The current dissertation represents one of the first systematic studies of the distribution of speech errors within supralexical prosodic units. Four experiments were conducted to gain insight into the specific role of these units in speech planning and production. The first experiment focused on errors in adult English. These were found to be systematically distributed within the highest-level supralexical prosodic unit, the Intonational Phrase (IP), providing evidence for its psychological reality. The specific distribution of errors--fewest in unit-initial position, with a gradual increase in errors across the unit--was interpreted to suggest that the IP functions as a planning domain: the unit is activated as a whole, and activation gradually decays with time leading to an increase in errors. The second experiment was motivated by the idea that a decrease in IP activation is best understood in the context of working memory processes. Children's speech was examined in preference to adult speech because it is less automatized and so likely more influenced by working memory. The findings were that children with better working memories produced shorter IPs and relatively more anticipatory errors than children with poorer working memories. The results provided further evidence for the role of IPs in planning. The third and fourth experiments extended the investigation to another language, Korean, and examined the role of a mid-level prosodic unit, the Accentual Phrase (AP), in planning and production. The results indicated the same pattern of error distribution in the Korean IP as in the English IP. In contrast, more errors occurred in AP-initial position than in the second half of the unit, and the elicited errors tended to preserve AP-internal structure. The results were interpreted to suggest that the AP provides a structural frame within which elements are slotted for production. Overall, the results are consistent with the idea that these units play a critical role in the planning and production process. The results also suggest that different units within the prosodic hierarchy function differently: the IP functions as a planning domain, and mid-level units (i.e., AP) provide the structure needed to accomplish serial ordering in speech. This dissertation includes previously published co-authored material.

Language production often requires speakers to convey information to a conversational partner about objects in their environment. According to Grice’s Maxim of Quantity (1975), speakers should provide only the precise amount of information needed to identify an object. However, it is frequently observed that speakers will include redundant adjectives in their referring expressions, rendering their descriptions overspecified. The majority of the research investigating overspecification has focused on how scene characteristics influence the likelihood of this behaviour. To date, less is known about the internal characteristics of the speaker that may play a role in the production of overspecified descriptions, and in referential communication more generally. The current experiment investigates the role of working memory in the generation of referential descriptions and examines how this interacts with manipulations of scene characteristics and cognitive load. Participants were asked to provide instructions to a confederate about which object to select from an array of either three or six unrelated objects while they simultaneously remembered a series of either zero, three, or five numbers. Participants also completed an operation span task to measure their individual working memory capacity (WMC). Results showed a main effect of array size for speech onset times, confirming that speakers are faster to initiate their speech when there are fewer objects in the display. Further, there was a significant three-way interaction between array size, cognitive load, and operation span scores, indicating that speakers with lower WMC are more likely to use redundant adjectives for three object arrays under low levels of load. Finally, there was a significant, negative correlation between speech rate and adjective use, indicating that speakers adjust their rate of speech depending on their choice of referring expression. The results of this research suggest a potential role for individual WMC in the production of overspecified descriptions. / Thesis / Master of Science (MSc) / Interactive communication often involves speakers relaying information to a conversational partner about objects in the environment, a phenomenon typically referred to as referential communication. A significant focus of previous research in this area is on how speakers chose to identify objects for a conversational partner. The focus of the current research is to examine the underlying cognitive mechanisms that support this behaviour. Participants were asked to communicate with a partner about objects on a computer screen while completing a secondary memory task. The findings of this research suggest that individual working memory capacity influences the amount of information speakers choose to include in their referential descriptions. Further, we show that including unnecessary information in object descriptions (i.e., referring to object attributes in the absence of contrastive objects) leads to a reduced speech rate, likely because of increased demands on speech planning.

