Are there facial correlates of Thai syllabic tones?

![CDATA[This paper deals with the influence of tones on syllabic articulation in Thai. Motion capturing of 24 facial points in the face of a female speaker was performed using an Optotrak system as she uttered 24 sets of syllabic tokens covering the five different tones of Thai 12 times each. After rigid and non-rigid movements had been separated, a PCA was conducted on the non-rigid data. In order to determine the influence of the tones on the facial movement the first PC reflecting the jaw opening was analyzed by aligning the derivatives of the first PCs with respect to the point of maximum velocity and averaging over all tokens of a syllable/tone combination. Analysis showed great similarities in the shapes of the resulting mean velocity contours. In some syllable sets, however, certain tones exhibited specific temporal alignments that were strongly correlated with the underlying syllable duration. This outcome suggests that certain syllable/tone combinations require a specific temporal alignment of articulatory and tonal gestures, though a consistent physiological explanation remains yet to be found.]]