Resonant Dynamics of Speech Perception

[Stephen Grossberg]

The following article is now available at 
http://www.cns.bu.edu/Profiles/Grossberg in HTML, PDF, and  Gzipped 
Postscript.

Grossberg, S. and Myers, C.W.  The resonant dynamics of speech 
perception: Interword integration and duration-dependent backward 
effects.
Psychological Review.

ABSTRACT: How do listeners integrate temporally distributed phonemic 
information into coherent representations of syllables and words? 
During fluent speech perception, variations in the durations of 
speech sounds and silent pauses can produce different perceived 
groupings. For example, increasing the silence interval between the 
words "gray chip" may result in the percept "great chip", whereas 
increasing the duration of fricative noise in "chip" may alter the 
percept to "great ship" (Repp et al., 1978).  The ARTWORD neural 
model quantitatively simulates such context-sensitive speech data. 
In ARTWORD, sequential activation and storage of phonemic items in 
working memory provides bottom-up input to unitized representations, 
or list chunks, that group together sequences of items of variable 
length.  The list chunks compete with each other as they dynamically
integrate this bottom-up information.  The winning groupings feed 
back to provide top-down support to their phonemic items.  Feedback 
establishes a resonance which temporarily boosts the activation 
levels of selected items and chunks, thereby creating an emergent 
conscious percept.  Because the resonance evolves more slowly than 
working memory activation, it can be influenced by information 
presented after relatively long intervening silence intervals.  The 
same phonemic input can hereby yield different groupings depending on 
its arrival time.  Processes of resonant transfer and competitive 
teaming help determine which groupings win the competition. 
Habituating levels of neurotransmitter along the pathways that 
sustain the resonant feedback lead to a resonant collapse that 
permits the formation of subsequent resonances.

Keywords: speech perception, word recognition, consciousness, 
adaptive  esonance, context effects, consonant perception, neural 
network, silence duration, working memory, categorization, clustering.