Computational modelling of category stability in segment pairs participating in perceptual asymmetry

Abstract

Certain unidirectional sound changes show a similarity to the laboratory phenomenon of asymmetrical misperception. The unidirectionality of these processes mirror the dissimilar confusion rates of the two segments. Despite the similarity of these processes, it is not clear what role perceptual asymmetry plays in conditioning these changes. This study employs modeling to simulate change in the characteristics of consonant pairs whose confusion rates pattern with a unidirectional sound change: /k/-to-/t/ (before /i/) and /k/-to-/p/ (before /u/). Ten native AmEng speakers were recorded producing CVC words, where the initial consonant was /p/, /t/, or /k/ and the vowel varied in height and backness. Reduced and unreduced variants were elicited. Acoustically relevant features distinguishing /k/ from /t/ and /k/ from /p/ were identified using random forests. Reduced productions of /k/ and /p/ and /k/ and /t/, respectively, show higher acoustic similarity in vocalic contexts favoring increased confusability. This tendency toward acoustic similarity is predicted to condition category convergence. However, a language learner’s category may be better informed by tokens that show less acoustic similarity to tokens of another category, predicted to condition divergence. Modelled results suggest that the stability of phonetic categories is sensitive to the relative weighting of these two forces.Certain unidirectional sound changes show a similarity to the laboratory phenomenon of asymmetrical misperception. The unidirectionality of these processes mirror the dissimilar confusion rates of the two segments. Despite the similarity of these processes, it is not clear what role perceptual asymmetry plays in conditioning these changes. This study employs modeling to simulate change in the characteristics of consonant pairs whose confusion rates pattern with a unidirectional sound change: /k/-to-/t/ (before /i/) and /k/-to-/p/ (before /u/). Ten native AmEng speakers were recorded producing CVC words, where the initial consonant was /p/, /t/, or /k/ and the vowel varied in height and backness. Reduced and unreduced variants were elicited. Acoustically relevant features distinguishing /k/ from /t/ and /k/ from /p/ were identified using random forests. Reduced productions of /k/ and /p/ and /k/ and /t/, respectively, show higher acoustic similarity in vocalic contexts favoring increased confusability. Thi...