That speakers can vary their speaking rate is evident, but how they accomplish this has
hardly been studied. The effortful experience of deviating from one's preferred speaking rate
might result from shifting between different regimes (system configurations) of the speech
planning system. This study investigates control over speech rate through simulations of a
new connectionist computational model of the cognitive process of speech production, derived
from Dell, Burger and Svec’s (1997) model to fit the temporal characteristics of observed
speech. We draw an analogy from human movement: the selection of walking and running
gaits to achieve different movement speeds. Are the regimes of the speech production system
arranged into multiple ‘gaits’ that resemble walking and running?
During training of the model, different parameter settings are identified for different speech
rates, which can be conflated with the regimes of the speech production system. The
parameters can be considered to be dimensions of a high-dimensional ‘regime space’, in
which different regimes occupy different parts of the space.
In a single gait system, the regimes are qualitatively similar, but quantitatively different.
They are arranged along a straight line through regime space. Different points along this axis
correspond directly to different speaking rates. In a multiple gait system, the arrangement of
the regimes is more disperse, with no obvious relationship between the regions associated
with each gait.
After training, the model achieved good fits in all three speaking rates, and the parameter
settings associated with each speaking rate were different. The broad arrangement of the
parameter settings for the different speaking rates in regime space was non-axial, suggesting
that ‘gaits’ may be present in the speech planning system.