Assimilation of nasals to the place of articulation of following consonants is a common and natural process among the world's languages. Recent phonological theory attributes this naturalness to the postulated geometry of articulatory features and the notion of spreading (McCarthy, 1988). Others view assimilation as a result of perception (Ohala, 1990), or as perceptually tolerated articulatory simplification (Kohler, 1990). Kohler notes that certain consonant classes (such as nasals and stops) are more likely than other classes (such as fricatives) to undergo place assimilation to a following consonant. To explain this pattern, he proposes that assimilation tends not to occur when the members of a consonant class are relatively distinctive perceptually, such that their articulatory reduction would be particularly salient. This explanation, of course, presupposes that the stops and nasals which undergo place assimilation are less distinctive than fricatives, which tend not to assimilate. We report experimental results that confirm Kohler's perceptual assumption: In the context of a following word initial stop, fricatives were less confusable than nasals or unreleased stops. We conclude, in agreement with Ohala and Kohler, that perceptual factors are likely to shape phonological assimilation rules.

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Proper names have several properties that create problems for speech recognition systems: the number of names is large and ever changing, names can be borrowed directly from other languages and may not conform to usual pronunciation rules, and the variety of pronunciations for names can be high. Because the set of proper names is so dynamic and machines are notoriously poor at phoneme recognition, a promising approach to designing a name recognition system is to incorporate statistical aspects of proper names (e.g., frequency, familiarity). Unfortunately, there exists relatively little data on the distribution of names. Ratings of familiarity and pronounceability were obtained for a randomly chosen sample of 199 surnames (from 80 987 entries in the Purdue phonebook) and 199 nouns (from Kucera–Francis). The ratings for nouns versus names are substantially different: nouns were rated as more familiar and easier to pronounce than surnames. Frequency and familiarity were more closely related in the proper name pool than the word pool, although the correlations were modest. Ratings of familiarity and pronounceability were highly related for both groups. The value of using frequency and the ratings of familiarity and pronounceability for predicting variations in actual pronunciations of words and names will be discussed.

Ratings of familiarity and pronounceability were obtained from a random sample of 199 sumames (selected from over 80,000 entries in the Purdue University phone book) and 199 nouns (from the Kucera-Francis, 1967, word database). The distributions of ratings for nouns versus names are substantially different: Nouns were rated as more familiar and easier to pronounce than sumames. Frequency and familiarity were more closely related in the proper name pool than the word pool, although both correlations were modest. Ratings of familiarity and pronounceability were highly related for both groups, A production experiment showed that rated pronounceability was highly related to the time taken to produce a name. These data confirm the common belief that there are differences in the statistical and distributional properties of words as compared to proper names. The value of using frequency and the ratings of familiarity and pronounceability for predicting variations in actual pronunciations of words and names are discussed.Recently, there has been an explosion of research regarding how people store and access proper names. The interest has been enough to generate a special issue ofthe journal Memory (Cohen & Burke, 1993) and at least one entire book on the subject (Valentine, Brennen, & Bredart, 1996). Much of the research has concentrated on how names and faces are related and on whether names and other words are represented separately in the lexicon. The studies reported here are meant to provide a corpus ofratings offamiliarity and pronounceability of surnames for use in experiments in human lexical access of names and for predicting variability in pronunciations ofnames for eventual use in applications such as computer speech recognizers.

Silent-center syllables are defined as CVC syllables in which the vowel nucleus is attenuated to silence, leaving three or four pitch periods of consonant transition at either edge of the syllable. Previous studies [W. Strange, J. Acoust. Soc. Am. 85, 2135–2153 (1989)] have shown that subjects are able to identify vowels in silent-center (SC) syllables with nearly the same accuracy as for full syllables. These results have been used to support the theory of dynamic specification, where vowels are conceived of as gestures having intrinsic timing parameters. The current studies suggest alternate interpretations of the SC results. In the first study, the perception of a set of SC syllables was compared with that of full syllables at several signal-to-noise ratios. Contrary to previous experiments, it was found that identification performance was significantly better for full syllables than for SCs across signal-to-noise ratios. This suggests that, given a more demanding perceptual task, identification is hindered when the vowel nucleus is not physically present in the signal. The second study was a replication in the visual mode of earlier studies on SC syllables [W. Strange, J. Acoust. Soc. Am. 85, 2135–2153 (1989)]. Here, spectrographic analogs of full, SC, and other altered syllables were created. Subjects performed a matching task. Results were similar to those from the auditory domain, suggesting that more general perceptual processes may underlie the pattern of responses in both sensory modalities.

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A growing body of evidence suggests that information about specific voices and specific exemplars of words is encoded in memory, as observed in results of implicit memory tasks in which subjects perform perceptual classification of stimuli. Hura [dissertation, University of Texas (1994)] found identification performance on silent-center (SC) syllables improved with previous exposure to corresponding full syllables, implying that representations of individual full syllables were encoded in memory and accessed in identification of SC stimuli. The current study investigates whether prior exposure to SC syllables improves performance on full syllables. Ten /bVt/ syllables spoken by multiple talkers were used to generate SC and hybrid SC stimuli (which combine the initial CV transition from one talker and the final VC transition from another). A subset of SC syllables, varying for identity of talker or vowels presented, were presented to subjects for identification. After a variable delay subjects were tested on a subset of full syllable stimuli. The magnitude of implicit memory effects in each case is assessed to address the claim that dynamic vowel information is speaker independent as suggested by the theory of dynamic specification.

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