Reduktion in natürlicher Sprache

Natural (conversational) speech, compared to cannonical speech, is earmarked by the tremendous amount of variation that often leads to a massive change in pronunciation. Despite many attempts to explain and theorize the variability in conversational speech, its unique characteristics have not played a significant role in linguistic modeling. One of the reasons for variation in natural speech lies in a tendency of speakers to reduce speech, which may drastically alter the phonetic shape of words. Despite the massive loss of information due to reduction, listeners are often able to understand conversational speech even in the presence of background noise. This dissertation investigates two reduction processes, namely regressive place assimilation across word boundaries, and massive reduction and provides novel data from the analyses of speech corpora combined with experimental results from perception studies to reach a better understanding of how humans handle natural speech. The successes and failures of two models dealing with data from natural speech are presented: The FUL-model (Featurally Underspecified Lexicon, Lahiri & Reetz, 2002), and X-MOD (an episodic model, Johnson, 1997). Based on different assumptions, both models make different predictions for the two types of reduction processes under investigation. This dissertation explores the nature and dynamics of these processes in speech production and discusses its consequences for speech perception. More specifically, data from analyses of running speech are presented investigating the amount of reduction that occurs in naturally spoken German. Concerning production, the corpus analysis of regressive place assimilation reveals that it is not an obligatory process. At the same time, there emerges a clear asymmetry: With only very few exceptions, only [coronal] segments undergo assimilation, [labial] and [dorsal] segments usually do not. Furthermore, there seem to be cases of complete neutralization where the underlying Place of Articulation feature has undergone complete assimilation to the Place of Articulation feature of the upcoming segment. Phonetic analyses further underpin these findings. Concerning deletions and massive reductions, the results clearly indicate that phonological rules in the classical generative tradition are not able to explain the reduction patterns attested in conversational speech. Overall, the analyses of deletion and massive reduction in natural speech did not exhibit clear-cut patterns. For a more in-depth examination of reduction factors, the case of final /t/ deletion is examined by means of a new corpus constructed for this purpose. The analysis of this corpus indicates that although phonological context plays an important role on the deletion of segments (i.e. /t/), this arises in the form of tendencies, not absolute conditions. This is true for other deletion processes, too. Concerning speech perception, a crucial part for both models under investigation (X-MOD and FUL) is how listeners handle reduced speech. Five experiments investigate the way reduced speech is perceived by human listeners. Results from two experiments show that regressive place assimilations can be treated as instances of complete neutralizations by German listeners. Concerning massively reduced words, the outcome of transcription and priming experiments suggest that such words are not acceptable candidates of the intended lexical items for listeners in the absence of their proper phrasal context. Overall, the abstractionist FUL-model is found to be superior in explaining the data. While at first sight, X-MOD deals with the production data more readily, FUL provides a better fit for the perception results. Another important finding concerns the role of phonology and phonetics in general. The results presented in this dissertation make a strong case for models, such as FUL, where phonology and phonetics operate at different levels of the mental lexicon, rather than being integrated into one. The findings suggest that phonetic variation is not part of the representation in the mental lexicon.Natürliche (spontane) Sprache in Dialogen zeichnet sich, im Vergleich zu kanonischer Sprache, vor allem durch das enorme Ausmaß an Variation aus. Diese kann oft dazu führen, dass Wörter in der Aussprache massiv verändert werden. Trotz einiger Bemühungen, Variabilität in natürlicher Sprache zu erklären und theoretisch zu fassen, haben