F0 range instead of F0 slope is the primary cue for the falling tone of Mandarin

It has been well known that rising/falling pitch is employed to distinguish the rising (R) or falling (F) tones from the high-level (H) tone in Mandarin, but whether F0 range or F0 slope is the more critical F0 cue to perception is still inconclusive. To clarify this issue quantitatively, we took the F tone as the test case, and conducted two-alternative forced choice identification tests on two types of two-dimensional high-level-falling (H-F) tonal continua, one of which was manipulated along F0 range and duration ("F0 range continuum") while the other along F0 slope and duration ("F0 slope continuum"). Experimental results indicated that F0 range was the primary cue because it resulted in a more robust (less duration-dependent) perceptual boundary than F0 slope. Meanwhile, the perceptual boundary in F0 range was not fully independent of but mildly modulated by duration, suggesting that duration (or equivalently, F0 slope) played a supplementary role in identifying the H-F tonal contrast.