Ana Isabel Mata

Speaking style effects in the production of disfluencies

Abstract This work explores speaking style effects in the production of disfluencies. University lectures and map-task dialogues are analyzed in order to evaluate if the prosodic strategies used when uttering disfluencies vary across speaking styles. Our results show that the distribution of disfluency types is not arbitrary across lectures and dialogues. Moreover, although there is a statistically significant cross-style strategy of prosodic contrast marking (pitch and energy increases) between the region to repair and the repair of fluency, this strategy is displayed differently depending on the specific speech task. The overall patterns observed in the lectures, with regularities ascribed for speaker and disfluency types, do not hold with the same strength for the dialogues, due to underlying specificities of the communicative purposes. The tempo patterns found for both speech tasks also confirm their distinct behaviour, evidencing the more dynamic tempo characteristics of dialogues. In university lectures, prosodic cues are given to the listener both for the units inside disfluent regions and between these and the adjacent contexts. This suggests a stronger prosodic contrast marking of disfluency–fluency repair when compared to dialogues, as if teachers were monitoring the different regions – the introduction to a disfluency, the disfluency itself and the beginning of the repair – demarcating them in very contrastive ways.

Prosodic Phrasing: Machine and Human Evaluation

This paper describes a set of experiments aiming at the construction and evaluation of a new phrasing module for European Portuguese text-to-speech synthesis, using classification and regression trees learned from hand-labelled texts. Using the assessment criteria of matching boundary predictions against the corresponding labelled ones, the best solution achieves an overall performance of 91.9%, with 86.3% of correctly assigned breaks and 4.3% of false insertions. Although in absolute terms such scores may be considered surprisingly good given the size of the training set, the total number of exact matches at the sentence level is much lower (22%). This suggested a more formal experiment to test the acceptability of the predicted phrasing in the judgement of human evaluators. As the model was not trained on a labelled speech corpus but on hand-labelled texts, the reference phrasing needed also to be assessed. The evaluation experiment involved 90 participants who were asked to grade both the automatic and the reference phrasings, and also to express their opinion on where the breaks should be placed. As expected, the results showed a large variability among the subjects in their acceptance of a specific sentence partition, and criteria had to be defined to summarise the data from the different evaluators. With the adopted criteria, the performance of the automatic assignment procedure at the sentence level is better rated by human evaluators than by simple matching with the reference corpus (78% vs. 22%, respectively).

Stylistic variation in the intonation of European Portuguese teenagers and adults

Studies of emerging prosody from the word to the phrase, integrating various sources of evidence, are scarce, and our understanding of the pathways of prosodic development is still very limited. An investigation of emerging intonation and prosodic phrasing was undertaken on the basis of production data on intonation and duration patterns from the speech of two European Portuguese children between 1;00 and 2;04. The results show that both the development of intonation and phrasing were found to precede the onset of combinatorial speech, and to coincide in time with critical points in lexical development. Prosodic phrasing evolved in three steps, by the unfolding of key prosodic levels. Implications of these results are discussed in relation to early prosodic development across languages.

Analysis of interrogatives in different domains

The aim of this work is twofold: to quantify the distinct interrogative types in different domains for European Portuguese, and to discuss the weight of the linguistic features that best describe these structures, in order to model interrogatives in speech. We analyzed spoken dialogue, university lectures, and broadcast news corpora, and, for the sake of comparison, newspaper texts. The statistical analysis confirms that the percentage of the different types of interrogative is highly dependent on the nature of the corpus. Experiments on the automatic detection of interrogatives for European Portuguese, using only lexical cues, show results that are strongly correlated with the detection of a specific type of interrogatives (namely wh- questions). When acoustic and prosodic features (pitch, energy and duration) are added, yes/no and tag questions are then increasingly identified, showing the advantages of combining both lexical, acoustic and prosodic information.

Disfluencies and the perspective of prosodic fluency

This work explores prosodic cues of disfluent phenomena. We have conducted a perceptual experiment to test if listeners would rate all disfluencies as disfluent events or if some of them would be rated as fluent devices in specific prosodic contexts. Results pointed out significant differences (p < 0.05) between judgments of fluency vs. disfluency. Distinct prosodic properties of these events were also significant (p < 0.05) in their characterization as fluent devices. In an attempt to discriminate which linguistic features are more salient in the classification of disfluencies, we have also used CART techniques on a corpus of 3.5 hours of spontaneous and prepared non-scripted speech. CART results pointed out 2 splits: break indices and contour shape. The first split indicates that disfluent events uttered at breaks 3 and 4 are considered felicitous. The second one indicates that these events must have plateau or ascending contours to be considered as such; otherwise they are strongly penalized. The results obtained show that there are regular trends in the production of disfluencies, namely, prosodic phrasing and contour shape.

Adaptação acústico-prosódica entre falantes

This paper presents a global analysis of entrainment in map-task dialogues in European Portuguese, including 48 dialogues, between 24 speakers. Our main goal is to analyze the acoustic-prosodic similarities between speaker pairs, namely if there are global entrainment cues displayed in the dialogues, if entrainment is manifested in distinct sets of features shared amongst the speakers, if entrainment depends on the gender and role of the speaker (giver or follower), and if speakers tend to entrain more with specific interlocutors regardless of the role. Results show that globally speakers tend to be more similar to their partners than to their own speech in the majority of the analyzed features, a strong evidence for entrainment. Moreover, almost all the pairs of speakers display cues of global entrainment, even though in different degrees (speakers entrain but in distinct features). Additionally, the role and gender effects tend to be less striking than the specific interlocutor effect. Our results support the fact that all prosodic parameters are monitored by the speakers in our corpus, contrarily to studies for other languages, which indicate that the main cues are energy related.

Global analysis of entrainment in dialogues

This paper performs a global analysis of entrainment between dyads in map-task dialogues in European Portuguese (EP), including 48 dialogues, between 24 speakers. Our main goals focus on the acoustic-prosodic similarities between speakers, namely if there are global entrainment cues displayed in the dialogues, if there are degrees of entrainment manifested in distinct sets of features shared amongst the speakers, if entrainment depends on the role of the speaker as either giver or follower, and also if speakers tend to entrain more with specific pairs regardless of the role. Results show global entrainment in almost all the dyads, but the degrees of entrainment (stronger within the same gender), and the role effects tend to be less striking than the interlocutors’ effect. Globally, speakers tend to be more similar to their own speech in other dialogues than to their partners. However, speakers are also more similar to their interlocutors than to speakers with whom they never spoke.