P centers, C centers, or what else?

Some questions concerning the underlying nature of the so-called P-center phenomenon (the acoustic anisochrony of rhythmically regularly produced/perceived sequences of monosyllables) are discussed in the light of recent EMG data from experiments with rhythmically produced /Cak/ syllables (with /C/ = /p/, /pf/, /pl/, /pt/, /pfl/). The differences between /p/ vs /pf/ syllables resemble the timing differences in the microbeam data of Browman and Goldstein [Haskins SR-93/94, 85–102 (1988)]. Whereas they found a stable timing relation between the “articulatory mean” of the initial consonants (termed C center) and the acoustical offset of the following vowel, in terms of their task dynamic description, however, the phase relations between consonant and vowel gestures should remain the same. This would result in a reduced stiffness of the vowel gesture for the syllables containing consonant clusters. The observations of the present study would also correspond to a reduction of stiffness for the vowel but the numerical data seem to contradict a stable phasing relation. In connection with the psychoacoustic interpretation of the P-center phenomenon, an argument is made against a strictly intrinsic timing interpretation (based on articulatory regularities) of the effects of rhythmical production/perception.