Funções de Estímulos Pré-experimentais na Formação de Classes de Equivalência

Three experiments identified factors that did and did not enhance the formation of two-node four-member equivalence classes when training and testing were conducted with trials presented in a trace stimulus pairing two-response (SP2R) format. All trials contained two separately presented stimuli. Half of the trials, called within-class trials, contained stimuli from the same class while the other half, called cross class trials, contained stimuli from different classes. On within class trials, making a YES response was correct and making a NO response was wrong. On cross class trials, making a NO response was correct and making a YES response was wrong. In Experiment 1, similar intermediate percentages of participants (about 50%) formed classes, regardless of whether the responses were labeled YES and NO or SAME and DIFF. Response labeling thus did not influence class formation. Regardless of response labels, failures of class formation were primarily due to failure of class-indicative responding produced by within-class transitivity probes. In Experiment 2, only 50% of participants formed classes without prior training, as in Experiment 1, but 100% of participants formed equivalence classes after the establishment of a generalized transitivity repertoire by use of a programmed transitivity induction protocol. Experiment 3 examined two components of the programmed transitivity induction protocol and found that the exclusion of AC trials had no effect on the percentage of participants who formed equivalence classes, while presenting the stimulus sets in randomized order interfered with equivalence class formation. A further analysis found that a number of stimulus control topographies differentiated between individuals who did and did not form equivalence classes. In general, then, these experiments demonstrate that equivalence classes can be formed reliably when training and testing are conducted in an SP2R format, supporting the view that equivalence class formation can account for the development of conceptual categories in natural settings.

\n O processo de envelhecimento pode gerar perdas cognitivas que, se agravadas, podem acarretar o diagnóstico de demência, sendo a Demência de Alzheimer (DA) a mais comum. A DA é uma doença neurodegenerativas que afeta principalmente a memória e a linguagem. Procedimentos de ensino baseados no paradigma de equivalência de estímulos e no ensino por exclusão, apesar de testados com sucesso em diferentes populações com problemas de desenvolvimento, têm gerado poucas pesquisas com idosos com perdas cognitivas. Esta pesquisa apresenta três estudos, com objetivos distintos, mas complementares. O Estudo 1 teve como objetivo avaliar se idosos institucionalizados sem DA formariam classes de estímulos equivalente a partir de um procedimento de ensino de relações condicionais entre palavras ditadas, fotos, nomes impressos de profissões e de graus de parentesco; adicionalmente, pretendia-se verificar que essas relações se mantinham ao longo de um mês, em três testes de manutenção. Cinco idosos institucionalizados passaram pelo ensino de relações arbitrárias, em uma estrutura de treino linear com ensino de novas relações por exclusão. Testes de equivalência foram conduzidos em seguida à Fase de Ensino, e após cinco, 15 e 30 dias. Todos os idosos demonstraram desempenho por exclusão na Fase de Ensino e aprenderam todas as relações com o número mínimo de blocos de ensino programados (exceto uma participante). Todos os idosos apresentaram formação de classes de equivalência. Quatro dos idosos apresentaram manutenção dessas classes em todos os testes de manutenção. O procedimento, portanto, mostrou-se efetivo para esses idosos e gerou formação de equivalência, apesar da sua condição de institucionalização. O Estudo 2 teve como objetivo avaliar se idosos com DA, também institucionalizados, demonstrariam desempenho por exclusão e aprenderiam relações condicionais entre quatro nomes ditados e quatro fotos, em um procedimento de ensino por exclusão. Seis idosas com diagnóstico de DA passaram por tarefas de emparelhamento ao modelo, em que as relações entre modelos ditados e fotos foram ensinadas por exclusão. Apesar de todas as idosas terem respondido por exclusão na primeira apresentação de um estímulo modelo novo e seu comparação correspondente em pelo menos duas das três tentativas em que tal desempenho era possível, apenas duas mantiveram essa relação ao longo das demais tentativas e aprenderam as relações ensinadas. Possíveis motivos para esse desempenho são discutidos. O Estudo 3 avaliou se idosos institucionalizados, com DA e comprometimento cognitivo, formariam classes de equivalência a partir de um ensino de relações arbitrárias com estrutura de treino um-para-muitos, procedimento de dica atrasada e ensino por exclusão. Quatro idosas passaram pelo ensino de relações condicionais entre estímulos visuais (nomes escritos, fotos e nomes de profissões). Todas aprenderam as relações ensinadas com o número mínimo de blocos programados, porém apresentaram dificuldade em formar classes de equivalência e manter tais relações nos testes de manutenção após cinco e oito dias. Os procedimentos de ensino empregados foram eficientes em gerar a aprendizagem das relações, mas tal aprendizagem, nessas idosas, não sustentou a formação e manutenção de classes de equivalência.\n

