Experimental work on free will typically relies on deterministic stimuli to elicit judgments of free will. We call this the Vignette-Judgment model. We outline a problem with research based on this model. It seems that people either fail to respond to the deterministic aspects of vignettes when making judgments or that their understanding of determinism differs from researcher expectations. We provide some empirical evidence for this claim. In the end, we argue that people seem to lack facility with the concept (...) of determinism, which calls into question the validity of experimental work operating under the Vignette-Judgment model. We also argue that alternative experimental paradigms are unlikely to elicit judgments that are philosophically relevant to questions about the metaphysics of free will. (shrink)