English obstruent perception : The content of the p - map and its relationship to natural class structure

This paper reports a series of analyses of consonant identification data from Cutler, Weber, Smits, & Cooper (2004) and which empirically derive perceptual similarity to determine how it compares with feature-based models of phoneme similarity. A model in which minimal contrast structure is equivalent to perceptual structure provides a baseline 'null hypothesis'. This baseline model is compared to 1) an empirically fitted choice model that does not require intersegment similarity to bear any particular relation to feature structure, 2) models which add an explicit interaction between features, and 3) a set-theoretic model in which feature structure relates to perceptual structure via the number of each pair of segments’ shared and non-shared natural classes (the Natural Class Similarity Model, Frisch 1996). These model comparisons indicate that features interact pervasively in perception and that syllable position modulates these interactions. Pairs of similarity parameters were then compared across the listeners in order to identify contrasts that systematically differ from one another in similarity (which we define as a failure in Feature Equivalence), and contrasts that systematically differ in similarity depending on the segments in which the contrast appears (which we define as a failure in Feature Independence). Some of these identified differences could be accounted for by the set theoretic model, though this model systematically underestimates the distinctiveness of sibilants from other segments, does not account for the robustness of coda voicing contrasts, and overestimates the distinctiveness of dental fricatives. Finally, multidimensional scaling analyses indicate that the expected phonological contrast structure was present in the confusion patterns, despite the pervasive and robust presence of irregularities. The results robustly document a pattern of perceptual irregularity in the face of an overall pattern of featural contrast structure, and are discussed in terms of a number of factors involved in relating perceptual confusability to phonological systems.