For decades, experiential measures (i.e., self- and informant-report) have dominated clinical psychological science as the primary methods of investigating the nature, causes, and consequences of psychopathology. Recent efforts to understand psychopathology in a comprehensive manner, bridging across measurement modalities and study designs, have yielded disappointing results and small cross-domain effect sizes. This problem has stymied progress in diagnosing and treating mental illness. We contend that we continue to struggle to link different units of analysis in psychopathology research because, as a field, we have not learned the lessons that have been detailed in the literature since at least the 1950s. We argue that our reliance on single units of analysis (e.g., only self-report or only neuroimaging) to conceptualize and operationalize psychological constructs lies at the heart of our struggles. Conflation of a construct with its operationalization in a single measurement modality fundamentally limits the ability to understand its manifestation in other units of analysis. To make progress toward a fine-grained understanding of the symptoms, signs, and mechanisms of psychopathology, we must move past the siloed reification of constructs and prioritize new, integrated research paradigms. (PsycInfo Database Record (c) 2023 APA, all rights reserved).