Bilingual advantage? Perception of the Japanese consonant length contrast by Monolingual vs bilingual speakers of Mongolian

Japanese is a quantity language that uses durational variation contrastively for both vowels and consonants. It is widely acknowledged that length contrast is difficult for non-native speakers from diverse first language (L1) backgrounds. The extent to which these difficult Japanese sounds are processed accurately by native and non-native listeners was examined via the AXB discrimination task. Our target groups consisted of native speakers of Mongolian who had no experience with Japanese and lived either in Hohhot, China or Ulaanbaatar, Mongolia. The former spoke both Mandarin and Mongolian in their daily life (bilingual), but not the latter (monolingual). Their perception accuracy was compared to that of native speakers of Japanese and Mandarin.The control Japanese group was more accurate than all non-native groups. Among the non-native groups, there was no significant difference between the monolingual and bilingual Mongolian groups, but only the bilingual Mongolian group was more accurate than the Mandarin group. This suggests that bilingualism may give listeners some indirect advantage in that the bilingual Mongolian group resembled the native control group to a greater extent than did the monolingual Mongolian group.