Equivalence classes are typically established using match to sample (MTS) procedures with single stimuli serving as samples and comparisons. In a recent study, however, equivalence classes were established with samples and comparisons consisting of compound stimuli (i.e., pairs of abstract symbols). One potential problem using compound stimuli during equivalence class formation, however, is that one element may overshadow the other, thereby disrupting class formation. To address this, the current study used two different compound configurations for incorrect (negative) comparisons during MTS. One group of participants was exposed to negative comparison compounds containing stimuli from only one class (referred to as Type 1 trials) while the other group was exposed to negative comparison compounds containing stimuli from both classes (Type 2 trials) along with Type 1 trials. Class formation was assessed with a test block containing single-element-to-single-element, single-element-to-compound, compound-to-single element, and compound-to-compound derived relations trials. A card sorting test with single elements was also conducted. Results showed that class formation was high and equally likely for both groups; therefore, overshadowing did not occur for either group. Thus, Type 2 trials may be unnecessary during class formation with compound stimuli, and their omission would likely increase efficiency of instruction.

Previous experiments have investigated the function of using pictures or meaningful stimuli on equivalence class formation. For example, when attempting to form three 5-member classes (A→B→C→D→E), findings have shown that pictures used as C stimuli have increased the probability of producing equivalence class formation relative to when all stimuli in the stimulus set are abstract. The present experiment extends the literature by examining whether the formation of equivalence classes varies as a function of having three (C1, C2, and C3), two (C1 and C2), or one (C1) stimulus as a picture in a set of abstract stimuli. Hence, 60 participants were randomly assigned to 4 different experimental groups: 0-picture group or abstract group (ABS), 1-picture group (1PIC), 2-pictures group (2PIC), and 3-pictures group (3PIC). In addition, we had a reference group with abstract shapes only. The findings from the present experiment showed that 2 of 15 participants in the ABS formed classes. Also, two of 15 participants in the 1PIC formed classes, 8 of 15 participants in the 2PIC formed equivalence classes, and 12 of 15 members in the 3PIC formed classes. The statistical analysis supported the notion that equivalence class formation is a function of the number of pictures in a potential equivalence class.

Stimulus meaningfulness has been defined by its hedonic valence, denotative (definitional) and connotative (evaluative) properties, and its influence on forming categories called equivalence classes. Positive or negative hedonic value of a meaningful stimulus transfers to the other members of an equivalence class that contains such a stimulus, and also influences likelihood of class formation. The denotative and connotative properties of meaningful stimuli are instantiated by the responses they produced (simple discriminative functions) and by the selection of other related words (conditional discriminative functions). If a meaningless cue acquires one such stimulus control function, and is included in a set of otherwise meaningless stimuli, its inclusion enhances the formation of an equivalence class. These results suggest ways to enhance equivalence class formation in applied settings. When degree of enhancement matches that produced by the inclusion of a meaningful stimulus in a class, class enhancement can be accounted for by the stimulus control functions it serves, as well as its hedonic, denotative, and connotative properties. We also linked equivalence class formation and meaningfulness to semantic networks, relational frame theory, verbal behavior, and naming.

The present study examined the effects of including stimuli previously trained as members of functional classes or equivalence classes on subsequent equivalence class formation, and isolated the effects of preliminary training from those of the acquired function stimuli. Fifty-six adults were assigned to 1 of 5 conditions. The control group (CONT) received no preliminary training prior to the terminal phase. Participants in the other 4 groups learned two 3-member functional classes and two 3-member equivalence classes during the preliminary phase. The terminal equivalence phase trained two 5-member classes (A → B → C → D → E) comprising abstract forms; the C stimuli in the terminal phase were (a) from the preliminary functional classes for 1 group (ACQ-F), (b) from the preliminary equivalence classes for the second experimental group (ACQ-E), (c) pictures of everyday objects for the picture control group (PIC), and (d) novel, unfamiliar stimuli for the preliminary training control group (PRE-CONT). Class formation yields were 100% in the PIC condition and 11% in the CONT condition; however, low yields in the PRE-CONT, ACQ-F, and ACQ-E conditions were unexpected, suggesting that procedural variables in preliminary training account for more of the subsequent effects on class formation than the stimulus control properties of the acquired function stimuli.

