Publications

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  • Rodd, J., Bosker, H. R., Ernestus, M., Alday, P. M., Meyer, A. S., & Ten Bosch, L. (2020). Control of speaking rate is achieved by switching between qualitatively distinct cognitive ‘gaits’: Evidence from simulation. Psychological Review, 127(2), 281-304. doi:10.1037/rev0000172.

    Abstract

    That speakers can vary their speaking 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 by continuous modulation of a single gait? This study investigates these possibilities through simulations of a new connectionist computational model of the cognitive process of speech production, EPONA, that borrows from Dell, Burger, and Svec’s (1997) model. The model has parameters that can be adjusted to fit the temporal characteristics of speech at different speaking rates. We trained the model on a corpus of disyllabic Dutch words produced at different speaking rates. During training, different clusters of parameter values (regimes) were identified for different speaking rates. In a 1-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 speaking rates. The parameter settings associated with each speaking rate were not linearly related, suggesting the presence of cognitive gaits. Thus, we provide the first computationally explicit account of the ability to modulate the speech production system to achieve different speaking styles.

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  • Ernestus, M. (2012). Segmental within-speaker variation. In A. C. Cohn, C. Fougeron, & M. K. Huffman (Eds.), The Oxford handbook of laboratory phonology (pp. 93-102). New York: Oxford University Press.
  • Hanique, I., & Ernestus, M. (2012). The processes underlying two frequent casual speech phenomena in Dutch: A production experiment. In Proceedings of INTERSPEECH 2012: 13th Annual Conference of the International Speech Communication Association (pp. 2011-2014).

    Abstract

    This study investigated whether a shadowing task can provide insights in the nature of reduction processes that are typical of casual speech. We focused on the shortening and presence versus absence of schwa and /t/ in Dutch past participles. Results showed that the absence of these segments was affected by the same variables as their shortening, suggesting that absence mostly resulted from extreme gradient shortening. This contrasts with results based on recordings of spontaneous conversations. We hypothesize that this difference is due to non-casual fast speech elicited by a shadowing task.
  • Hanique, I., & Ernestus, M. (2012). The role of morphology in acoustic reduction. Lingue e linguaggio, 2012(2), 147-164. doi:10.1418/38783.

    Abstract

    This paper examines the role of morphological structure in the reduced pronunciation of morphologically complex words by discussing and re-analyzing data from the literature. Acoustic reduction refers to the phenomenon that, in spontaneous speech, phonemes may be shorter or absent. We review studies investigating effects of the repetition of a morpheme, of whether a segment plays a crucial role in the identification of its morpheme, and of a word's morphological decomposability. We conclude that these studies report either no effects of morphological structure or effects that are open to alternative interpretations. Our analysis also reveals the need for a uniform definition of morphological decomposability. Furthermore, we examine whether the reduction of segments in morphologically complex words correlates with these segments' contribution to the identification of the whole word, and discuss previous studies and new analyses supporting this hypothesis. We conclude that the data show no convincing evidence that morphological structure conditions reduction, which contrasts with the expectations of several models of speech production and of morphological processing (e.g., weaver++ and dual-route models). The data collected so far support psycholinguistic models which assume that all morphologically complex words are processed as complete units.
  • Schuppler, B., van Dommelen, W. A., Koreman, J., & Ernestus, M. (2012). How linguistic and probabilistic properties of a word affect the realization of its final /t/: Studies at the phonemic and sub-phonemic level. Journal of Phonetics, 40, 595-607. doi:10.1016/j.wocn.2012.05.004.

