more than one sample location, the visual characteristics of the sample per se predominantly come to control the pigeons' comparison choices. This finding encourages the use of the multiple-location training procedure as a way of reducing control by location, thus providing a more discriminating test of symmetry in animals.     

Programming stimuli in matching to sample

In these investigations, a “teaching machine” was used to train pre-school and first-grade children in a series of progressively difficult discrimination tasks, leading up to matching to sample. Such training was much more efficient than training in the final discrimination alone. The errors the subjects made were found to be a functon both of the differences between consecutive discriminations (the “size of the steps” in the program) and the length of training on each discrimination. Theoretical and practical implications of these findings are discussed.     

Formation of transitivity in conditional matching to sample by pigeons

Four homing pigeons were trained over 5 months in a zero-delay, “arbitrary” matching-to-sample procedure with sample and comparison stimuli presented on any of three response keys. Birds were also required to complete a fixed-ratio 10 requirement on both sample and comparison stimuli to terminate their presentation. The procedure resulted in the establishment of relations that were not specifically trained and that can be characterized by the property of transitivity in a stimulus equivalence context. This result was in contrast with the findings obtained from most previous research with nonhuman subjects.     

Chimpanzee responding during matching to sample: control by exclusion

Three chimpanzees performed a computerized matching-to-sample task in which samples were photographs of items and comparison stimuli were geometric symbols called lexigrams. In Experiment 1, samples were either defined (i.e., they represented items that were associated already with a specific lexigram label by the chimpanzees) or undefined (i.e., they did not have an already learned association with a specific lexigram). On each trial, the foil (incorrect) comparison could be either a defined or an undefined lexigram. All 3 chimpanzees selected the correct comparison for undefined samples at a level significantly better than chance only when the foil comparison was defined. In Experiment 2, three comparisons were presented on each trial, and in Experiment 3, four comparisons were presented on each trial. For Experiments 2 and 3, the foil comparisons consisted of either defined or undefined comparisons or a mixture of both. For these two experiments, when the chimpanzees were presented with an undefined sample, they typically made selections of only undefined comparisons. These data indicate that the chimpanzees responded through use of exclusion. A final experiment, however, indicated that, despite the use of exclusion to complete trials with undefined samples correctly, the chimpanzees did not learn new associations between undefined samples and comparisons.     

Sample-specific ratio effects in matching to sample

In a symbolic matching-to-sample task, pigeons were trained using sample-specific, fixed-ratio “observing responses.” Subsequently, in a mixed condition, each sample was presented equally often with each ratio requirement, i.e., the ratios were no longer correlated with the samples. In a second experiment, pigeons were trained initially in the mixed condition and subsequently shifted to the sample-specific condition in which the required ratios were correlated with the samples. Results of both experiments suggested joint control of choices by ratio value and by the exteroceptive stimuli. The discriminative properties of the ratios appeared to outweigh absolute ratio-size effects.     

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.     

Learning mechanisms in matching to sample.

A model system and an experiment on early learning and decision processes in matching-to-sample and oddity-from-sample tasks are presented. The model system is based, in part, on videotaped records of pigeons' looking responses before they chose 1 of 2 comparison stimuli. In order to see the wavelength stimuli recessed behind the pecking keys, the pigeons had to move in front of them. Although there were slight increases in the acceptance probability with switches between the stimuli before a choice response, the overall decision strategy was close to a Markov choice process in which choice proportions could be predicted by the product of each rejection probability and the final acceptance probability. Learning involved learning to discriminate rather than learning to adopt a stricter criterion for an acceptable sample match.     

Serial order effects in auditory discrimination by oddity and matching to sample

The oddity method and several matching-to-sample procedures were used for frequency and intensity discrimination by adult Ss. For all sequence tasks involving three choices, the Ss employed a decision strategy which resulted in a pattern of correctness that differed from the pattern of discriminability among the choice sounds. It was concluded that the use of signal detection theory for analysis of results had added an important dimension to the study, and it was recommended that this method of analysis be used in further attempts to relate sequential processes to various forms of verbal impairment.     

