Visual identification of Taiwan Mandarin rounded vowels

While auditory and visual cues jointly support vowel perception, the role of visual information alone in vowel identification remains understudied. This study examines how Taiwan Mandarin speakers identify rounded vowels using visual-only input. Results reveal an asymmetric pattern between /y/ and /u/, with a bias toward /u/ as the default rounded vowel and greater difficulty identifying /y/. Signal detection analyses further indicate a higher response criterion for /y/. This default preference for /u/ appears to reflect phonological distributions in the language or a universal preference for the more peripheral vowel. Varying degrees of visual input did not modulate identification strategies, and visual information provided only limited support for distinguishing between /u/ and /y/.