Enhancement of the vowel quantity contrast in Japanese and German by F0 and vowel quality

Previous studies on the perception of vowel quantity in Japanese and German have shown an influence of F0 for Japanese and of vowel quality for German. The current study investigates F0 and vowel quality enhancement of vowel length perception in both languages. Native speakers of Japanese and German were presented with three series of stimuli: (i) vowel continua for the vowels /a/, /e/, and /i/ which differed in duration only; (ii) vowel continua for the same vowels which differed in duration and the steepness of the F0 fall over the vowel; and (iii) vowel continua for the same vowels containing both durational and quality cues. While vowel quantity in the first two series was perceived categorically by Japanese listeners, vowel quantity in the stimuli testing the influence of vowel quality was perceived as gradual rather than categorical by the same listeners. German listeners perceived all series as categorical. Thus F0 cues generally enhance the distinction of the vowel length contrast whereas the presence of quality cues facilitates the distinction in German but impedes the perception of the same distinction in Japanese. This suggests that enhancement of vowel quantity is governed by perceptual cues that are in part language specific.