Natural Referent Vowel (NRV) framework: An emerging view of early phonetic development

Abstract

The goal of this paper is to provide an overview of an emerging new framework for understanding early phonetic development -The Natural Referent Vowel (NRV) framework. The initial support for this framework was the finding that directional asymmetries occur often in infant vowel discrimination. The asymmetries point to an underlying perceptual bias favoring vowels that fall closer to the periphery of the F1/F2 vowel space. In Polka & Bohn (2003) we reviewed the data on asymmetries in infant vowel perception and proposed that certain vowels act as natural referent vowels and play an important role in shaping vowel perception. In this paper we review findings from studies of infant and adult vowel perception that emerged since Polka & Bohn 2003, from other labs and from our own work, and we formally introduce the NRV framework. We outline how this framework connects with linguistic typology and other models of speech perception and discuss the challenges and promise of NRV as a conceptual tool for advancing our understanding of phonetic development.

Directional asymmetries reveal a universal bias in adult vowel perception

“…Polka and Bohn (2003) initially proposed that this early vowel bias plays an important role in the development of vowel perception by establishing stable referents that help young infants attend to and differentiate vowels during the period when they are learning phonetic categories. Broadly consistent with this idea, more recent studies have shown that linguistic experience fine-tunes this initial vowel bias to optimize access to native-language vowel categories during speech processing (Polka & Werker, 1994;Polka & Bohn, 2011;Pons, Albareda-Castellot, Sebastián-Gallés, 2012;Dufour, Brunelliere, & Nguyen, 2013;Tyler, Best, Faber & Levitt, 2014). For example, with respect to German /u-/y/, monolingual English-speaking adults continue to show the same asymmetry as English-and German-learning infants, while German-speaking adults show symmetric (and near perfect) discrimination of this contrast (Polka & Bohn, 2011).…”

“…Broadly consistent with this idea, more recent studies have shown that linguistic experience fine-tunes this initial vowel bias to optimize access to native-language vowel categories during speech processing (Polka & Werker, 1994;Polka & Bohn, 2011;Pons, Albareda-Castellot, Sebastián-Gallés, 2012;Dufour, Brunelliere, & Nguyen, 2013;Tyler, Best, Faber & Levitt, 2014). For example, with respect to German /u-/y/, monolingual English-speaking adults continue to show the same asymmetry as English-and German-learning infants, while German-speaking adults show symmetric (and near perfect) discrimination of this contrast (Polka & Bohn, 2011). A similar pattern of developmental change emerged when Danish-speaking adults and Danish-learning infants were tested on a native contrast (i.e., Danish /e/-/ø/) and a non-native contrast (i.e., British English /ae/-/ɯ; Polka & Bohn, 2011), and when Spanish-and Catalan-learning infants were tested on discrimination of Catalan /i-e/ (Pons et al, 2012).…”

“…For example, with respect to German /u-/y/, monolingual English-speaking adults continue to show the same asymmetry as English-and German-learning infants, while German-speaking adults show symmetric (and near perfect) discrimination of this contrast (Polka & Bohn, 2011). A similar pattern of developmental change emerged when Danish-speaking adults and Danish-learning infants were tested on a native contrast (i.e., Danish /e/-/ø/) and a non-native contrast (i.e., British English /ae/-/ɯ; Polka & Bohn, 2011), and when Spanish-and Catalan-learning infants were tested on discrimination of Catalan /i-e/ (Pons et al, 2012). While a developmental shift from a universal to a language-specific pattern of vowel perception is expected for non-native contrasts, it is important to note that asymmetries in adults' perception of some native contrasts have also been observed (Repp, Healy, & Crowder, 1979;Cowan & Morse, 1986;Repp & Crowder, 1990).…”

“…On the basis of these findings, Polka and Bohn (2011) more recently formulated the Natural Referent Vowel (NRV) Framework. According to this framework, young infants from across cultures come to the task of language acquisition universally biased toward certain vowels which act as natural reference points (or perceptual attractors) within phonetic space.…”

Even at 4 months, a labial is a good enough coronal, but not vice versa

“…Asymmetries in prelexical infants' speech perception have played a major role in vowel discrimination research (see Polka & Bohn, 2011). However, the mechanisms proposed to underlie this perceptual bias (Schwartz, Abry, Boe, Menard, & Vallee, 2005) cannot easily be extrapolated to consonants, which are characterized by very different acoustic properties.…”