Ce travail de thèse étudie la production de la parole à l'âge de 4 ans, en comparaison avec l'adulte, sous l'angle du contrôle moteur. Un intérêt particulier a été porté à deux indices : la variabilité liée à la répétition de voyelles isolées et la coarticulation anticipatoire intra et extra-syllabique dans le cadre de la production de séquences de type V1-C-V2. Des données acoustiques et articulatoires ont été enregistrées via l'échographie linguale et le dispositif HOCUS. Les données acoustiques ont été analysées pour 20 enfants et 10 adultes et les données articulatoires ont été analysées pour 6 de ces enfants et 2 de ces adultes. En accord avec de nombreuses études de la littérature, la variabilité liée à la répétition est plus importante chez les enfants que chez les adultes. Une forte anticipation de V2 dans la réalisation de V1 a été observée pour tous les adultes. Chez les enfants, cette anticipation n'est pas systématique, et lorsqu'elle est observée, elle est d'amplitude plus faible que chez les adultes. Ainsi, seulement 5 enfants parmi les 20 étudiés montrent des signes d'anticipation, majoritairement dans la dimension antéropostérieure, manifestée dans l'espace acoustique par la dimension F2. La coarticulation anticipatoire intra-syllabique semble également être d'amplitude plus faible chez les enfants. Enfin, les gestes de parole des enfants sont plus lents que ceux des adultes. Dans leur ensemble, ces résultats sont interprétés comme la preuve de l'immaturité du système moteur pour la production de la parole chez l'enfant, selon deux perspectives : des patrons moteurs insuffisamment stables pour la production de gestes vocaliques et un manque d'efficacité dans l'anticipation les gestes futurs lors de la production d'une séquence de sons de parole. Selon une perspective empruntée aux théories du contrôle moteur optimal, nous proposons que la coarticulation anticipatoire repose sur l'usage de modèles internes, représentations sensori-motrices du système moteur de la parole dans le système nerveux central, et que son amplitude reflète la maturation progressive de ces représentations sensori-motrices à mesure que la production de la parole se développe. / This thesis work investigates speech production in 4-year-old children, in comparison with adults, from a speech motor control perspective. It focuses on two indices: measures of token-to-token variability in the production of isolated vowels and on anticipatory intra and extra-syllabic coarticulation within V1-C-V2 sequences. Acoustic and articulatory data were recorded thanks to ultrasound tongue imaging within the HOCUS system. Acoustic data from 20 children and 10 adults have been analyzed. Ultrasound data have been analyzed from a subset of these participants: 6 children and 2 adults. In agreement with former studies, token-to-token variability was greater in children than in adults. Strong anticipation of V2 in V1 realization was found in all adults. In children, anticipation was not systematic, and when observed, it was of smaller amplitude than in adults. In more details, only 5 children among the 20 studied showed a small amount of anticipation, mainly along the antero-posterior dimension, manifested in the acoustic F2 dimension. Anticipatory intra-syllabic coarticulation also seems to be of smaller amplitude in children than in adults. Last, children's speech gestures are slower than those of adults. These results are interpreted as evidence for the immaturity of children's speech motor control from two perspectives: insufficiently stable motor control patterns for vowel production, and a lack of effectiveness in anticipating forthcoming gestures. In line with theories of optimal motor control, we assume that anticipatory coarticulation is based on the use of internal models, i.e. sensori-motor representations of the speech production apparatus in the central nervous system, and that the amplitude of anticipatory coarticulation reflects the increasing maturation of these sensori-motor representations as speech develops.

Conversation is the primary mode of language use. A key feature of conversation is turn-taking, during which interlocutors rapidly switch between speaker and listener roles without conscious effort. As previous neuroimaging studies have investigated language comprehension in isolated contexts, little is known regarding the neurocognitive bases of language use in reciprocal interaction. The present fMRI study investigates turn-taking, production, and comprehension processes, by utilizing existing conversational data between participants (N = 23) and a confederate outside the scanner. Turn initiations were associated with regions (the medial prefrontal cortex and the middle frontal gyrus) outside of the perisylvian core language network. Production and comprehension were both associated with core language regions in the temporal lobes, but activation in the left inferior frontal gyrus was mainly associated with production. Activation in the fusiform face area was linked to comprehension. The current findings suggest that (1) the coordination of speaker change is dependent on pragmatic processes that have been relatively overlooked in models of speech preparation, and (2) listeners are aided by their interlocutor's facial gestures when processing speech input during conversation. In addition, the results indicate that production and comprehension processes may differ (e.g., on the syntactic level), even in conversation. / Konversation är en central aspekt av språkanvändning. Något som kännetecknar konversation är turtagning, där samtalsdeltagare snabbt och utan ansträngning växlar mellan lyssnar- och talarroller. Eftersom tidigare neurolingvistiska studier huvudsakligen har undersökt språkförståelse i isolerade kontexter så är förståelsen för de underliggande neurokognitiva funktionerna som möjliggör mänsklig konversation fortfarande liten. Den här studien ämnade att undersöka vilka hjärnregioner som aktiveras under turtagning, språkproduktion och språkförståelse, genom att använda data från funktionell magnetresonanstomografi (fMRT), när deltagare (N = 23) ingick i samtal med en samtalspartner utanför skannern. Turinitieringar associerades med regioner (mediala prefrontala cortex och mellersta frontala gyrusen) utanför det klassiska språknätverket. Det här indikerar att koordinering av talarbyte involverar pragmatiska processer, vilka fått relativt lite uppmärksamhet i tidigare modeller för planering av språkproduktion. Produktion och förståelse aktiverade områden inom språknätverket, men aktivering i den inferiora frontala gyrusen var huvudsakligen associerad med produktion. En möjlig tolkning av det fyndet är att produktion och förståelse i konversation involverar distinkta processer på syntaktisk nivå. Aktivering i det fusiforma ansiktsområdet var huvudsakligen relaterad till förståelse, vilket indikerar att lyssnare använder information i deras samtalspartners ansiktsuttryck medan de tolkar ett yttrande.