    Abstract

    This paper investigates the realization of word-final /t/ in conversational standard Dutch. First, based on a large number of word tokens (6747) annotated with broad phonetic transcription by an automatic transcription tool, we show that morphological properties of the words and their position in the utterance's syntactic structure play a role for the presence versus absence of their final /t/. We also replicate earlier findings on the role of predictability (word frequency and bigram frequency with the following word) and provide a detailed analysis of the role of segmental context. Second, we analyze the detailed acoustic properties of word-final /t/ on the basis of a smaller number of tokens (486) which were annotated manually. Our data show that word and bigram frequency as well as segmental context also predict the presence of sub-phonemic properties. The investigations presented in this paper extend research on the realization of /t/ in spontaneous speech and have potential consequences for psycholinguistic models of speech production and perception as well as for automatic speech recognition systems.
  • Torreira, F., & Ernestus, M. (2012). Weakening of intervocalic /s/ in the Nijmegen Corpus of Casual Spanish. Phonetica, 69, 124-148. doi:10.1159/000343635.
  • Van de Ven, M., Ernestus, M., & Schreuder, R. (2012). Predicting acoustically reduced words in spontaneous speech: The role of semantic/syntactic and acoustic cues in context. Laboratory Phonology, 3, 455-481. doi:10.1515/lp-2012-0020.

    Abstract

    In spontaneous speech, words may be realised shorter than in formal speech (e.g., English yesterday may be pronounced like [jɛʃeɩ]). Previous research has shown that context is required to understand highly reduced pronunciation variants. We investigated the extent to which listeners can predict low predictability reduced words on the basis of the semantic/syntactic and acoustic cues in their context. In four experiments, participants were presented with either the preceding context or the preceding and following context of reduced words, and either heard these fragments of conversational speech, or read their orthographic transcriptions. Participants were asked to predict the missing reduced word on the basis of the context alone, choosing from four plausible options. Participants made use of acoustic cues in the context, although casual speech typically has a high speech rate, and acoustic cues are much more unclear than in careful speech. Moreover, they relied on semantic/syntactic cues. Whenever there was a conflict between acoustic and semantic/syntactic contextual cues, measured as the word's probability given the surrounding words, listeners relied more heavily on acoustic cues. Further, context appeared generally insufficient to predict the reduced words, underpinning the significance of the acoustic characteristics of the reduced words themselves.
  • Viebahn, M. C., Ernestus, M., & McQueen, J. M. (2012). Co-occurrence of reduced word forms in natural speech. In Proceedings of INTERSPEECH 2012: 13th Annual Conference of the International Speech Communication Association (pp. 2019-2022).

    Abstract

    This paper presents a corpus study that investigates the co-occurrence of reduced word forms in natural speech. We extracted Dutch past participles from three different speech registers and investigated the influence of several predictor variables on the presence and duration of schwas in prefixes and /t/s in suffixes. Our results suggest that reduced word forms tend to co-occur even if we partial out the effect of speech rate. The implications of our findings for episodic and abstractionist models of lexical representation are discussed.
  • Ernestus, M. (2006). Statistically gradient generalizations for contrastive phonological features. The Linguistic Review, 23(3), 217-233. doi:10.1515/TLR.2006.008.

    Abstract

    In mainstream phonology, contrastive properties, like stem-final voicing, are simply listed in the lexicon. This article reviews experimental evidence that such contrastive properties may be predictable to some degree and that the relevant statistically gradient generalizations form an inherent part of the grammar. The evidence comes from the underlying voice specification of stem-final obstruents in Dutch. Contrary to received wisdom, this voice specification is partly predictable from the obstruent’s manner and place of articulation and from the phonological properties of the preceding segments. The degree of predictability, which depends on the exact contents of the lexicon, directs speakers’ guesses of underlying voice specifications. Moreover, existing words that disobey the generalizations are disadvantaged by being recognized and produced more slowly and less accurately, also under natural conditions.We discuss how these observations can be accounted for in two types of different approaches to grammar, Stochastic Optimality Theory and exemplar-based modeling.
  • Ernestus, M., & Baayen, R. H. (2006). The functionality of incomplete neutralization in Dutch: The case of past-tense formation. In L. Goldstein, D. Whalen, & C. Best (Eds.), Laboratory Phonology 8 (pp. 27-49). Berlin: Mouton de Gruyter.
  • Ernestus, M., Lahey, M., Verhees, F., & Baayen, R. H. (2006). Lexical frequency and voice assimilation. Journal of the Acoustical Society of America, 120(2), 1040-1051. doi:10.1121/1.2211548.

