What makes some metaphors easier to understand than oth-ers? Theoretical accounts of metaphor processing appeal todimensions like conventionality and aptness to explain vari-ability in metaphor comprehensibility. In a typical experiment,one group of naive participants rates a set of metaphoric sen-tences along these dimensions, while another is timed readingthe same sentences. Then, the ratings are used to predict re-sponse times in order to identify the most relevant linguistic di-mension for metaphor comprehension. However, surprisinglyhigh correlations between ratings of theoretically orthogonalconstructs and the results of an experiment in which a con-text manipulation affected ratings of metaphor conventionalityand aptness suggest that these measures should be treated asdependent, rather than explanatory, variables. We discuss theimplications of this perspective for theories of language pro-cessing.