List of words with common phonemes (e.g. *mat, man, ran, rat, pat, pan*) are more difficult to recall in order than lists of words with distinct phonemes (e.g. *clock, spoon, hand, bus, door, fish*). This *phonological similarity effect* is often attributed to confusion of features within the phonological store. However, in standard examinations of the phonological similarity effect, the acoustic and phonological properties of the stimuli are not independent. In the current project, participants were trained to map ambiguous, vocoded stimuli to either the original phonologically similar word forms or plausible, but more distinct word forms. In this way, the original goal of this project was to tease apart and independently assess the acoustic and phonological properties of the stimuli (see preregistration tab). However, an unexpected but clear finding emerged. Neither acoustic nor phonological similarity consistently predicted the poorest performance. Instead, participants' performance was most severely impaired when they were required to map strings of words to the mismatched labels -- despite their ability to make these mappings when words were in isolation. These results are interpreted in terms of increased difficulty when mapping in adverse listening conditions. **Published Communication.** https://dx.doi.org/10.1080/25742442.2020.1846012 **Data Citation.** See citation list in the top-right corner of the main project page. This OSF project contains the data and analysis script the experiment in our paper. If you would like to use the data in future published work, please cite both the paper and this OSF project. **Ethics Approval.** This project was approved by the Institutional Review Board at Boys Town National Research Hospital under IRB #17-14-XP (PI: Angela AuBuchon). **Contact.** For any further questions or comments, please email Dr. Adam Bosen at adam.bosen@boystown.org