Velar palatalization is a common sound change involving a velar stop becoming a palatal affricate or fricative before a front vocoid. To gain insight into its phonetic mechanisms, we test two hypotheses about factors conditioning velar palatalization by comparing similar languages with and without the change: (1) the conditioning vowels are fronter in languages with the change, resulting in fronter closure of the velar through coarticulatory assimilation; or (2) languages with the change have stronger coarticulation of velar stops with following segments, resulting in greater fronting preceding front vocoids. Specifically, we compare two Chinese languages, Mandarin, which underwent velar palatalization in the 16th–17th centuries (k, kh, x became tɕ, tɕh, ɕ before high front vowels), and Cantonese, which has not undergone the change in the last millennium. Our results support hypothesis (1) but not (2). We find that Mandarin speakers produce i and y with a higher front cavity resonance (third formant for i and second formant for y), implying a shorter front cavity. Velar coarticulation, measured by locus equation slope, does not differ significantly between the two languages. This suggests that the phonetic preconditions of velar palatalization lie in an especially front articulation of the conditioning vocoid.
Amy Li (Wed,) studied this question.