Perceptual assimilation and discrimination of non-native vowel contrasts.

Research on language-specific tuning in speech perception has focused mainly on consonants, while that on non-native vowel perception has failed to address whether the same principles apply. Therefore, non-native vowel perception was investigated here in light of relevant theoretical models: the Perceptual Assimilation Model (PAM) and the Natural Referent Vowel (NRV) framework. American-English speakers completed discrimination and native language assimilation (categorization and goodness rating) tests on six nonnative vowel contrasts. Discrimination was consistent with PAM assimilation types, but asymmetries predicted by NRV were only observed for single-category assimilations, suggesting that perceptual assimilation might modulate the effects of vowel peripherality on non-native vowel perception.

Computational simulation of CV combination preferences in babbling.

There is a tendency for spoken consonant-vowel (CV) syllables, in babbling in particular, to show preferred combinations: labial consonants with central vowels, alveolars with front, and velars with back. This pattern was first described by MacNeilage and Davis, who found the evidence compatible with their "frame-then-content" (F/C) model. F/C postulates that CV syllables in babbling are produced with no control of the tongue (and therefore effectively random tongue positions) but systematic oscillation of the jaw. Articulatory Phonology (AP; Browman & Goldstein) predicts that CV preferences will depend on the degree of synergy of tongue movements for the C and V. We present computational modeling of both accounts using articulatory synthesis. Simulations found better correlations between patterns in babbling and the AP account than with the F/C model. These results indicate that the underlying assumptions of the F/C model are not supported and that the AP account provides a better and account with broader coverage by showing that articulatory synergies influence all CV syllables, not just the most common ones.

Biomechanically preferred consonant-vowel combinations fail to appear in adult spoken corpora.

Certain consonant/vowel (CV) combinations are more frequent than would be expected from the individual C and V frequencies alone, both in babbling and, to a lesser extent, in adult language, based on dictionary counts: Labial consonants co-occur with central vowels more often than chance would dictate; coronals co-occur with front vowels, and velars with back vowels (Davis & MacNeilage, 1994). Plausible biomechanical explanations have been proposed, but it is also possible that infants are mirroring the frequency of the CVs that they hear. As noted, previous assessments of adult language were based on dictionaries; these "type" counts are incommensurate with the babbling measures, which are necessarily "token" counts. We analyzed the tokens in two spoken corpora for English, two for French and one for Mandarin. We found that the adult spoken CV preferences correlated with the type counts for Mandarin and French, not for English. Correlations between the adult spoken corpora and the babbling results had all three possible outcomes: significantly positive (French), uncorrelated (Mandarin), and significantly negative (English). There were no correlations of the dictionary data with the babbling results when we consider all nine combinations of consonants and vowels. The results indicate that spoken frequencies of CV combinations can differ from dictionary (type) counts and that the CV preferences apparent in babbling are biomechanically driven and can ignore the frequencies of CVs in the ambient spoken language.

Response to MacNeilage and Davis and to Oller.

The article by MacNeilage and Davis in this issue, entitled "In Defense of the 'Frames, then Content' (FC) Perspective on Speech Acquisition: A Response to Two Critiques" appears to assume that the only alternative to segment-level control is oscillation specifically of the jaw; however, other articulators could be oscillated by infants as well. This allows the preferred CV combinations to emerge without positing a level of segmental control in babbling. Their response does not address our modeling work, which, rather similarly to Davis's own modeling (Serkhane, Schwartz, Boë, Davis, & Matyear, 2007), shows little support for the Frame-then-Content (F/C) account. Our results show substantial support for the Articulatory Phonology (AP) one. A closer look at feeding in infants shows substantial control of the tongue and lips, casting further doubt on the foundation of the F/C account.

An Articulatory Phonology Account of Preferred Consonant-Vowel Combinations.

Certain consonant/vowel combinations (labial/central, coronal/front, velar/back) are more frequent in babbling as well as, to a lesser extent, in adult language, than chance would dictate. The "Frame then Content" (F/C) hypothesis (Davis & MacNeilage, 1994) attributes this pattern to biomechanical vocal-tract biases that change as infants mature. Articulatory Phonology (AP; Browman and Goldstein 1989) attributes preferences to demands placed on shared articulators. F/C implies that preferences will diminish as articulatory control increases, while AP does not. Here, babbling from children at 6, 9 and 12 months in English, French and Mandarin environments was examined. There was no developmental trend in CV preferences, although older ages exhibited greater articulatory control. A perception test showed no evidence of bias toward hearing the preferred combinations. Modeling using articulatory synthesis found limited support for F/C but more for AP, including data not originally encompassed in F/C. AP thus provides an alternative biomechanical explanation.

VOT in the babbling of French- and English-learning infants.

Different languages use voice onset time (VOT) in different ways to signal the voicing contrast, for example, short lag/long lag (English) vs. prevoiced/short lag (French). Also, VOT depends on place of articulation, with labial VOTs being shorter than velar and alveolar and, sometimes, alveolar being shorter than velar. Here we examine the VOT in babbled utterances of five French-learning and five English-learning infants at ages 9 and 12 months. There was little or no difference between the languages for duration of positive VOTs, which were usually in the "short lag" range. The duration of prevoicing also did not differ between languages, but the proportion of prevoiced utterances did (French-learning infants: 44.2% prevoicing; English-learning: 14.3%). Labial, alveolar and velar stops differed in VOT, with alveolar longer than labial and velar longer than alveolar, suggesting a mechanical cause. The lack of long-lag VOT indicates that the English-learning infants have not mastered aspiration by 12 months. The different proportions of prevoicing, however, suggest that the French-learning infants attempt to imitate the prevoicing that is used frequently (and contrastively) in their native language environment. The results suggest that infants are sensitive to the voicing categories of the ambient language but that they may be able to control prevoicing more successfully than aspiration.