Multi‐speaker experimental designs: Methodological considerations

Research on language use has become increasingly interested in the multimodal and interactional aspects of language – theoretical models of dialogue, such as the Communication Accommodation Theory and the Interactive Alignment Model are examples of this. In addition, researchers have started to give more consideration to the relationship between physiological processes and language use. This article aims to contribute to the advancement in studies of physiological and/or multimodal language use in naturalistic settings. It does so by providing methodological recommendations for such multi-speaker experimental designs. It covers the topics of (a) speaker preparation and logistics, (b) experimental tasks and (c) data synchronisation and post-processing. The types of data that will be considered in further detail include audio and video, electroencephalography, respiratory data and electromagnetic articulography. This overview with recommendations is based on the answers to a questionnaire that was sent amongst the members of the Horizon 2020 research network ‘Conversational Brains’, several researchers in the field and interviews with three additional experts.H2020 Marie Skłodowska‐Curie Actions http://dx.doi.org/10.13039/100010665Peer Reviewe

Jaw and Order

It is well-accepted that the jaw plays an active role in influencing vowel height. The general aim of the current study is to further investigate the extent to which the jaw is active in producing consonantal distinctions, with specific focus on coronal consonants. Therefore, tongue tip and jaw positions are compared for the German coronal consonants Is, J, t, d, n, 1/, that is, consonants having the same active articulators (apical/laminal) but differing in manner of articulation. In order to test the stability of articulatory positions for each of these coronal consonants, a natural perturbation paradigm was introduced by recording two levels of vocal effort: comfortable, and loud without shouting. Tongue and jaw movements of five speakers of German were recorded by means of EMMA during /aCa/ sequences. By analyzing the tongue tip and jaw positions and their spatial variability we found that (1) the jaw's contribution to these consonants varies with manner of articulation, and (2) for all coronal consonants the positions are stable across loudness conditions except for those of the nasal. Results are discussed with respect to the tasks of the jaw, and the possible articulatory adjustments that may accompany louder speech

Interaction between Phrasal Structure and Vowel Tenseness in German: An Acoustic and Articulatory Study

Phrase-final lengthening affects the segments preceding a prosodic boundary. This prosodic variation is generally assumed to be independent of the phonemic identity. We refer to this as the ‘uniform lengthening hypothesis’ (ULH). However, in German, lax vowels do not undergo lengthening for word stress or shortening for increased speech rate, indicating that temporal properties might interact with phonemic identity. We test the ULH by comparing the effect of the boundary on acoustic and kinematic measures for tense and lax vowels and several coda consonants. We further examine if the boundary effect decreases with distance from the boundary. Ten native speakers of German were recorded by means of electromagnetic articulography (EMA) while reading sentences that contained six minimal pairs varying in vowel tenseness and boundary type. In line with the ULH, the results show that the acoustic durations of lax vowels are lengthened phrase-finally, similarly to tense vowels. We find that acoustic lengthening is stronger the closer the segments are to the boundary. Articulatory parameters of the closing movements toward the post-vocalic consonants are affected by both phrasal position and identity of the preceding vowel. The results are discussed with regard to the interaction between prosodic structure and vowel tenseness.Peer Reviewe

Do airstream mechanisms influence tongue movement paths?

Velar consonants often show an elliptical pattern of tongue movement in symmetrical vowel contexts, but the forces responsible for this remain unclear. We here consider the role of overpressure (increased intraoral air pressure) behind the constriction by examining how movement patterns are modified when speakers change from an egressive to ingressive airstream. Tongue movement and respiratory data were obtained from 3 speakers. The two airstream conditions were additionally combined with two levels of speech volume. The results showed consistent reductions in forward tongue movement during consonant closure in the ingressive conditions. Thus, overpressure behind the constriction may partly determine preferred movement patterns, but it cannot be the only influence since forward movement during closure is usually reduced but not eliminated in ingressive speech

What role does the palate play in speech motor control? Insights from tongue kinematics for German alveolar obstruents

By means of simultaneous EMMA and EPG recordings, we investigated tongue tip kinematics and tongue palate contact patterns for four German speakers in order to compare production strategies of alveolar stops with fricatives. For alveolar stops versus fricatives, two different control strategies were hypothesized: a target above the contact location for alveolar stops resulting in a collision of the tongue tip at the palate as opposed to a precise positioning of the tongue at the lateral margins at the palate for alveolar fricatives. Additionally, we suspected differences between stops and fricatives with respect to anterior and lateral palate contacts and their influence on tongue kinematics. Results of this study confirmed two different control strategies for alveolar stops and fricatives by means of significant differences in movement amplitude, velocity, and duration of the closing gesture, the amplitude of deceleration peaks, tongue tip movement during acoustically defined closure and constriction, and maximal anterior contact during closure. Additionally, results for speaker dependent mechanisms were related to the subject's coronal palatal shape

Do a Robot's Eyes Change a Human's Speech?

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Does a robot’s gaze aversion affect human gaze aversion?

Gaze cues serve an important role in facilitating human conversations and are generally considered to be one of the most important non-verbal cues. Gaze cues are used to manage turn-taking, coordinate joint attention, regulate intimacy, and signal cognitive effort. In particular, it is well established that gaze aversion is used in conversations to avoid prolonged periods of mutual gaze. Given the numerous functions of gaze cues, there has been extensive work on modelling these cues in social robots. Researchers have also tried to identify the impact of robot gaze on human participants. However, the influence of robot gaze behavior on human gaze behavior has been less explored. We conducted a within-subjects user study (N = 33) to verify if a robot’s gaze aversion influenced human gaze aversion behavior. Our results show that participants tend to avert their gaze more when the robot keeps staring at them as compared to when the robot exhibits well-timed gaze aversions. We interpret our findings in terms of intimacy regulation: humans try to compensate for the robot’s lack of gaze aversion.Peer Reviewe