Contextual Control of New Equivalence Classes

This study describes a method which allows for the unambiguous measurement of contextual control of equivalence class membership. Two equivalence classes, Ai-Bi-Ci and Aj-Bj-Cj, were formed by training Ai-Bi, Bi-Ci, Aj-Bj, and Bj-Cj in the presence of a short line denoted by X. In a subsequent test, all relations were displayed in the presence of a long line denoted by Y, to see if performances would indicate the emergence of the alternative classes Ai-Bj-Cj and Aj-Bi-Ci. If they did not emerge, Ai-Bj, Bj-Cj, Aj-Bi, and Bi-Ci were trained in the presence of Y, and the emergent relations test performances indicated the development of the alternative classes. This three-stage cycle was repeated with new sets of stimuli until the alternative classes emerged during the initial tests conducted in the presence of Y for two consecutive sets of new stimuli. This occurred after training with 4, 6, and 12 new classes for three of the five subjects. These outcomes could not be accounted for in terms of compound or multielement stimulus control because the contextual stimuli influenced membership in new equivalence classes. These results, then, provided an unequivocal demonstration of contextual control over the membership of stimuli in new equivalence classes. Finally, performances occasioned by primary generalization tests showed that contextual control extended to many lines that were similar in length to those used as the X and Y stimuli. These contingency-based performances have the formal appearance of rule-governed behavior.