die einzigartigen Merkmale natürlicher Sprache kaum Eingang in linguistische Modelle gefunden. Einer der Gründe, warum Variation in natürlicher Sprache zu beobachten ist, liegt in der Tendenz der Sprecher, Sprache zu reduzieren. Dies kann die phonetische Gestalt von Wörtern drastisch beeinflussen. Obwohl hierdurch massiv Information durch Reduktion verloren geht, sind Hörer oft in der Lage Spontansprache zu verstehen, sogar, wenn Hintergrundgeräusche dies erschweren. Diese Dissertation untersucht zwei Reduktionsprozesse: Regressive Assimilation des Artikulationsortes über Wortgrenzen hinweg und Massive Reduktion. Es werden neue Daten präsentiert, die durch die Analysen von Sprachkorpora gewonnen wurden. Außerdem stehen experimentelle Ergebnisse von Perzeptionsstudien im Mittelpunkt, die helfen sollen, besser zu verstehen, wie Menschen mit natürlicher Sprache umgehen. Die Dissertation zeigt die Erfolge und Probleme von zwei Modellen im Umgang mit Daten von natürlicher Sprache auf: Das FUL-Modell (Featurally Underspecified Lexicon , Lahiri & Reetz, 2002), und X-MOD (ein episodisches Modell, Johnson, 1997). Aufgrund unterschiedlicher Annahmen machen die zwei Modelle verschiedene Vorhersagen für die beiden Reduktionsprozesse, die in dieser Dissertation untersucht werden. Es werden Art und Auswirkungen der beiden Prozesse für Sprachproduktion untersucht und die Konsequenzen für das Sprachverstehen beleuchtet. Was die Sprachproduktion betrifft, so zeigt eine Korpusanalyse von natürlich gesprochenem Deutsch, dass der Reduktionsprozess regressive Assimilation des Artikulationsortes nicht obligatorisch statt findet. Gleichzeitig wird eine hervorstechende Asymmetrie deutlich: Abgesehen von einigen wenigen Ausnahmen werden ausschließlich [koronale] Segmente assimiliert, [labiale] und [dorsale] Segmente normalerweise nicht. Außerdem, so legen die Produktionsdaten nahe, gibt es Fälle, in denen die Assimilation des Artikulationsortes an den Artikulationsort des Folgesegmentes komplett ist, also eine vollständige Neutralisierung der Merkmalskontraste vom Sprecher vorgenommen wurde. Phonetische Analysen bestätigen dieses Resultat. Im Fall von Löschungen und massiven Reduktion demonstrieren die Ergebnisse eindeutig, dass phonologische Regeln – im klassischen generativen Sinne – nicht in der Lage sind, die Reduktionsmuster zu beschreiben, die in Spontansprache vorkommen. Alles in allem zeigen die Analysen von massiven Reduktionen und Löschungen keine eindeutigen Muster auf. Um einzelne Faktoren, die Reduktionen beeinflussen, genauer untersuchen zu können, wurde die Löschung von (Wort) finalem /t/ anhand eines neuen, für diesen Zweck kreierten Korpus durchgeführt. Die Analyse dieses Korpus unterstreicht, dass, obwohl phonologischer Kontext eine gewichtigen Einfluss darauf hat, ob Segmente (d.h. /t/) gelöscht werden, dieser Einfluss eher als Tendenz verstanden werden muss, nicht als absolute Bedingung. Dieses Resultat trifft auch auf andere Löschungsprozesse zu. Beide Modelle (X-MOD und FUL), die in dieser Dissertation untersucht werden, gehen im Kern der Frage nach, wie Hörer Sprache verstehen. Fünf Experimente untersuchen, wie reduzierte Sprache von menschlichen Hörern wahrgenommen wird. Ergebnisse von zwei Studien zeigen, dass Assimilationen von deutschen Hörern durchaus als komplett neutralisiert wahrgenommen werden. Was die Perzeption von massiv reduzierten Wörtern betrifft, belegen die Resultate von Transkriptionsstudien und Priming-Experimenten, dass solche Wörter nicht als Wortkandidaten für die korrekten lexikalischen Einträge akzeptiert werden, wenn sie ohne ihren Satz-Kontext dargeboten werden. Insgesamt ist das abstraktionistische FUL-Modell besser in der Lage, die Daten zu erklären, die in dieser Dissertation präsentiert werden. Auf den ersten Blick scheint X-MOD zwar etwas besser geeignet, die Produktionsdaten zu erklären, hauptsächlich jedoch, weil Variation als Grundannahme im Modell verankert ist. FUL ist klar überlegen, was die Perzeptionsseite betrifft. Ein weiteres wichtiges Ergebnis dieser Dissertation ist die Rolle, die Phonologie und Phonetik im Allgemeinen zugedacht werden kann. Die Resultate, die hier vorgestellt werden, liefern starke Argumente für Modelle – wie z.B. FUL – in denen Phonologie und Phonetik auf verschiedenen Ebenen des mentalen Lexikons aktiv sind und nicht in einem integriert sind. Die Befunde legen nahe, dass phonetische Variation nicht Teil der Repräsentation im mentalen Lexikon ist

