Japanese listeners' perception of phonemic vowel length distinction in Sinhala

Sinhala, an underrepresented Indo-Aryan language, and Japanese share phonological system similarities, such as phonemic vowel length distinctions and heavily overlapping vowel inventories. While the long-to-short vowel duration ratio for Japanese is about 2.2–2.3 depending on the vowel [Yazawa & Kondo, 2019, ICPhS], the ratio for Sinhala has never been calculated, to our knowledge. We recorded 12 Sinhala speakers saying 48 randomized words in a carrier sentence (6 vowel types × 4 long-short minimal pairs), for a total of 576 samples to determine duration ratios. Results showed the Sinhala long vowels were approximately 2.4– 2.8 times longer than short vowels, an even larger difference than Japanese. We hypothesized that naive Japanese listeners would perceive Sinhala vowel-length differences with a high degree of accuracy, but that they would have trouble with the vowel /æ/ that is not in their inventory. Perceptual tests were conducted with 22 naive Japanese listeners and 9 native Sinhala controls, who completed 96 reaction-time trials each, totaling 2976 responses. Japanese listeners demonstrated higher mean accuracy (94% vs. 93%) in distinguishing Sinhala vowel lengths, but Sinhala listeners were significantly faster. Both groups had higher reaction times in identifying the vowel /æ/.