Native dialect matters: perceptual assimilation of Dutch vowels by Czech listeners.

Naive listeners' perceptual assimilations of non-native vowels to first-language (L1) categories can predict difficulties in the acquisition of second-language vowel systems. This study demonstrates that listeners having two slightly different dialects as their L1s can differ in the perception of foreign vowels. Specifically, the study shows that Bohemian Czech and Moravian Czech listeners assimilate Dutch high front vowels differently to L1 categories. Consequently, the listeners are predicted to follow different paths in acquiring these Dutch vowels. These findings underscore the importance of carefully considering the specific dialect background of participants in foreign- and second-language speech perception studies.