Origin of the consonant/vowel asymmetry in lexical processing – ORICONVO

Research in speech perception has shown that infants have early capacities to discriminate consonantal and vocalic contrasts and quickly become attuned to the properties of their native language. An asymmetry in sensitivity between consonants and vowels in word learning is first reported in French-learning infants, to the advantage of consonants (C-bias), suggesting a link between phonological and lexical acquisition that might facilitate language learning. However subsequent studies showed that English- and Danish-learning infants display no early bias or higher sensitivity to vowels. The C-bias might thus be modulated in early infancy. It might be present at birth, in which case it would decrease or disappear in childhood for languages like English and Danish. Or it might emerge during development, as a result of infants’ linguistic experience with their native language, raising the issues of when and how it is acquired. At present, we know very little about the possible developmental trajectory of the C-bias in lexical processing. For the first time, the present project will address this issue using an integrated approach of early lexically-related speech perception abilities during the first year of life. It will focus on French, a language for which the C-bias has been firmly established from 14 months of age till adulthood, although this work is also planned in collaboration with colleagues studying similar phenomena in English-learning infants.
Three different accounts for the C-bias will be examined in this developmental project: (1) The innate bias hypothesis - infants start processing consonants and vowels as distinctive linguistic categories from the onset of language acquisition; (2) The acoustic/phonetic hypothesis - the C-bias emerges during the first year of life due to consonant/vowel acoustic differences, as consonants are usually shorter, less periodic, and tend to be perceived more categorically than vowels. These acoustic differences would lead to the construction of two phonologically distinct categories in toddlers, which would lead to the observation of a phonological consonant bias in young children and adults; and (3) The lexical hypothesis - the C-bias is in fact a reflection of the linguistic experience of the learners at the lexical level, from which they will learn that consonants are better, more informative cues to lexical identity than vowels once they have acquired a large enough lexicon. For learners of languages that have more vocalic sounds than consonants, it is predicted that the C-bias will not emerge.
Data from French infants from birth to 11 months will be collected in Paris. TASKs 1-4 will test the comparative use of consonantal and vocalic information in lexically-related processing by monolingual term infants. TASKs 1 and 2 will focus on the processing of word forms without meaning, while TASKs 3 and 4 will focus on the processing of known words. The results obtained will be used as a comparison point to investigate similar issues in bilingual term infants (TASK5) and healthy monolingual preterm infants (TASK6). The studies will rely on an array of behavioral (HPP), electrophysiological (ERPs) and neuroimaging (NIRS) techniques. Taken together, these studies will bring crucial information regarding the origins of the C-bias in lexical processing, and regarding the interaction between innate perceptual capacities and linguistic input, in typical monolingual situations, but also in situations in which infants are learning more than one language, or starting to learn language with an immature brain. Our findings will help confirm/disconfirm the three different hypotheses presented above (innate vs. acoustic/phonetic vs. lexical). The strength of the project lies also in its cross-disciplinary approach (developmental psychology, linguistics, neuroscience, pediatrics/neonatology), and its contribution to the training of young researchers (PhDs and postdocs).