Brain waves and prosodic structure

Abstract

There is a general agreement among prosodists about the definition of the sentence prosodic structure (PS) as a hierarchical organization of minimal prosodic units called accent phrases (AP). However, disagreements appear among models about the characteristics of the accent phrases, the role of their pitch accents, and the function of the prosodic structure itself in the linguistic system. This paper describes some properties of the Incremental Dependency (ID) model and their relations with brain waves, compared to the dominant Autosegmental-Metrical (AM) model. Instead of being described as containing only one content word (a noun, an adjective, a verb or an adverb), accent phrases in the Incremental Dependency model are defined by the time taken to pronounce them orally or process them in silent reading. In non-lexically stressed languages such as French or Korean, AP duration varies from 250 ms to about 1250 ms, values corresponding to the range of delta brain oscillations. This suggests that delta waves are involved in the coding and decoding of accent phrases. A eurhythmic process aiming to balance the duration of successive AP determines its actual duration within the limits of delta wave variations. Whereas the AM approach does not consider interactions between pitch accents, the ID model describes melodic movements of pitch accents as markers of dependency relations existing between accent phrases, relations which determine the sentence prosodic structure. Furthermore, while the AM model views the prosodic structure as an emanation of the sentence syntactic structure, the ID model considers the prosodic structure as independent from grammar and actually generated in the speech process chunk by chunk before syntax and lexical selection. The prosodic structure appears then as a syntactic preselection device to process quickly in real time the flow of information, given the limits of short-term memory for speech (about 3 seconds).