Cross-language differences in speech perception have traditionally been linked to phonological categories, but it has become increasingly clear that language experience has effects beginning at early stages of perception, which blurs the accepted distinctions between general and speech-specific processing. The present experiments explored this distinction by playing stimuli to English and Japanese speakers that manipulated the acoustic form of English /r/ and /l/, in order to determine how acoustically natural and phonologically identifiable a stimulus must be for cross-language discrimination differences to emerge. Discrimination differences were found for stimuli that did not sound subjectively like speech or /r/ and /l/, but overall they were strongly linked to phonological categorization. The results thus support the view that phonological categories are an important source of cross-language differences, but also show that these differences can extend to stimuli that do not clearly sound like speech
