Voice onset time is necessary but not always sufficient to describe acquisition of voiced stops: The cases of Greek and Japanese.

The age at which children master adult-like voiced stops can generally be predicted by voice onset time (VOT): stops with optional short lag are early, those with obligatory lead are late. However, Japanese voiced stops are late despite having a short lag variant, whereas Greek voiced stops are early despite having consistent voicing lead. This cross-sectional study examines the acoustics of word-initial stops produced by English-, Japanese-, and Greek-speaking children aged 2 to 5, to investigate how these seemingly exceptional mastery patterns relate to use of other phonetic correlates. Productions were analyzed for VOT, f0 and spectral tilt (H1-H2) in Japanese and English, and for amplitude trajectory in Greek and Japanese. Japanese voiceless stops have intermediate lag VOT values, so other "secondary" cues are needed to differentiate them from the voiced short lag VOT variant. Greek voiced stops are optionally prenasalized, and the amplitude trajectory for the voice bar during closure suggests that younger children use a greater degree of nasal venting to create the aerodynamic conditions necessary for voicing lead. Taken together, the findings suggest that VOT must be supplemented by measurements of other language-specific acoustic properties to explain the mastery pattern of voiced stops in some languages.