This article provides a comprehensive overview of the development of a behavior-analytic alternative to the popular implicit association test (IAT), namely, the function acquisition speed test (FAST). The IAT appears, prima facia, to indirectly assess participants’ learning histories with regard to the categorization of stimuli. However, its origin within cognitive psychology has rendered it replete with mentalism, conceptual ambiguity, statistical arbitrariness, and confounding procedural artifacts. The most popular behavioral alternative to the IAT, the widely used implicit relational assessment procedure (IRAP), has inherited many of these concerning artifacts. In this article, we present a behavior-analytic critique of both the IAT and IRAP, and argue that a behavior-analytic approach to implicit measures must have stimulus control front and center in its analysis. We then outline a series of early research studies that provided the basis for a potentially superior procedure within our field. We go on to outline how this early research was harnessed in stepwise research, guided by a strict adherence to traditional behavior-analytic methods for the analysis of stimulus relations, to increasingly modify a test format fit for the behavior analyst interested in assessing stimulus relatedness.