Certain ill-formed phonological structures are systematically under-represented across languages and misidentified by human listeners. It is currently unclear whether this results from grammatical phonological knowledge that actively recodes ill-formed structures, or from difficulty with their phonetic encoding. To examine this question, we gauge the effect of two types of tasks on the identification of onset clusters that are unattested in an individual's language. One type calls attention to global phonological structure by eliciting a syllable count (e.g., does "medif" include one syllable or two?). A second set of tasks promotes attention to local phonetic detail by requiring the detection of specific segments (e.g., does "medif" include an "e"?). Results from five experiments show that, when participants attend to global phonological structure, ill-formed onsets are misidentified (e.g., "mdif"[right arrow]"medif") relative to better-formed ones (e.g., "mlif"). In contrast, when people attend to local phonetic detail, they identify ill-formed onsets as well as better-formed ones, and they are highly sensitive to non-distinctive phonetic cues. These findings suggest that misidentifications reflect active recoding based on broad phonological knowledge, rather than passive failures to extract acoustic surface forms. Although the perceptual interface could shape such knowledge, the relationship between language and misidentification is a two-way street. (Contains 8 figures, 1 table and 2 notes.)