    Abstract

    Acoustic duration and degree of vowel reduction are known to correlate with a word’s frequency of occurrence. The present study broadens the research on the role of frequency in speech production to voice assimilation. The test case was regressive voice assimilation in Dutch. Clusters from a corpus of read speech were more often perceived as unassimilated in lower-frequency words and as either completely voiced regressive assimilation or, unexpectedly, as completely voiceless progressive assimilation in higher-frequency words. Frequency did not predict the voice classifications over and above important acoustic cues to voicing, suggesting that the frequency effects on the classifications were carried exclusively by the acoustic signal. The duration of the cluster and the period of glottal vibration during the cluster decreased while the duration of the release noises increased with frequency. This indicates that speakers reduce articulatory effort for higher-frequency words, with some acoustic cues signaling more voicing and others less voicing. A higher frequency leads not only to acoustic reduction but also to more assimilation.
  • Kuzla, C., Mitterer, H., Ernestus, M., & Cutler, A. (2006). Perceptual compensation for voice assimilation of German fricatives. In P. Warren, & I. Watson (Eds.), Proceedings of the 11th Australasian International Conference on Speech Science and Technology (pp. 394-399).

    Abstract

    In German, word-initial lax fricatives may be produced with substantially reduced glottal vibration after voiceless obstruents. This assimilation occurs more frequently and to a larger extent across prosodic word boundaries than across phrase boundaries. Assimilatory devoicing makes the fricatives more similar to their tense counterparts and could thus hinder word recognition. The present study investigates how listeners cope with assimilatory devoicing. Results of a cross-modal priming experiment indicate that listeners compensate for assimilation in appropriate contexts. Prosodic structure moderates compensation for assimilation: Compensation occurs especially after phrase boundaries, where devoiced fricatives are sufficiently long to be confused with their tense counterparts.
  • Kuzla, C., Ernestus, M., & Mitterer, H. (2006). Prosodic structure affects the production and perception of voice-assimilated German fricatives. In R. Hoffmann, & H. Mixdorff (Eds.), Speech prosody 2006. Dresden: TUD Press.

    Abstract

    Prosodic structure has long been known to constrain phonological processes [1]. More recently, it has also been recognized as a source of fine-grained phonetic variation of speech sounds. In particular, segments in domain-initial position undergo prosodic strengthening [2, 3], which also implies more resistance to coarticulation in higher prosodic domains [5]. The present study investigates the combined effects of prosodic strengthening and assimilatory devoicing on word-initial fricatives in German, the functional implication of both processes for cues to the fortis-lenis contrast, and the influence of prosodic structure on listeners’ compensation for assimilation. Results indicate that 1. Prosodic structure modulates duration and the degree of assimilatory devoicing, 2. Phonological contrasts are maintained by speakers, but differ in phonetic detail across prosodic domains, and 3. Compensation for assimilation in perception is moderated by prosodic structure and lexical constraints.
  • Kuzla, C., Mitterer, H., & Ernestus, M. (2006). Compensation for assimilatory devoicing and prosodic structure in German fricative perception. In Variation, detail and representation: 10th Conference on Laboratory Phonology (pp. 43-44).
  • Mitterer, H., & Ernestus, M. (2006). Listeners recover /t/s that speakers reduce: Evidence from /t/-lenition in Dutch. Journal of Phonetics, 34(1), 73-103. doi:10.1016/j.wocn.2005.03.003.

    Abstract

    In everyday speech, words may be reduced. Little is known about the consequences of such reductions for spoken word comprehension. This study investigated /t/-lenition in Dutch in two corpus studies and three perceptual experiments. The production studies revealed that /t/-lenition is most likely to occur after [s] and before bilabial consonants. The perception experiments showed that listeners take into account both phonological context, phonetic detail, and the lexical status of the form in the interpretation of codas that may or may not contain a lenited word-final /t/. These results speak against models of word recognition that make hard decisions on a prelexical level.
  • Pluymaekers, M., Ernestus, M., Baayen, R. H., & Booij, G. (2006). The role of morphology in fine phonetic detail: The case of Dutch -igheid. In Variation, detail and representation: 10th Conference on Laboratory Phonology (pp. 53-54).
  • Pluymaekers, M., Ernestus, M., & Baayen, R. H. (2006). Effects of word frequency on the acoustic durations of affixes. In Proceedings of Interspeech 2006 (pp. 953-956). Pittsburgh: ICSLP.

