Do Infants Really Learn Phonetic Categories?

Early changes in infants’ ability to perceive native and nonnative speech sound contrasts are typically attributed to their developing knowledge of phonetic categories. We critically examine this hypothesis and argue that there is little direct evidence of category knowledge in infancy. We then propose an alternative account in which infants’ perception changes because they are learning a perceptual space that is appropriate to represent speech, without yet caring up that space into phonetic categories. If correct this new account has substantial implications for understanding early language development.

Calibration of Consonant Perception to Room Reverberation

Purpose We examined how consonant perception is affected by a preceding speech carrier simulated in the same or a different room, for different classes of consonants. Carrier room, carrier length, and carrier length/target room uncertainty were manipulated. A phonetic feature analysis tested which phonetic categories are influenced by the manipulations in the acoustic context of the carrier. Method Two experiments were performed, each with nine participants. Targets consisted of 10 or 16 vowel–consonant (VC) syllables presented in one of two strongly reverberant rooms, preceded by a multiple-VC carrier presented in either the same room, a different reverberant room, or an anechoic room. In Experiment 1, the carrier length and the target room randomly varied from trial to trial, whereas in Experiment 2, they were fixed within a block of trials. Results Overall, a consistent carrier provided an advantage for consonant perception compared to inconsistent carriers, whether in anechoic or differently reverberant rooms. Phonetic analysis showed that carrier inconsistency significantly degraded identification of the manner of articulation, especially for stop consonants and, in one of the rooms, also of voicing. Carrier length and carrier/target uncertainty did not affect adaptation to reverberation for individual phonetic features. The detrimental effects of anechoic and different reverberant carriers on target perception were similar. Conclusions The strength of calibration varies across different phonetic features, as well as across rooms with different levels of reverberation. Even though place of articulation is the feature that is affected by reverberation the most, it is the manner of articulation and, partially, voicing for which room adaptation is observed.

Exploring language dominance through code-switching: intervocalic voiced stop lenition in Afrikaans–Spanish bilinguals

The present study examines the relationship between the two grammars of bilingual speakers, the linguistic ecologies in which the L1 and L2 become active, and how these topics can be explored in a bilingual community undergoing L1 attrition. Our experiment focused on the production of intervocalic phonemic voiced stops for L1-Afrikaans/L2-Spanish bilinguals in Patagonia, Argentina. While these phonemes undergo systematic intervocalic lenition in Spanish (e.g., /b d ɡ/ > [β ð ɣ]), they do not in Afrikaans (e.g., /b d/ > [b d]). The bilingual participants in our study produced target Afrikaans and Spanish words in unilingual and code-switched speaking contexts. The results show that: (i) the participants produce separate phonetic categories in Spanish and Afrikaans; (ii) code-switching affects the production of the target sounds asymmetrically, such that L1 Afrikaans influences the production of L2 Spanish sounds but not vice versa; and (iii) this L1-to-L2 influence remains robust despite the instability of the L1 itself. Altogether, our findings speak to the persistence of a bilingual’s L1 phonological grammar despite cross-generational L1 attrition.

Early phonetic learning without phonetic categories: Insights from large-scale simulations on realistic input

Before they even speak, infants become attuned to the sounds of the language(s) they hear, processing native phonetic contrasts more easily than nonnative ones. For example, between 6 to 8 mo and 10 to 12 mo, infants learning American English get better at distinguishing English and [l], as in “rock” vs. “lock,” relative to infants learning Japanese. Influential accounts of this early phonetic learning phenomenon initially proposed that infants group sounds into native vowel- and consonant-like phonetic categories—like and [l] in English—through a statistical clustering mechanism dubbed “distributional learning.” The feasibility of this mechanism for learning phonetic categories has been challenged, however. Here, we demonstrate that a distributional learning algorithm operating on naturalistic speech can predict early phonetic learning, as observed in Japanese and American English infants, suggesting that infants might learn through distributional learning after all. We further show, however, that, contrary to the original distributional learning proposal, our model learns units too brief and too fine-grained acoustically to correspond to phonetic categories. This challenges the influential idea that what infants learn are phonetic categories. More broadly, our work introduces a mechanism-driven approach to the study of early phonetic learning, together with a quantitative modeling framework that can handle realistic input. This allows accounts of early phonetic learning to be linked to concrete, systematic predictions regarding infants’ attunement.

Calibration of consonant perception to room reverberation

PurposeWe examined how consonant perception is affected by a preceding speech carrier simulated in the same or a different room, for a broad range of consonants. Carrier room, carrier length, and carrier length/target room uncertainty were manipulated. A phonetic feature analysis tested which phonetic categories are most influenced by the acoustic context of the carrier.MethodTwo experiments were performed, each with 9 participants. Targets consisted of vowel-consonant (VC) syllables presented in one of 2 strongly reverberant rooms, preceded by a VC carrier presented either in the same room, a different reverberant room, or an anechoic room. In Experiment 1 the carrier length and the target room randomly varied from trial to trial while in Experiment 2 they were fixed within blocks of trials.ResultsCompared to the no-carrier condition, a consistent carrier provided only a small advantage for consonant perception, whereas inconsistent carriers disrupted performance significantly. For a different-room carrier, carrier length had an effect; performance dropped significantly in the 2-VC compared to the 4-VC carrier length. The only effect of carrier uncertainty was an overall drop in performance. Phonetic analysis showed that an inconsistent carrier significantly degraded identification of the manner of articulation, especially for stop consonants, and, in one of the rooms, also of voicing.ConclusionsCalibration of consonant perception to strong reverberation is exhibited through disruptions in perception when the room is switched. The strength of calibration varies across different consonants and phonetic features, as well as across rooms and durations of exposure to a given room.

The role of indexical cues in the distributional learning of phonetic categories.

Theories of the distributional learning of phonetic categories assume that input provides reliable distributional cues for the categorization of speech sounds. In the real world, however, not all talkers produce exactly the same distributions of speech sounds, and the talker-dependent variation may undermine the reliability of the distributional cues. In this study, we investigated how learners might overcome talker-dependent variation. Specifically, we tested whether adults can learn two phonetic categories from input in which talker-dependent variation introduces potential ambiguities into the categorization of speech sounds. The results suggest that they can overcome this kind of ambiguity by using indexical information (i.e., the identity of talkers).

Dominance, mode, and individual variation in bilingual speech production and perception

Early Spanish-English bilinguals and English controls were tested on the production and perception of negative, short-lag, and long-lag Voice Onset Time (VOT), VOT types spanning the Spanish and English phonetic categories: phonologically, negative and short-lag VOT stops are distinct phonemes in Spanish, but realizations of voiced stops in English. Dominance was critical: more English-dominant bilinguals produced more short-lag VOT stops in response to negative VOT stimuli, and were also less accurate than more balanced bilinguals at discriminating negative from short-lag VOT. Bilinguals performed similarly to monolinguals overall, but they produced more negative VOT tokens and shorter short-lag VOT in response to negative VOT. Their productions were also less well correlated with perception and showed more variation between individuals. These results highlight the variable nature of bilingual production and perception, and demonstrate the need to consider language dominance, individual variation, as well as modalities and tasks when studying bilinguals.