Learning-set de reversões, de discriminações simples em macaco-prego / Learning-set of simple discrimination reversals in a capuchin monkey

A aquisição repetida de discriminações simples pode determinar uma crescente eficiência na aprendizagem dessas discriminações. Esse efeito é conhecido como learning-set. O mesmo efeito pode ser observado em reversões repetidas de uma mesma discriminação ou em reversões repetidas de discriminações simples combinadas (RRDSC). O presente estudo relata a aplicação de RRDSC com até seis estímulos (três positivos e três negativos), simultaneamente, com um macaco-prego (Cebus cf. apella). Ao longo das repetidas reversões, avaliou-se o efeito de learning-set em duas variáveis: a) número de acertos processados até o critério de seis acertos consecutivos e b) número de tentativas até o critério. Os dados indicam a obtenção de learning-set nas RRDSC. Discutem-se os procedimentos que mais contribuíram para essa demonstração

Repeated acquisition of simple discrimination may determine an increasing efficiency in learning suchdiscriminations. This effect is known as learning-set. The same effect can be observed on repeatedreversals of the same discrimination or on repeated yoked reversals of simple discriminations(RYRSD). The present study reports the use of RYRSD with up to six stimuli (three positive and threenegative) simultaneously with a capuchin monkey (Cebus cf apella). Over the course of the repeatedreversals, the learning-set effect was evaluated taking into account two variables: a) number of correctresponses processed until criterion of six consecutive correct responses is reached and b) number oftrials until the criterion is reached. The data indicate learning-set in simple discrimination on yokedreversals. We discuss the procedures that contributed the most to this demonstration

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. We present, in this study, 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.

Cebus cf. apella exhibits rapid acquisition of complex stimulus relations and emergent performance by exclusion

A "second generation" matching-to-sample procedure that minimizes past sources of artifacts involves (1) successive discrimination between sample stimuli, (2) stimulus displays ranging from four to 16 comparisons, (3) variable stimulus locations to avoid unwanted stimulus-location control, and (4) high accuracy levels (e.g., 90 percent correct on a 16-choice task in which chance accuracy is 6 percent). Examples of behavioral engineering with experienced capuchin monkeys included four-choice matching problems with video images of monkeys with substantially above-chance matching in a single session and 90 percent matching within six sessions. Exclusion performance was demonstrated by interspersing non-identical sample-comparison pairs within a baseline of a nine-comparison identity-matching-to-sample procedure with pictures as stimuli. The test for exclusion presented the newly "mapped" stimulus in a situation in which exclusion was not possible. Degradation of matching between physically non-identical forms occurred while baseline identity accuracy was sustained at high levels, thus confirming that Cebus cf. apella is capable of exclusion. Additionally, exclusion performance when baseline matching relations involved non-identical stimuli was shown