Blank-comparison matching-to-sample reveals a false positive symmetry test in a capuchin monkey

A positive symmetry test result was obtained with a capuchin monkey that had previously exhibited virtually errorless AB and BA arbitrary matching-to-sample (MTS) with different stimuli. The symmetry test (BA) followed the acquisition of a new AB relation. It seemed possible, however, that the positive result could have occurred through the exclusion of previously defined comparison stimuli and not because the new AB and BA relations had the property of symmetry. To assess this possibility, a blank-comparison MTS procedure was implemented that permitted the separate assessment of select and reject (i.e., exclusion) control with both baseline and BA matching relations. In this assessment, the monkey did not exhibit reliable BA matching when exclusion was not possible, thus showing that the symmetry result was a false positive. However, the study demonstrated the feasibility of using a blank comparison MTS procedure with capuchins. The present results may set the stage for more successful methodology for establishing desired forms of relational stimulus control in capuchins and ultimately improving the assessment of relational learning capacity in that species, other nonhuman species, and nonverbal humans...

Expansão de repertório de relações arbitrárias em Sapajus sp. via exclusão / Expanding arbitrary relations repertoire by exclusion in Sapajus sp

O procedimento de exclusão pode expandir repertório relacional arbitrário de crianças, em condições de aprendizagem sem erros. Embora a escolha por exclusão esteja presente em diversas espécies não humanas, ela nem sempre resulta na aprendizagem de novas relações. O objetivo deste trabalho foi verificar a escolha por exclusão em um macaco-prego e a aquisição das novas relações arbitrárias como um resultado do contexto de exclusão. O sujeito apresentava um repertório de 5 relações arbitrárias A-B e suas simétricas B-A adquirido em estudo prévio, em um procedimento de pareamento ao modelo com atraso, envolvendo cinco ou mais escolhas como comparações. Neste estudo, usando o procedimento de pareamento ao modelo com duas escolhas, novas relações arbitrárias A-C foram introduzidas, usan-do-se estímulos B como S-, para verificar exclusão. O sujeito respondeu corretamente nas tentativas de exclusão excluindo o estímulo B e escolhendo o estímulo C. A aprendizagem das novas relações A-C foi avaliada em tentativas compostas apenas por comparações do Conjunto C, e o sujeito respondeu incorretamente nessas tentativas. Um treino com comparação vazia visando estabelecer controle por seleção e rejeição nas relações A-C não foi efetivo em gerar relações de controle por seleção. Em estudos futuros serão usadas mais de duas escolhas por tentativa no treino A-C, em contexto de exclusão, visando obter a aprendizagem das novas relações.

The procedure of exclusion may expand children's repertoire of arbitrary relations resulting in errorless learning, but although choice by exclusion has been reported in a variety of species, it is not followed by learning of the new relations. The objective of this paper was to verify if capuchins would choose by exclusion, and if they subsequently would acquire the new arbitrary relations as outcome of exclusion. The capuchin monkey had previously acquired a repertory of 5 A-B and their symmetric B-A arbitrary relations in delayed-matching to-sample (DMTS) with five or more choices. Using a two-choice DMTS, new A-C relations were introduced using non paired B stimuli as S- to verify exclusion. The subject excluded non paired B and chose the new C stimuli. However, performance was disrupted in trials with only C stimuli as comparisons; training with a blank stimulus substituting either comparison in turns was ineffective. Further studies using trials with more than two comparison stimuli will verify arbitrary relations' learning in capuchins after exclusion.

Comparison of two computerized procedures for the assessment of color discrimination in Cebus apella

Color vision consists of the discrimination of objects based on their spectral composition. Among primates, the majority of Platyrrhini monkeys are estimated to have polymorphic and sex-linked dichromacy. The objective of this study was to compare the results produced by different equipment and software for the assessment of tri- and dichromatic conditions in one male and two female Cebus apella. Three experiments were programmed. In Experiment 1, verifying the trichromatic condition of one female subject and dichromatic condition of the remainder of the subjects was possible using an adapted version of the Cambridge Colour Test. Experiment 2 confirmed the results of Experiment 1 using a different array of stimuli of the same test. Experiment 3, which produced results similar to Experiment 2, consisted of a test developed for a standard computer system using stimuli with color properties similar to the ones used in the previous experiment. Favorable conditions for the assessment of color vision in Platyrrhini can be built with low-cost equipment and software. Once data have been gathered with additional subjects and new stimulus arrangements have been tested and confirmed, the procedure can be used for the evaluation of other Platyrrhini species for which behavioral color discrimination data are currently lacking.

Discrimination of complex visual stimuli in Cebus apella: identity matching with pictures

Do capuchin monkeys respond to photos as icons? Do they discriminate photos of capuchin monkeys’ faces? Looking for answers to these questions we trained three capuchin monkeys in simple and conditional discrimination tasks and tested the discriminations when comparison stimuli were partially covered. Three capuchin monkeys experienced in simultaneous simple discrimination and IDMTS were trained with repeated shifts of simple discriminations (RSSD), with four simultaneous choices, and IDMTS (1 s delay, 4 choices) with pictures of known capuchins monkeys’ faces. All monkeys did discriminate the pictures in both procedures. Performances in probes with partial masks with one fourth of the stimulus hidden were consistent with baseline level. Errors occurred when a picture similar to the correct one was available among the comparison stimuli, when the covered part was the most distinct, or when pictures displayed the same monkey. Capuchin monkeys do match pictures of capuchin monkeys’ faces to the sample. The monkeys treated different pictures of the same monkey as equivalent, suggesting that they respond to the pictures as icons, although this was not true to pictures of other monkeys. Subsequent studies may bring more evidence that capuchin monkeys treat pictures as depictions of real scenes.