An event-related potential investigation of the neural representations that support familiarity-based picture recognition

Most models of recognition memory assume that familiarity results from the matching of stimuli to the contents of memory. This matching process accumulates evidence that the stimulus was seen before, and when the evidence exceeds a criterion, a feeling of familiarity is experienced. Such models do not specify what constitutes evidence, and therefore offer limited insight into the specific attributes that make stimuli feel familiar. In two experiments, this dissertation examined the type of pictorial attributes that serve as evidence for familiarity-based picture recognition. Participants encoded briefly presented, masked pictures while event-related brain potentials (ERPs) were recorded. Of primary interest were ERPs for pictures that participants could not identify by name, as previous behavioral research suggests that such items are recognized on the basis of familiarity. Analysis of these encoding ERPs revealed that the global shape of subsequently recognized yet unidentified pictures was fully extracted during the picture\u27s brief presentation, but that their global object shapes were not successfully matched to object representations in memory (Exp 1 & 2). This result indicated that the memory trace for unidentified pictures contained limited conceptual information, and perceptual details that were abstract rather than detailed/episodic. ERPs recorded during retrieval revealed that the neural correlate of familiarity-based retrieval, the FN400, was present for unidentified pictures (Exp 1 & 2), and that the FN400 was more pronounced when participants were oriented toward processing perceptual, as opposed to conceptual, attributes of pictures during encoding (Exp 2). The behavioral measure of familiarity was consistent was consistent with this finding, which together implied that the largely perceptual representations in the pictorial memory trace were sufficient for later recognition of the unidentified picture, and that the pictures were more familiar when perceptual processing was greatest at encoding. The data presented in this dissertation indicate that familiarity-based picture recognition can be based on evidence that is largely perceptual and abstractly represented. The results are discussed within the context of perirhinal cortex models of familiarity, which suggest that picture familiarity is based on conjunctive features represented by the perirhinal cortex within the medial temporal lobe

Semantic structure of personal information

A sequential arrangement of processing stages is incorporated into most theoretical models of person recognition (e.g., Bruce and Young, 1986). Simple familiar/unfamiliar decisions are earliest, followed by access to semantic information, followed by naming. To date, the stage involved in semantic decisions has received least attention. Thus, relatively little is known about how we store personal semantic information. More research into this stage is necessary if we are to better understand the organisation of semantic memory for familiar people. The primary aim of this dissertation is to provide new evidence relating to the storage and retrieval of such information. The first line of enquiry attempts to discriminate between two influential models in this area (Burton et.al., 1990 and Bredart et. al., 1995), by using a new method involving semantic judgement tasks in the traditional semantic priming paradigm. In one model (Burton et. al., 1990), semantic information is stored in a single undifferentiated pool. In the other model (Bredart et. al., 1995) semantic information is clustered into separate pools. The two types of account make different predictions about certain patterns of priming during information retrieval. The experiments reported here fail to discriminate between the models. Later experiments identify the locus of the reported semantic priming effects and provide an explanation of these findings within a structural model of person recognition

A Representational-Hierarchical Account: A New Theory of False Memories

Past research has supported a representational-hierarchical theory of memory and perception that extends the ventral visual stream into the medial temporal lobe. In this account, representations are organized in a hierarchical manner, such that structures located further anterior in the brain contain complex representations of whole objects and areas further posterior in the visual cortex contain representations of simple features. When conjunctive representations are compromised, an individual must rely on simple-feature representations to complete mnemonic and perceptual tasks. However, these simple-feature representations are susceptible to feature-level interference, which can cause false recognition of novel objects. The goal of the present study was to explore the account’s third assumption: the effect of interference. Experiment 1 examined the effect of interference on neural representations during fMRI. Experiment 2 investigated the effect of different types of interference on a behavioral memory task with older adults thought to have impaired conjunctive representations. Although the results of the first experiment were inconclusive, the second experiment revealed that older adults’ recognition memory performance was shielded from semantic, but not perceptual, interference. The implications of this finding are discussed

The effect of familiarity on face adaptation

Face adaptation techniques have been used extensively to investigate how faces are processed. It has even been suggested that face adaptation is functional in calibrating the visual system to the diet of faces to which an observer is exposed. Yet most adaptation studies to date have used unfamiliar faces: few have used faces with real world familiarity. Familiar faces have more abstractive representations than unfamiliar faces. The experiments in this thesis therefore examined face adaptation for familiar faces. Chapters 2 and 3 explored the role of explicit recognition of familiar faces in producing face identity after-effects (FIAEs). Chapter 2 used composite faces (the top half of a celebrity's face paired with the bottom half of an unfamiliar face) as adaptors and showed that only recognised composites produced significant adaptation. In Chapter 3 the adaptors were cryptic faces (unfamiliar faces subtly transformed towards a celebrity's face) and faces of celebrity's siblings. Unrecognised cryptic and sibling faces produced FIAEs for their related celebrity, but only when adapting and testing on the same viewpoint. Adaptation only transferred across viewpoint when a face was explicitly recognised. Chapter 4 demonstrated that face adaptation could occur for ecologically valid, personally familiar stimuli, a necessary pre-requisite if adaptation is functional in calibrating face processing mechanisms. A video of a lecturer's face produced FIAEs equivalent to that produced by static images. Chapters 5 and 6 used a different type of after-effect, the face distortion after-effect (FDAE), to explore the stability of our representations for personally familiar faces, and showed that even representations of highly familiar faces can be affected by exposure to distorted faces. The work presented here shows that it is important to take facial familiarity into account when investigating face adaptation effects, as well as increasing our understanding of how familiarity affects the representations of faces

