Effects of a meaningful, a discriminative, and a meaningless stimulus on equivalence class formation

Abstract

Thirty college students attempted to form three 3-node 5-member equivalence classes under the simultaneous protocol. After concurrent training of AB, BC, CD, and DE relations, all probes used to assess the emergence of symmetrical, transitive, and equivalence relations were presented for two test blocks. When the A-E stimuli were all abstract shapes, none of 10 participants formed classes. When the A, B, D, and E stimuli were abstract shapes and the C stimuli were meaningful pictures, 8 of 10 participants formed classes. This high yield may reflect the expansion of existing classes that consist of the associates of the meaningful stimuli, rather than the formation of the ABCDE classes, per se. When the A-E stimuli were abstract shapes and the C stimuli became S(D)s prior to class formation, 5 out of 10 participants formed classes. Thus, the discriminative functions served by the meaningful stimuli can account for some of the enhancement of class formation produced by the inclusion of a meaningful stimulus as a class member. A sorting task, which provided a secondary measure of class formation, indicated the formation of all three classes when the emergent relations probes indicated the same outcome. In contrast, the sorting test indicated "partial" class formation when the emergent relations test indicated no class formation. Finally, the effects of nodal distance on the relatedness of stimuli in the equivalence classes were not influenced by the functions served by the C stimuli in the equivalence classes.

Keywords: Stimulus Equivalence; acquired discriminative function; college students; comparison selection in matching to sample trials; enhanced equivalence class formation; meaningfulness; nodal distance effects.

Fig 1

The stimuli used as members of the equivalence classes were abstract and familiar picture-stimuli as shown in the two top sections. The bottom section shows the stimuli used during discrimination training. (See text for more details).

Fig 2

The effect of the function served by the C stimulus on the percentage of participants who formed equivalence classes, in the Meaningful C Stimulus (PIC), Acquired Discriminative Function (ACQ) and Abstract Stimulus (ABS) conditions.

Fig 3

The median number of trials needed to acquire the baseline relations in each condition, for two subgroups of participants: those who did and did not subsequently form equivalence classes.

Fig 4

The average percentage of trials that evoked class indicative comparison selections for the last block of feedback reduction during training (BL–T), and the baseline (BL), symmetrical (SYM), and 1-, 2- and 3-node probes (1N, 2N, 3N) for participants who showed the delayed emergence of the classes in the PIC and ACQ groups. For each group separate functions are plotted for test blocks 1 and 2.

Fig 5

Median reaction times of correct and incorrect responses plotted as functions of the type of relation (x-axis). Data within each panel are separated by the terminal baseline training trials and the first and second test blocks. The two panels separate reaction times of participants who did and did not form equivalence classes. Data are aggregated across groups.