Neural mechanisms for phonological alternation with high and low productivity - a case study on tone sandhi

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

Of the 7,000 or so languages spoken in the world today, a conservative estimate of around half of them are tonal, in that the use of pitch itself may change the meaning of a word. This list includes languages that play key roles in the economy and national security of the US such as Chinese and Vietnamese as well as many Native American languages such as Navajo and Cherokee. A better understanding of the linguistic properties of these languages is a meaningful first step in increasing the communication efficiency with speakers of these languages and the development of better learning materials for these languages for native speakers of English. This project investigates the linguistic patterns of tone in two Chinese languages--Mandarin and Taiwanese--using state-of-the-art neurolinguistic techniques to shed light on how words with tones are represented in the speakers' brains. It contributes methodological innovations that will allow the different stages of the production processing of tone to be tracked by neurological measures. Moreover, this project involves international collaboration between a US institution and two prominent neurolinguistic laboratories in Hong Kong and Taiwan. The established connections will provide educational opportunities for students both in the US and internationally. This project focuses on tonal alternation patterns whereby a tone takes different phonological forms in different contexts, also known as "tone sandhi." Behavioral studies have shown that tone sandhi patterns extend to novel words in different ways, i.e., have different productivity, depending on the phonological nature of the pattern. This suggests that different mechanisms may be involved in the processing of this type of phonological alternation. This project uses event-related potentials (ERPs) to examine the time-course of the encoding of a number of tone sandhi patterns in Mandarin and Taiwanese in speech production. It is hypothesized that unproductive sandhi patterns are primarily subserved by a lexical mechanism that engages neural activities in an earlier time window of lexical retrieval (approximately 150-225 ms after the initiation of production), while productive sandhi patterns are primarily subserved by a computation mechanism that engages neural activities in a later time-window of phonological encoding (400-600 ms). It is also hypothesized that the neural activities of the lexical mechanism are sensitive to lexical frequency, while those of the computation mechanism are less so. This project will be the first to investigate the neural activities underlying the putative computation vs. lexical mechanisms associated with productive and unproductive phonological alternations. The increased understanding of the neural encoding of phonological alternation will inform both the theoretical models of speech production and formal models of phonological competence. Findings of this project can also be linked to issues of morphological decompositionality such as regularity and semantic transparency to achieve a fuller understanding of the neural bases of linguistic productivity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.