Generalized Identity Matching to Sample after Multiple-Exemplar Training in Capuchin Monkeys.

A multiple-exemplar identity matching-to-sample baseline was established to encourage development of generalized IDMTS performances in three adult male capuchins. Mask (blank comparison) or Shuffled S- procedures were used to promote select (sample-S+) control in baseline relations and to assess stimulus control relations in generalized IDMTS tests. The IDMTS baseline comprised eight 3-stimulus sets or four 4-stimulus sets. Probe trials with new stimulus sets were substituted for baseline sets in successive testing sessions and subsequently converted to new baseline relations. All monkeys exhibited high accuracy on generalized IDMTS tests. A monkey who was given the Mask procedure in training and tests showed generalized IDMTS with select relations predominating. Two monkeys who were given training and testing with the Shuffled S- procedure performed somewhat better on Shuffled S- IDMTS test trials than on test trials that contained non-shuffled test IDMTS trials thus suggesting that exclusion of familiar nonmatching comparison stimuli from baseline in Shuffled S-test trials contributed to the higher accuracy scores with the former procedures. Development of select relations appeared to be a positive predictor of development of generalized IDMTS.

Restricted Stimulus Control in Stimulus Control Shaping with a Capuchin Monkey.

Teaching the first instances of arbitrary matching to sample to nonhumans can prove difficult and time consuming. Stimulus control relations may develop that differ from those intended by the experimenter - even when stimulus control shaping procedures are used. This paper reports efforts to identify sources of shaping program failure with a capuchin monkey. Procedures began with a baseline of identity matching. During subsequent shaping trials, compound comparison stimuli had two components - one identical to and another different from the sample. The identical component was eliminated gradually by removing portions across trials (i.e., subtracting stimulus elements). The monkey performed accurately throughout shaping. At a late stage in the program, probe tests were conducted: (1) arbitrary matching trials that had all elements of the identical comparison removed and (2) other trials that included residual elements. During the test, the monkey performed at low levels on the former trials and higher levels on the latter. These results suggested that higher accuracy was due merely to continued control by the residual elements: the target arbitrary matching relations had not been learned. Thus, it appears that procedures that gradually transform identity matching baselines into arbitrary matching can fail by inadvertently shaping restricted control by residual elements. Subsequent probes at the end of the shaping series showed a successful transfer of stimulus control from identity to arbitrary matching after further programming steps apparently overcame the restricted stimulus control.

Sample stimulus control shaping and restricted stimulus control in capuchin monkeys: a methodological note.

This paper reports use of sample stimulus control shaping procedures to teach arbitrary matching-to-sample to 2 capuchin monkeys (Cebus apella). The procedures started with identity matching-to-sample. During shaping, stimulus features of the sample were altered gradually, rendering samples and comparisons increasingly physically dissimilar. The objective was to transform identity matching into arbitrary matching (i.e., matching not based on common physical features of the sample and comparison stimuli). Experiment 1 used a two-comparison procedure. The shaping procedure was ultimately effective, but occasional high error rates at certain program steps inspired a follow-up study. Experiment 2 used the same basic approach, but with a three-comparison matching task. During shaping, the monkey performed accurately until the final steps of the program. Subsequent experimentation tested the hypothesis that the decrease in accuracy was due to restricted stimulus control by sample stimulus features that had not yet been changed in the shaping program. Results were consistent with this hypothesis, thus suggesting a new approach that may transform the sample stimulus control shaping procedure from a sometimes useful laboratory tool to a more general approach to teaching the first instance of arbitrary matching performances to participants who show protracted difficulties in learning such performances.

REVERSAL LEARNING SET AND FUNCTIONAL EQUIVALENCE IN CHILDREN WITH AND WITHOUT AUTISM.

