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The capacity to exhibit generalized sameness-difference judgments is a hallmark of cognition that is regularly exhibited by humans. As yet, that capacity has not been well documented in New World monkeys such as the capuchin (Cebus apel/a). This article presents data obtained with 6 capuchi n monkeys with a variety of procedures that might lead to gEmeralized identity matching-to-sample (MTS) in this species, reporting part of a research program conducted to evaluate methods for assessing the species' relational learning capacity. Our working hypothesis is that past failures to demonstrate relational learning have been caused by procedural insufficiency rather than a lack of capacity. Thus far, 6 capuchin monkeys have been test, ed for generalized identity MTS. The apparatus was a touchscreen-equipped microcomputer-controlled experimental chamber. Eleven sets of 3 visual stimuli (black shapes on gray backgrounds) were used. The general procedure was comprised of 4 phases: (a) simple discriminations, (b) repeated shifts of simple discriminations, (c) identity MTS training, and (d) generalized identity MTS tests . Every subject was exposed to each of the phasE3s. Positive results

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.

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RESUMOO 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 paras 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 econduzidos. 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.Palavras-chave: equivalência de estímulos, pareamento ao modelo, discriminação simples, reforçamento específico, efeito de conseqüência específica, retardo mental ABSTRACT Initially, this paper makes some distinctions between simple and conditional discrimination concepts and points to tHuman participant performances often show evidence of learning untrained relations when conditional discrimination training between physically dissimilar stimuli is conducted. These emergent relations document equivalence 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 have suggested 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 had received 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.