Operant theory, with its reliance on functionally-defined response classes, has little difficulty with the transposition literature. Selecting the larger, or brighter, or rounder stimulus simply becomes a learned operant. Organisms learn to discriminate the relevant stimulus relation, as well as the formal dimension along which the relation is relevant, through multiple training trials in which the relata vary. If selecting only the larger of two stimulus objects is reinforced over a series of trials with varying objects, there is no reason to be surprised if an organism begins to respond to the relation between the stimuli rather than their absolute characteristics. The consequences have shaped just such a response class.

To avoid confusion, the Latin term relata will be used throughout the book to describe related events since the English term, relates, is obscure and has a much more dominant meaning as a verb. In some of our previous writings we have incorrectly used the term relatae, in the mistaken belief that the Latin word was feminine.