To evaluate whether children with and without autism could exhibit (a) functional equivalence in the course of yoked repeated-reversal training and (b) reversal learning set, 6 children, in each of two experiments, were exposed to simple discrimination contingencies with three sets of stimuli. The discriminative functions of the set members were yoked and repeatedly reversed. In Experiment 1, all the children (of preschool age) showed gains in the efficiency of reversal learning across reversal problems and behavior that suggested formation of functional equivalence. In Experiment 2, 3 nonverbal children with autism exhibited strong evidence of reversal learning set and 2 showed evidence of functional equivalence. The data suggest a possible relationship between efficiency of reversal learning and functional equivalence test outcomes. Procedural variables may prove important in assessing the potential of young or nonverbal children to classify stimuli on the basis of shared discriminative functions.

A formação de classes de equivalência via pareamento por identidade e discriminação simples com conseqüências específicas para as classes / Equivalence class formation via identity matching to sample and simple discrimination with class-specific consequences

O desempenho de participantes humanos freqüentemente mostra aprendizagem de relações não diretamente ensinadas após o treino de discriminações condicionais entre estímulos fisicamente diferentes. Essas relações emergentes documentam a formação de classes de equivalência. O presente estudo investigou se conseqüências específicas para as classes (i.e., reforçadores específicos usados para cada classe potencial durante o treino) também integram as classes de equivalência. Vários estudos anteriores sugeriram que as conseqüências específicas podem integrar as classes, entretanto, o treino nesses estudos inclui pareamento arbitrário e pareamento por identidade.No presente estudo, duas crianças autistas foram submetidas apenas a treino de reversões de discriminações simples e pareamento por identidade com conseqüências específicas paras as classes potenciais. Então, testes de pareamento arbitrário foram conduzidos. O desempenho das crianças evidenciou a formação de classes nestes testes, a despeito de elas não terem experiência de treino de pareamento arbitrário. Adicionalmente, um dos participantes mostrou evidência de formação de classes após treino de reversões de discriminação simples somente. Esses resultados tanto demonstram que as conseqüências reforçadoras de fato se tornam parte das classes de equivalência, quanto dão suporte à idéia de que equivalência surge das contingências de reforçamento e não é baseada em habilidades lingüísticas.(AU)

Human participant performances often show evidence of learning untrained relations when conditional discrimination training between physically dissimilar stimuli is conducted. These emergent relations documentequivalence class formation. The current study investigated whether class-specific consequences (i.e. the specific reinforcers used for each potential class during training) also join the equivalence class. Several studies havesuggested they do so. However, training in those studies typically included arbitrary matching and identity matching baselines. In the current study, two autistic children were trained on simple discrimination reversals and identity matching with class specific consequences. They were then given arbitrary matching probes. Performances of both children initially showed evidence of class formation on these tests, despite the fact that neither hadreceived training on arbitrary matching. In addition, one of the participants showed evidence of class formation after simple discrimination reversal training alone. These results demonstrate that the reinforcing consequences do in fact become part of the stimulus equivalence class and provide support for the ideas that equivalence (1) arises from reinforcement contingency and (2) is not based upon language skills.(AU)

A note on select- and reject-controlling relations in the simple discrimination of capuchin monkeys (Cebus apella).

Controlling relations in the simple discrimination performances of capuchin monkeys (Cebus apella) were studied in two experiments using a blank-comparison procedure. The main goal was to determine whether monkeys would (a) select an S+ stimulus if another stimulus was substituted for the S- (indicating a select-controlling relation) and (b) reject an S- if another stimulus was substituted for S+ (indicating a reject-controlling relation). In experiment 1, two simple simultaneous discriminations were established, one of which was reversed repeatedly until rapid reversal learning was exhibited. During subsequent probe tests, some behavior was consistent with select- and reject-controlling relations, but there was also substantial variability. To control the variability, the procedures of experiment 2 were designed to establish select- and reject-control relations directly by training with the blank-comparison procedure. On subsequent probe trials, new stimuli were substituted for the blank comparison. Both animals exhibited consistent, reliable select- and reject-controlling relations. These experiments are the first to employ the blank-comparison procedure with non-human subjects. They also demonstrate a reliable method for generating select- and reject-controlling relations for experimental study.