The formation of equivalence classes in individuals with autism spectrum disorder: A review of the literature

The purpose of this study was to evaluate the effects of tact and intraverbal training on the establishment of generalized equivalence classes. Seventeen college students were exposed to tact training, listener testing, and intraverbal training (A'B' and B'C') in two experiments. Visual-visual matching-to-sample and intraverbal tests measured performances consistent with the formation of equivalence classes. Generalization was assessed with four novel sets of stimuli. In the second experiment, matching-to-sample tests for baseline relations (AB, BC) were eliminated to control for the possibility that equivalence classes were developed through exposure to these visual stimulus-stimulus relations. Thirteen of 17 participants passed all matching-to-sample and intraverbal posttests. Results suggest that when trained and emergent intraverbal relations were not maintained or were faulty, participants did not respond correctly during matching-to-sample posttests.

The present study investigated whether simple discrimination procedures produce emergent relations that are consistent with functional and equivalence classes. In Experiment 1, 4 normally capable adults were exposed to simple successive discrimination reversal training. Responses to the S+ (A1, B1, and C1) but not S− (A2, B2, and C2) were reinforced. The participants were then exposed to repeated-reversal training, followed by tests of emergent equivalence relations. In Experiment 2, 4 additional adults were exposed to a simple successive discrimination training procedure using differential responses. Response 1 (R1) was reinforced only when emitted in the presence of A1, B1, or C1 (A1-R1, B1-R1, or C1-R1). Response 2 (R2) was reinforced only in the presence of A2, B2, or C2 (A2-R2, B2-R2, or C2-R2). A new response was then trained in the presence of 1 member of each class (A1-R3, A2-R4). A transfer-of-function test was then conducted to verify whether the new responses would be emitted in the presence of B1, B2, C1, and C2. In both experiments, emergent conditional relations were tested using a go/no-go procedure with compound stimuli. In Experiment 1, all of the participants showed functional classes, and 3 showed patterns that are consistent with the formation of equivalence classes. In Experiment 2, all 4 participants showed patterns that are consistent with functional and equivalence class formation. In these experiments, simple discrimination training generated a range of emergent stimulus relations that mirrored those that are indicative of equivalence class formation.

The purpose of this study was to establish tacts and intraverbals to evaluate whether emergent matching-to-sample (MTS) and intraverbal responding occurred, in accordance with the emergence of intraverbal bidirectional naming (I-BiN) and the formation of equivalence classes. This study replicates and extends the work of Ma et al. (2016) by employing a one-to-many (OTM) training structure, instead of a linear series (LS) training structure. In addition, the study included sorting post-tests and a social validity survey. Eight adult participants underwent MTS pre-tests, followed by tact training of experimental stimuli and testing for emergent listener responses. Then, intraverbal training (A’B’/A’C’) was introduced before conducting MTS post-tests and I-BiN post-tests, as well as sorting post-tests. A post-experimental interview and a social validity survey completed the study. The main finding indicated that training of baseline intraverbal relations using an OTM training structure likely facilitated the establishment of new conditional ties in accordance with the emergence of I-BiN towards the experimental stimuli and the formation of equivalence classes. All participants reported using verbal mediation strategies, such as tacts and intraverbals established during training and testing, as well as self-generated tacts and intraverbals.

