Meaningful Stimuli and the Enhancement of Equivalence Class Formation

Abstract

After the direct training of baseline conditional relations, the emergence of derived relations that have the properties of reflexivity, symmetry and transitivity documents the formation of equivalence classes. Studies on the formation of these equivalence classes have shown that the probability of class formation is influenced by a wide array of variables. The meaningfulness of the stimuli used has been found to be one of such important variables. The formation of equivalence classes that include meaningless or abstract stimuli only has been found to be less probable. However, the inclusion of a meaningful stimulus, such as a familiar picture in a set of other meaningless stimuli can help to convert that set of stimuli into an equivalence class. In five studies with college students, this thesis has explored the properties of meaningful stimuli that account for the class enhancement they produce. Study 1 explored how a simple discriminative function acquired by an abstract stimulus through simultaneous and/or successive discrimination training enhanced the formation of an equivalence class of which that stimulus was a member. In two experiments, Study 2 investigated how the order of training, familiar pictures, and abstract stimuli that acquired discriminative functions influenced equivalence class formation. In yet another two experiments, Study 3 studied the effect of the use of a meaningful stimulus as a class member on equivalence class formation. Two parallel groups were trained to form three 3-node 5-member equivalence classes (A B C D E) under the simultaneous protocol in both experiments. The baseline relations AB, BC, CD, and DE were trained in a serialized manner in Experiment 1 while Experiment 2 involved the concurrent training of baseline relations. Study 4 investigated whether the acquisition of an identity conditional discriminative function by a meaningless stimulus using simultaneous or delayed matching procedures would influence the likelihood of formation of an equivalence class of which it is a member along with other meaningless stimuli. In a replication to Study 4, Study 5 investigated how equivalence class formation was enhanced by the inclusion of one abstract stimulus that had acquired an identity or arbitrary conditional discriminative function on a simultaneous or delayed basis, prior to the establishment of the classes. In addition to their traditional connotative and denotative properties, these studies extend our knowledge on the class enhancing properties of meaningful stimuli to include acquired discriminative functions and delayed relational (identity and arbitrary) functions. The studies also strengthen existing findings that the inclusion of a meaningful stimulus in a set of other meaningless class enhances the formation of equivalence classes. However, its inclusion alone is shown to be insufficient to generate the class enhancement and that, the order of introduction in the serial training of the baseline relations for a class, the structural location of the meaningful stimulus in the training structure as well as its behavioral functions interact with the meaningful stimulus to account for their class enhancement. Finally, there was a strong concordance between two trial formats: matching to sample trials during class formation and sorting during post class formation sorting test in terms of participants’ performances indicative of equivalence class formation.