Recent research using the event-related potential (ERP) technique has shown that equivalence relations have properties similar to genuine semantic relations. This study aimed to advance electrophysiological investigations of the functional overlap between semantic and equivalence relations. The N400 component, an index of semantic processing, was used to measure whether semantic relations were experimentally established between arbitrary stimuli. The stimuli became equivalent via a matching-to-sample training designed to maximize the establishment of equivalence relations and the strength of the classes. Non-equivalent pairs of stimuli elicited larger N400 responses than equivalent pairs in electrodes placed over the central and parietal scalp regions, providing additional support for the assumption that stimulus equivalence is an appropriate model of semantic relations. Latency of the N400 component was shorter than in previous studies, probably due to experimental parameters that maximized relational strength. These data raise the possibility that N400 latency may provide a continuous measure of relational strength, thus supplementing the all-or-none character of equivalence tests based on matching to sample.

Este estudo investigou evidências de validade e precisão de um instrumento de diferencial semântico que tem sido utilizado para medir a transferência de significados entre estímulos equivalentes. Um total de 196 estudantes universitários avaliou fotografias de faces expressando emoções e também figuras abstratas, utilizando um instrumento composto por 13 escalas bipolares ancoradas por adjetivos opostos. A análise fatorial dos dados coletados forneceu indicações da validade do instrumento e os coeficientes alfa obtidos indicam que os dois fatores extraídos nesta análise possuem níveis de precisão aceitáveis, embora um dos fatores deva ser revisto. Discute-se que o modelo de equivalência de estímulos, entendido como um modelo experimental de relações simbólicas, pode se beneficiar de instrumentos capazes de fornecer medidas válidas de transferência de significado.

This study assessed evidence of validity and precision of a semantic differential test that has been used to measure the transfer of meaning among equivalent stimuli. Participants were 196 college students who evaluated pictures of faces expressing emotions and also abstract pictures using an instrument comprised by 13 bipolar scales anchored by opposite adjectives. The factor analysis of the data evidenced the validity of the instrument. Values of alpha coefficients indicated that the factors extracted by this analysis have acceptable levels of precision, although one of the factors might be revised. It is discussed that the stimulus equivalence paradigm, an experimental model for symbolic relations, can benefit from instruments that provide valid measures of meaning transfer.

The present study investigated whether overtraining of the conditional discriminations that are the prerequisites of equivalence class formation strengthens the relations among stimuli in an equivalence class. Two groups of college students formed equivalence classes that consisted of faces that expressed emotions (A) and arbitrary stimuli (B, C, D, and E). The overtraining group had twice as many training trials as the regular training group. For participants who formed equivalence classes, relational strength was evaluated by the generalization of expressed emotions from the A to the D stimuli, which was measured using a semantic differential. An untrained control group showed semantic differential scores that were positive for happy faces, negative for angry faces, and neutral for the D stimuli. For the experimental groups, the D stimuli, when included in equivalence classes, produced scores that were similar to those produced by the equivalent faces. The overtraining group, however, had average values closer to the values of the faces than the regular training group. These results indicate that the amount of training is an experimental parameter that influences the strength of relations between stimuli that are found to be equivalent in matching-to-sample tests.

Relações semânticas entre estímulos equivalentes foram avaliadas utilizando "tentativas de decisão léxica" e diferencial semântico. Foram utilizadas as estruturas de treino conhecidas como "um-para-muitos" e "muitos-para-um" na geração de três classes de estímulos equivalentes envolvendo cinco conjuntos de estímulos: A, B, C, D e E. Para um grupo de participantes, denominado de Grupo Um para Muitos (GUM), as relações diretamente treinadas obedeciam à estrutura AB, BC, CD e CE; um outro grupo experimental, denominado de Grupo Muitos para Um (GMU), foi treinado na estrutura DC, EC, CB e BA. Para os dois grupos, os estímulos do conjunto B eram fotografias de faces expressando emoções e os estímulos dos conjuntos A, C, D e E eram figuras abstratas. A seguir, duas figuras (já vistas ou novas) eram apresentadas em seqüência, como "dica" e "alvo", em tentativas em que o participante respondia se reconhecia ou não a figura alvo. As respostas foram mais rápidas quando dica e alvo pertenciam à mesma classe, reproduzindo com estímulos abstratos equivalentes o efeito de dica semântica. Figuras abstratas foram então avaliadas por diferencial semântico. As avaliações do GUM foram similares às avaliações das faces por um grupo controle e as avaliações do GMU não foram. Os dados sugerem que a intensidade relativa da transferência de significados entre estímulos equivalentes pode depender da direção das relações que os participantes devem estabelecer.

Semantic relations among equivalent stimuli were evaluated by lexical decision tasks and a semantic differential. Two training structures, known as "one-to-many" and "many-to-one", were employed in order to generate three classes of equivalent stimuli involving five sets of stimuli: A, B, C, D and E. Stimuli for set B were pictures of faces expressing emotions whereas stimuli for sets A, C, D and E were abstract pictures. For one group of participants, the One-to-many Group, the directly trained relations were AB, BC, CD and CE; for the other experimental group, the Many-to-one Group, the directly trained relations were DC, EC, CB and BA. Two pictures were then presented in sequence as "prime" and "target" in trials in which participants responded whether they recognized or not the target. Responses were faster when prime and target belonged to the same equivalent class, reproducing the semantic priming effect. Abstract pictures were then evaluated through the semantic differential. Evaluations by the One-to-many Group were similar to the evaluations of the faces made by a control group, but those made by the Many-to-one Group were not. The data suggest that the transfer of meaning among equivalent stimuli may depend on the relations which are established by the participants.

Este estudo apresenta um procedimento para verificar a existência de "graus de relacionamento" diferentes entre estímulos equivalentes por meio de uma medida quantitativa de compartilhamento de funções. Dois grupos de estudantes universitários participaram do estudo. Os participantes do grupo experimental estabeleceram classes de equivalência entre figuras abstratas e fotografias de faces expressando alegria, raiva e nojo. Em seguida, avaliaram algumas das figuras abstratas usando um instrumento de diferencial semântico. O mesmo instrumento foi utilizado na avaliação das faces e figuras pelos participantes do grupo controle, não treinados a estabelecer relações entre esses estímulos. Esses últimos participantes avaliaram as figuras como neutras e as avaliações que fizeram das faces corresponderam às avaliações das figuras equivalentes a elas feitas pelos participantes do grupo experimental. A comparação entre os valores atribuídos às faces e às figuras dá uma medida quantitativa do grau de relacionamento entre esses estímulos e essa medida pode ser usada no estudo de parâmetros da formação de classes como o número de nódulos.

There are methodological difficulties to quantify the relatedness of equivalent stimuli. The purpose of this study was to create an instrument that could be helpful in this process. Two groups of college students took part in this study. The experimental group established equivalence classes comprised of abstract pictures and pictures of faces expressing anger, happiness and disgust. They then evaluated some of these pictures with a semantic differential. The control group used the same instrument in evaluating faces and figures, untrained in establishing relations between those stimuli. The control group assessed the figures as neutral and their assessment of the faces corresponded to that carried out by the participants of the experimental group - to them, the figures were equivalents to the faces. The comparison between the values attributed to the faces and figures provides a quantitative measurement of the degree of relatedness between those stimuli and that may be used to study parameters such as the number of nodes.