This article examines an important and thorny problem in interview research: How to assess whether what people say motivated their actions actually did so? We ask three questions: What specific challenges are at play? How have researchers addressed them? And how should those strategies be evaluated? We argue that such research faces at least five challenges--"deception, recall error, reasonableness bias, intentionality bias," and "single-motive bias"--that more than a dozen strategies have been deployed to address them; that the strategies have been "external, internal," or "interactional" in nature; and that each class of strategies demands distinct evaluation criteria. Researchers will likely fail to uncover motivation if they ignore the possibility of each challenge, conflate one challenge with another, or deploy strategies unmatched to the challenge at hand. Our work helps systematize the evaluation of interview-based studies of motivated action and strengthen the scientific foundations of in-depth interview research.