Articulatory and perceptual aspects of fricative-stop coarticulation: a pilot study

This paper is concerned with the influence of a preceding fricative on the production and perception of a stop consonant. In a well-known series of experiments (Mann & Repp, 1981; Repp & Mann, 1981, 1982), Mann and Repp showed that, when preceded by a fricative, an ambiguous stop acoustically halfway between /W/ and /N/ is identified differently depending on the place of articulation of the fricative. Specifically, listeners tend to identify stops more frequently as velars following / V/ than following /6/. This effect was shown to occur regardless of the presence/absence of a syllable boundary between the two consonants. It also appeared to decrease gradually in magnitude as a silence of increasing duration was inserted after the fricative, although it was still significant with silent gaps as long as 375 ms. As the listeners' responses were affected by both the specific acoustic structure of the fricative and its perceived category, it was suggested that the perceptual mechanism responsible for this effect was partly continuous and partly categorical, i.e. operated both before and after phonetic categorisation. These findings were accounted for in the framework of the motor theory of speech perception (see Liberman, 1996, for a recent synthesis). In this view, contextdependent variations in the perceived place of articulation of a stop demonstrate that some “tacit knowledge” of articulatory dynamics is involved in processing speech sounds. It was assumed that fricatives have an influence on how a following stop is produced, and, more particularly, that the place of articulation of a velar stop is shifted forward in the context of /V/. As the perceptual effect observed goes, as it were, in the opposite direction (more velar responses following / V/ than following /6/), this tends to indicate that compensatory adjustments are made in the identification of a stop depending on the adjacent fricative. In other words, a perceptual mechanism of some kind was assumed to be employed to factor out coarticulatory interactions between the fricative and the stop. For this explanation to be valid, one has to show that / V/ does induce a shift in the place of articulation of a following velar. To our knowledge however, there is still little data available on fricative-stop coarticulation. In an acoustic investigation involving eight speakers of American English, Repp and Mann (1982) measured the formant onset frequencies following the stop release in utterances such as [ VW$], [VN$], [6W$], [6N$], but their results proved to be difficult to interpret. The F3 onset frequency was higher following /V/ than following /6/, as predicted, but the fricative had no clear effect on the onset frequency of F2, and the pattern observed for F4 was at variance with MR Malecot & Chermak, 1966; Schwartz, 1967; Uldall, 1964) were mainly concerned with the role of fricative transitions as cues to the place of articulation of the following stop. Patterns of coarticulation in fricative-stop sequences do not seem to have been studied extensively in a direct manner, by gathering articulatory data (although this issue is partially addressed in Byrd, 1996, and in Borden & Gay, 1979). This is somewhat