Presentations

Abstract

Speech rate is one of the more salient stylistic dimensions along which speech can vary. We present both sides of this story: how listeners make use of this variation to optimise speech perception, and how the speech production system is modulated to produce speech at different rates.

Listeners take speech rate variation into account by normalizing vowel duration or contextual speech rate: an ambiguous Dutch word /m?t/ is perceived as short /mAt/ when embedded in a slow context, but long /ma:t/ in a fast context. Many have argued that rate normalization involves low-level early and automatic perceptual processing. However, prior research on rate-dependent speech perception has only used explicit recognition tasks to investigate the phenomenon, involving both perceptual processing and decision making. Speech rate effects are induced by both local adjacent temporal cues and global non-adjacent cues. In this talk, I present evidence that local rate normalization takes place, at least in part, at a perceptual level, and even in the absence of an explicit recognition task. In contrast, global effects of speech rate seem to involve higher-level cognitive adjustments, possibly taking place at a later decision-making level.

That speakers can vary their speech rate is evident, but how they accomplish this has hardly been studied. Consider this analogy: when walking, speed can be continuously increased, within limits, but to speed up further, humans must run. Are there multiple qualitatively distinct speech 'gaits' that resemble walking and running? Or is control achieved solely by continuous modulation of a single gait? These possibilities are investigated through simulations of a new connectionist computational model of the cognitive process of speech production. The model has parameters that can be adjusted to fit the temporal characteristics of natural speech at different rates. During training, different clusters of parameter values (regimes) were identified for different speech rates. In a one gait system, the regimes used to achieve fast and slow speech are qualitatively similar, but quantitatively different. In a multiple gait system, there is no linear relationship between the parameter settings associated with each gait, resulting in an abrupt shift in parameter values to move from speaking slowly to speaking fast. After training, the model achieved good fits in all three speech rates. The parameter settings associated with each speech rate were not linearly related, suggesting the presence of cognitive gaits, and thus that speakers make use of distinct cognitive configurations for different speech rates.

Abstract

Speech rate is one of the more salient stylistic dimensions along which speech can vary. We present both sides of this story: how the speech production system is modulated to produce speech at different rates, and how listeners make use of this variation to optimise speech perception.

Joe Rodd: Speakers switch between qualitatively different cognitive ‘gaits’ to produce speech at different rates

That speakers can vary their speech rate is evident, but how they accomplish this has hardly been studied. Consider this analogy: when walking, speed can be continuously increased, within limits, but to speed up further, humans must run. Are there multiple qualitatively distinct speech 'gaits' that resemble walking and running? Or is control achieved solely by continuous modulation of a single gait? These possibilities are investigated through simulations of a new connectionist computational model of the cognitive process of speech production. The model has parameters that can be adjusted to fit the temporal characteristics of natural speech at different rates. During training, different clusters of parameter values (regimes) were identified for different speech rates. In a one gait system, the regimes used to achieve fast and slow speech are qualitatively similar, but quantitatively different. In a multiple gait system, there is no linear relationship between the parameter settings associated with each gait, resulting in an abrupt shift in parameter values to move from speaking slowly to speaking fast. After training, the model achieved good fits in all three speech rates. The parameter settings associated with each speech rate were not linearly related, suggesting the presence of cognitive gaits, and thus that speakers make use of distinct cognitive configurations for different speech rates.

Merel Maslowski: Listeners use the speech rate context to tune their speech perceptions

Listeners take speech rate variation into account by normalizing vowel duration or contextual speech rate: an ambiguous Dutch word /m?t/ is perceived as short /mAt/ when embedded in a slow context, but long /ma:t/ in a fast context. Many have argued that rate normalization involves low-level early and automatic perceptual processing. However, prior research on rate-dependent speech perception has only used explicit recognition tasks to investigate the phenomenon, involving both perceptual processing and decision making. Speech rate effects are induced by both local adjacent temporal cues and global non-adjacent cues. In this talk, I present evidence that local rate normalization takes place, at least in part, at a perceptual level, and even in the absence of an explicit recognition task. In contrast, global effects of speech rate seem to involve higher-level cognitive adjustments, possibly taking place at a later decision-making level.

Abstract

It is evident that speakers can freely vary stylistic features of their speech, such as speech rate, but how they accomplish this has hardly been studied, let alone implemented in a formal model of speech production. Much as in walking and running, where qualitatively different gaits are required cover the gamut of different speeds, we might predict there to be multiple qualitatively distinct configurations, or ‘gaits’, in the speech planning system that speakers must switch between to alter their speaking rate or style. Alternatively, control might involve continuous modulation of a single ‘gait’. We investigate these possibilities by simulation of a connectionist computational model which mimics the temporal characteristics of observed speech. Different ‘regimes’ (combinations of parameter settings) can be engaged to achieve different speaking rates.

The model was trained separately for each speaking rate, by an evolutionary optimisation algorithm. The training identified parameter values that resulted in the model to best approximate syllable duration distributions characteristic of each speaking rate.

In one gait system, the regimes used to achieve fast and slow speech are qualitatively similar, but quantitatively different. In parameter space, they would be arranged along a straight line. Different points along this axis correspond to different speaking rates. In a multiple gait system, this linearity would be missing. Instead, the arrangement of the regimes would be triangular, with no obvious relationship between the regions associated with each gait, and an abrupt shift in parameter values to move from speeds associated with ‘walk-speaking’ to ‘run-speaking’.

Our model achieved good fits in all three speaking rates. In parameter space, the arrangement of the parameter settings selected for the different speaking rates is non-axial, suggesting that ‘gaits’ are present in the speech planning system.