resonant dynamics of speech perception

[Stephen Grossberg <steve@xxxxxxxxxx>]

The following article is now available at
http://www.cns.bu.edu/Profiles/Grossberg in HTML, PDF, and  Gzipped
Postscript. It suggests how some challenging psychophysical data that
involve  backward effects in time can be quantitatively explained.

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  resonance, context effects, consonant perception, neural
network, silence duration, working memory, categorization