Lecture: Neuronal modulations in early lexical acquisition
Methodological assessment and theoretical implications
To understand how speakers acquire a lexicon and expand their vocabulary repertoire all throughout ages and development phases, it is crucial to go to the nitty-gritty of experimentation. Exploring these questions at the cognitive level calls for the use neuroimaging methods developed in the field of neurolinguistics. As of today, the neuronal mechanisms for the encoding of linguistic expressions in long-term memory are still ill-understood. One demographic group of interest for studying this question is that of infants, due to their higher levels of synaptic plasticity. How is it that the brain deals with memorization of native and non-native expressions, that is, phonologically legal or illicit forms? How do other cognitive mechanisms, such as attention, modulate this integration process? What are the effects of language-specific variables, such as phonemic quality and frequency, lexical exposure and syllabic form, on early learning of novel entries?
In this talk, I would like to present our ongoing EEG project at the Integrative Neuroscience and Cognition Center (Paris Descartes University) supervised by Pia Rämä, on early lexical acquisition in 24-month-olds. I’ll describe our specific goals and methodology in this small project, not only as a way to get feedback for further improvement (given that the testing phase is still ongoing) but also as a way to open a broader discussion on how it is that linguists contribute to and integrate neuroscientific data for their own theoretical formulation, model-testing and the plausibility of the postulated natural kinds of language.
Here, we investigated neural mechanisms underlying rapid on-line novel word acquisition in subjects by measuring event-related potentials (ERPs) in response to novel and familiar words during a passive listening task. Monolingual 24-month-olds were presented with familiar legal words and novel pseudo-words. Following Shtyrov et. al (2011), we designed minimally paired known words and pseudo-words with a CV_CV structure, in which the first syllables were matched and the disambiguation point was established at the onset of the second syllable. Acoustic properties, language-specific and age-specific frequencies of the phonemes, known lexical items, and all CV concatenations, were controlled for. The ERPs were averaged in response to word types and three stages of exposure (early, middle and late stages of total exposure (15-20 minutes)).
Our results seem to indicate that the ERPs are modulated differentially in response to known and novel words: the responses to novel words are enhanced while the responses to known words remain stable during the course of the experiment, similarly to earlier findings in adults (Shtyrov et al., 2010) and school-aged children (Partanen et al., 2017). These data suggest that the ERP modulation might be related to lexical learning in the developing brain.
This may serve as an opportunity to more openly discuss some concepts of neurolinguistic research, in particular those pertaining to EEG and the study of neuronal oscillations involved in language acquisition. I will try to integrate some elements from linguistic theory that are not from acquisition studies proper, but do make assumptions about how linguistic elements must be stored and retrieved in cognition. Do these data resonate with what we know about learning at the neuronal level? Should models in linguistics be fundamentally separate from brain models of language processing? More generally, how should we formulate a productive relation between theoretical linguistics and experimental neuroscientific research to more accurately model the dynamics of natural language?