Equivalence class formation by college students was influenced through the prior acquisition of conditional discriminative functions by one of the abstract stimuli (C) in the to-be-formed classes. Participants in the GR-0, GR-1, and GR-5 groups attempted to form classes under the simultaneous protocol, after mastering 0, 1, or 5 conditional relations between C and other abstract stimuli (V, W, X, Y, Z) that were not included in the to-be-formed classes (ABCDE). Participants in the GR-many group attempted to form classes that contained four abstract stimuli and one meaningful picture as the C stimulus. In the GR-0, GR-1, GR-5, and GR-many groups, classes were formed by 17, 25, 58, and 67% of participants, respectively. Thus, likelihood of class formation was enhanced by the prior formation of five C-based conditional relations (the GR-5 vs. GR-0 condition), or the inclusion of a meaningful stimulus as a class member (the GR-many vs. GR-0 condition). The GR-5 and GR-many conditions produced very similar yields, indicating that class formation was enhanced to a similar degree by including a meaningful stimulus or an abstract stimulus that had become a member of five conditional relations prior to equivalence class formation. Finally, the low and high yields produced by the GR-1 and GR-5 conditions showed that the class enhancement effect of the GR-5 condition was due to the number of conditional relations established during preliminary training and not to the sheer amount of reinforcement provided while learning these conditional relations. Class enhancement produced by meaningful stimuli, then, can be attributed to their acquired conditional discriminative functions as well as their discriminative, connotative, and denotative properties.

This paper reports two experiments that investigated the role of verbal behavior in the emergence and generalization of contextually controlled equivalence classes. During both experiments, participants were trained with two different combinations of the same easily nameable, yet formally unrelated, pictorial stimuli. Match-to-sample baselines for eight four-member classes were established under the contextual control of two colors. In the presence of one color, conditional relations were established between stimuli whose normative names rhymed. In the presence of the other color, conditional relations were established between stimuli whose normative names did not rhyme. Although, during Experiment 1, all participants demonstrated equivalence classes involving rhyming stimuli, none demonstrated the formation of nonrhyme equivalence classes. To investigate this finding, Experiment 2 evaluated whether participants would demonstrate both rhyme and nonrhyme equivalence classes given more extensive exposure to the experimental contingencies. All participants demonstrated contextually controlled rhyme and nonrhyme equivalence classes, although rhyme classes were demonstrated with greater facility than nonrhyme classes. Results indicate that visual stimuli are named, that verbal bases for stimulus classification can affect the emergence of contextually controlled equivalence classes, and that untrained contextually controlled conditional discriminations involving novel stimuli can emerge on the basis of participants' verbal behavior.

The current study investigated the effect of stimulus meaningfulness on the formation of equivalence classes in a conditional discrimination training task. Nonsense syllables rated as high or low in meaningfulness (m) on the Glaze (1928) and Krueger (1934) rating scales were presented in a matching-to-sample task. Thirteen participants were trained to produce B1 and C1 given the sample A1, B2 and C2 given A2, and B3 and C3 given A3. Participants’ performances during training and the emergence of a derived set of responses during testing (B1-C1, B2-C2, B3-C3) were analyzed as a function of m of stimuli within the relations. Training performances were predicted by m of the stimuli, with less error overall associated with low m configurations, and less error where sample and comparison items matched in terms of m (both high or both low).

Seven participants received conditional discrimination training that established the 12 conditional relations A1B1, A2B2, A3B3, A1C1, A2C2, A3C3, D1E1, D2E2, D3E3, D1F1, D2F2, and D3F3. The A stimuli were pictures of faces portraying emotional expressions; the others were arbitrary forms. Correct responses resulted in presentations of class-specific reinforcers, Sr1, Sr2, and Sr3. After training, tests confirmed the formation of ABC and DEF equivalence classes. Further tests then documented the merger of the classes and the emergence of SrB, SrC, SrE, and SrF relations, showing that the class-specific reinforcers were equivalence class members. Finally, participants did Semantic Differential ratings that tested whether the emotional valence of the A stimuli transferred to the arbitrary forms, B and E. The results show that participants' evaluations of the B and E stimuli were similar to evaluations of the A stimuli made by participants of a control group. This finding is considered as a demonstration that class-specific outcomes can mediate class merger phenomena and the transfer of functions through members of merged classes.

AB, BC, CD, and DE were established by conditional discrimination training. Symmetry, transitivity, and equivalence tests were then passed demonstrating the formation of 5-member equivalence classes. These tests were passed even though they were conducted in the absence of baseline relations. A new stimulus (F) was then linked to a class member (A) by stimulus fading conducted in the context of simple discrimination training. Thereafter, subjects passed FB, FC, FD, FE, BF, CF, DF, and EF tests, demonstrating that F functioned as a new member of the A-E class. The expansion of equivalence classes can also be accomplished by the use of simple discrimination training combined with stimulus fading, in addition to the typical use of conditional discrimination training. Equivalence classes, then, can be defined independently of conditional discrimination procedures.