A criterial interlocutor tally for successful talker adaptation?

Part of the remarkable efficiency of listening is accommodation to unfamiliar talkers’ specific pronunciations by retuning of phonemic intercategory boundaries. Such retuning occurs in second (L2) as well as first language (L1); however, recent research with emigrés revealed successful adaptation in the environmental L2 but, unprecedentedly, not in L1 despite continuing L1 use. A possible explanation involving relative exposure to novel talkers is here tested in heritage language users with Mandarin as family L1 and English as environmental language. In English, exposure to an ambiguous sound in disambiguating word contexts prompted the expected adjustment of phonemic boundaries in subsequent categorisation. However, no adjustment occurred in Mandarin, again despite regular use. Participants reported highly asymmetric interlocutor counts in the two languages. We conclude that successful retuning ability requires regular exposure to novel talkers in the language in question, a criterion not met for the emigrés’ or for these heritage users’ L1