This is the same study that was presented at the Developmental Linguistics Research Group on 3 October.
Phonological representations of L2 words may not be completely distinct in the mental lexicon when they involve contrasts lacking in the L1. In order to isolate the effects of such representational indeterminacy from those of speech perception, we designed two experiments building on the finding that homophones can induce identification errors and slower processing in silent reading. Native speakers of English, Japanese, Spanish, and Arabic carried out a visual semantic categorization task and a semantic-relatedness decision task in English. The results show that, when controlled for writing systems, L2 speakers are more likely to commit false positives and show slower reaction times with homophones and also minimal pairs that involve a non-L1 contrast than with spelling-matched control words. Since the effects are not direct consequences of auditory misperception, they provide independent evidence that phonemic mismatches between the L1 and L2 can lead to non-distinct mental lexical representations of L2 words.