Acquisition of matching to sample via mediated transfer

Two severely retarded Down's-syndrome boys learned a matching-to-sample performance through mediated transfer. The transfer paradigm involved three sets of stimuli, one auditory set (A) and two visual sets (B and C). The subjects were taught directly to do B-A and C-B matching, but experienced no direct association between C and A. They acquired the ability to do C-A matching without having been taught that performance directly. They also learned indirectly to name some of the visual stimuli, but naming was apparently not the mediator in the emergent C-A matching. The use of words and letters as stimuli highlighted the possible relevance of mediated associations in the indirect acquisition of elementary reading comprehension and oral reading. The acquisition of matching via mediated transfer also raised some new considerations concerning the role of coding responses in arbitrary matching to sample.     

Covert verbal mediation in arbitrary matching to sample

Covert verbal mediation was examined in an arbitrary matching‐to‐sample (MTS) preparation with a high‐verbal group (college students) and a low‐verbal group (adults with intellectual disabilities). Arbitrary relations were established between nonsense words, visual symbols, objects, and hand signs. Task difficulty was balanced for the groups based on errors during acquisition. All participants experienced a hand sign condition, and three MTS conditions each with a unique configuration of the comparison array: fixed location, random location, and all symbols the same. The same symbol condition was designed to impede a participant's ability to label individual symbols. The results showed that disrupting labeling adversely affected MTS performance for high‐verbal participants, but not for low‐verbal participants. The data suggest that high‐verbal participants depended on mediating verbal behavior and joint control to assist them in finding the correct comparison stimulus. Low‐verbal participants could not benefit from verbal mediating variables and likely relied on unmediated contingencies, or some form of nonverbal mediation. For the high‐verbal group, 19 different putative emergent relations were identified as occurring at various stages of acquisition between the sample stimulus and the selection response. These emergent relations likely provided supplementary sources of stimulus control that participated in evoking MTS selection behavior.     

A sorting‐to‐matching method to teach compound matching to sample

Individuals with developmental disabilities may fail to attend to multiple features in compound stimuli (e.g., arrays of pictures, letters within words) with detrimental effects on learning. Participants were 5 children with autism spectrum disorder who had low to intermediate accuracy scores (35% to 84%) on a computer‐presented compound matching task. Sample stimuli were pairs of icons (e.g., chair–tree), the correct comparison was identical to the sample, and each incorrect comparison had one icon in common with the sample (e.g., chair–sun, airplane–tree). A 5‐step tabletop sorting‐to‐matching training procedure was used to teach compound matching. The first step was sorting 3 single pictures; subsequent steps gradually changed the task to compound matching. If progress stalled, tasks were modified temporarily to prompt observing behavior. After tabletop training, participants were retested on the compound matching task; accuracy improved to at least 95% for all children. This procedure illustrates one way to improve attending to multiple features of compound stimuli.     

Assessing control by elements of complex stimuli in delayed matching to sample.

A series of six experiments examined delayed identity matching-to-sample performances of subjects with mental retardation. The stimuli were either one or two simultaneously displayed forms. When the reinforcement contingencies required that only one form exert discriminative control, all subjects achieved high accuracy scores. However, accuracy scores were substantially lower when the contingencies required discriminative control by two forms, suggesting restricted stimulus control. The decline in matching accuracy appeared to reflect selective losses of conditional control by sample stimuli and shifts in control to features of the comparison stimulus displays. The experiments suggest improved techniques for assessing control by complex stimuli and for evaluating the effects of procedures that seek to broaden restricted stimulus control. The results challenge interpretations based on stimulus-generalization decrement or shared attention.     

Recombinative generalization of subword units using matching to sample

The purpose of the current study was to develop and test a computerized matching-to-sample (MTS) protocol to facilitate recombinative generalization of subword units (onsets and rimes) and recognition of novel onset-rime and onset-rime-rime words. In addition, we sought to isolate the key training components necessary for recombinative generalization. Twenty-five literate adults participated. Conditional discrimination training emerged as a crucial training component. These findings support the effectiveness of MTS in facilitating recombinative generalization, particularly when conditional discrimination training with subword units is used.