    Abstract

    This study investigates whether the acoustic durations of derivational affixes in Dutch are affected by the frequency of the word they occur in. In a word naming experiment, subjects were presented with a large number of words containing one of the affixes ge-, ver-, ont, or -lijk. Their responses were recorded on DAT tapes, and the durations of the affixes were measured using Automatic Speech Recognition technology. To investigate whether frequency also affected durations when speech rate was high, the presentation rate of the stimuli was varied. The results show that a higher frequency of the word as a whole led to shorter acoustic realizations for all affixes. Furthermore, affixes became shorter as the presentation rate of the stimuli increased. There was no interaction between word frequency and presentation rate, suggesting that the frequency effect also applies in situations in which the speed of articulation is very high.
  • Ten Bosch, L., Baayen, R. H., & Ernestus, M. (2006). On speech variation and word type differentiation by articulatory feature representations. In Proceedings of Interspeech 2006 (pp. 2230-2233).

    Abstract

    This paper describes ongoing research aiming at the description of variation in speech as represented by asynchronous articulatory features. We will first illustrate how distances in the articulatory feature space can be used for event detection along speech trajectories in this space. The temporal structure imposed by the cosine distance in articulatory feature space coincides to a large extent with the manual segmentation on phone level. The analysis also indicates that the articulatory feature representation provides better such alignments than the MFCC representation does. Secondly, we will present first results that indicate that articulatory features can be used to probe for acoustic differences in the onsets of Dutch singulars and plurals.
  • Wagner, A., Ernestus, M., & Cutler, A. (2006). Formant transitions in fricative identification: The role of native fricative inventory. Journal of the Acoustical Society of America, 120(4), 2267-2277. doi:10.1121/1.2335422.

    Abstract

    The distribution of energy across the noise spectrum provides the primary cues for the identification of a fricative. Formant transitions have been reported to play a role in identification of some fricatives, but the combined results so far are conflicting. We report five experiments testing the hypothesis that listeners differ in their use of formant transitions as a function of the presence of spectrally similar fricatives in their native language. Dutch, English, German, Polish, and Spanish native listeners performed phoneme monitoring experiments with pseudowords containing either coherent or misleading formant transitions for the fricatives / s / and / f /. Listeners of German and Dutch, both languages without spectrally similar fricatives, were not affected by the misleading formant transitions. Listeners of the remaining languages were misled by incorrect formant transitions. In an untimed labeling experiment both Dutch and Spanish listeners provided goodness ratings that revealed sensitivity to the acoustic manipulation. We conclude that all listeners may be sensitive to mismatching information at a low auditory level, but that they do not necessarily take full advantage of all available systematic acoustic variation when identifying phonemes. Formant transitions may be most useful for listeners of languages with spectrally similar fricatives.
  • Wurm, L. H., Ernestus, M., Schreuder, R., & Baayen, R. H. (2006). Dynamics of the auditory comprehension of prefixed words: Cohort entropies and conditional root uniqueness points. The Mental Lexicon, 1(1), 125-146.

    Abstract

    This auditory lexical decision study shows that cohort entropies, conditional root uniqueness points, and morphological family size all contribute to the dynamics of the auditory comprehension of prefixed words. Three entropy measures calculated for different positions in the stem of Dutch prefixed words revealed facilitation for higher entropies, except at the point of disambiguation, where we observed inhibition. Morphological family size was also facilitatory, but only for prefixed words in which the conditional root uniqueness point coincided with the conventional uniqueness point. For words with early conditional disambiguation, in contrast, only the morphologically related words that were onset-aligned with the target word facilitated lexical decision.

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