The phonetic landscape in infant consonant perception is an uneven terrain

Abstract

Previous research revealing universal biases in infant vowel perception forms the basis of the Natural Referent Vowel (NRV) framework (Polka & Bohn, 2011). To explore the feasibility of extending this framework to consonant manner perception, we investigated perception of the stop vs. fricative consonant contrast /b/-/v/ to test the hypothesis that young infants will display a perceptual bias grounded in the acoustic-phonetic properties of these sounds. We examined perception of stop-initial /bas/ and fricative-initial /vas/ syllables in English-learning and French-learning 5- to 6-month-olds. The /b/ and /v/ sounds distinguish words in English and French but have different distributional patterns; in spoken English /b/ occurs more frequently than /v/ whereas in spoken French /v/ occurs more frequently than /b/. A perceptual bias favoring /b/ over /v/ emerged in two experiments. In Experiment 1, a directional asymmetry was observed in discrimination; infants noticed when /vas/ changed to /bas/ but not when /bas/ changed to /vas/. In Experiment 2, a robust listening preference favoring stop-initial /bas/ was evident in responses from the same infants. This is the first study to show a perceptual bias related to consonant manner and to directly measure a consonant perception bias within the same infants. These data encourage further efforts to extend the NRV principles to perception of consonant manner. These findings indicate that we need to reform our view of infant speech perception to accommodate the fact that both discrimination abilities and biases shape speech perception during infancy.

Infants and Adults Use Visual Cues to Improve Detection and Discrimination of Speech in Noise

“…We were surprised to find that infants in our study had so much more difficulty discriminating target /lu/ from background /mu/ than discriminating target /gu/ from background /mu/, given that both targets differ from the background in both place and manner of articulation. These results are consistent with Nam and Polka's (2016) suggestion that, in early infancy, some phonetic units-particularly stops-have higher perceptual salience than others. This "stop bias" in early infancy appears to be grounded in the acoustic-phonetic properties of stops.…”

Directional asymmetries reveal a universal bias in adult vowel perception

“…Recent evidence indicates that this may also be the case in the perception of consonants. Specifically, Nam & Polka (2016) found that young infants from across different linguistic communities are initially biased toward stop consonants over fricative consonants, and that this bias continues to operate within adult language users (see also, Nam, 2015). At the present time, developmental theories, such as NLM (Kuhl et al, 2008), have focused almost exclusively on explicating how native-language experience alters speech perception, but such models will ultimately need to provide a more complete account of how universality and language-specificity fit together.…”

Context and perceptual asymmetry effects on the mismatch negativity (MMNm) to speech sounds: an MEG study

“…In this light, it is relevant to consider recent extensions of the Natural Referent Vowel (NFR) framework (Polka & Bohn, 2003; which have attempted to include consonants as well (Bundgaard-Nielsen, Baker, Kroos, Harvey, & Best, 2015;Nam, 2014;Nam & Polka, 2016), suggesting that one member of a contrast serves as a perceptual anchor (or referent) to the other during language acquisition by virtue of that member's psychoacoustic saliency. For vowels, these referents are at the extremes of the vowel inventory, and for consonants, stops have tentatively been suggested as referents for fricatives due to their steeper attack time (Nam, 2014;Nam & Polka, 2016), and alveolar stops as referents for retroflex and dental stops (Bundgaard- Nielsen et al, 2015). It may thus be that there is a psycholinguistic relevance to lowlevel feature detectors potentially sensitive to broad-spectrum noise in terms of increased psychoacoustic saliency for aspirated over non-aspirated sounds.…”