What working memory is for

Glenberg focuses on conceptualizations that change from moment to moment, yet he dismisses the concept of working memory (sect. 4.3), which offers an account of temporary storage and on-line cognition. This commentary questions whether Glenberg's account adequately caters for observations of consistent data patterns in temporary storage of verbal and visuospatial information in healthy adults and in brain-damaged patients with deficits in temporary retention.</jats:p

From Cue to Recall : The Temporal Dynamics of Long-Term Memory Retrieval

A fundamental function of long-term memory is the ability to retrieve a specific memory when encountering a retrieval cue. The purpose of this dissertation was to further our understanding of such cued recall by investigating the temporal dynamics from the presentation of the retrieval cue until the target memory is recalled. Retrieval cues are often related with several memories. When such a retrieval cue is presented, the associated memories will compete for retrieval and this retrieval competition needs to be handled in order to retrieve the sought after target memory. Study 1 and Study 2 investigated the temporal dynamics of such competitive semantic cued recall. Interestingly, previous research has shown that the ability to retrieve the currently relevant target memory comes with a cost, namely retrieval-induced forgetting of the competing memories. These studies also investigated the role of competitor activation and target retrieval in this forgetting phenomenon. Study 1 investigated the electrophysiological correlates of reactivation of competing currently irrelevant memories and the role of such competitor activation in retrieval-induced forgetting. Competitor activation was related to an FN400 event-related potential (ERP) effect and this effect predicted increased levels of retrieval-induced forgetting, indicating that this forgetting effect is dependent on competitor activation. Study 2 examined processes involved in target retrieval in a similar competitive semantic cued recall task. The main finding in this study was that attempts to retrieve the target memory were related to a late posterior negativity ERP effect. Another important finding was that behavioural and ERP measures of target retrieval were unrelated to retrieval-induced forgetting. Retrieval cues can sometimes elicit involuntary retrieval of unwanted memories. Such memory intrusions are a core symptom of post-traumatic stress disorder. Study 3 investigated the temporal dynamics of such memory intrusions. One of the key findings was that memory intrusions were related to a negative slow wave ERP effect possibly reflecting the activation of the intruding memory in working memory. Taken together the findings in the dissertation indicate that cued recall involves several cognitive processes ranging from early automatic memory reactivation to conscious processes such as working memory activation and recollection. The findings have implications for cognitive theories of memory and have relevance for several clinical conditions including depression and post-traumatic stress disorder

Exemplars as a least-committed alternative to dual-representations in learning and memory

Despite some notable counterexamples, the theoretical and empirical exchange between the fields of learning and memory is limited. In an attempt to promote further theoretical exchange, I explored how learning and memory may be conceptualized as distinct algorithms that operate on a the same representations of past experiences. I review representational and process assumptions in learning and memory, by the example of evaluative conditioning and false recognition, and identified important similarities in the theoretical debates. Based on my review, I identify global matching memory models and their exemplar representation as a promising candidate for a common representational substrate that satisfies the principle of least commitment. I then present two cases in which exemplar-based global matching models, which take characteristics of the stimulus material and context into account, suggest parsimonious explanations for empirical dissociations in evaluative conditioning and false recognition in long-term memory. These explanations suggest reinterpretations of findings that are commonly taken as evidence for dual-representation models. Finally, I report the same approach provides also provides a natural unitary account of false recognition in short-term memory, a finding which challenges the assumption that short-term memory is insulated from long-term memory. Taken together, this work illustrates the broad explanatory scope and the integrative and yet parsimonious potential of exemplar-based global matching models

Neurocognitive Modulations of Lexical Access during Speech Production in Social and Semantic Context

Der Sprechakt teilt sich in zwei Vorgänge: Zunächst muss das richtige Wort aus dem mentalen Lexikon abgerufen werden und anschließend wird es in der Kommunikation verwendet. Zur Erforschung des ersteren Vorgangs werden oft Ein-Personen-Studien verwendet, in denen durch Beobachten der Reaktion auf Stimuli (z. B. Bilder) die Mikrostruktur des lexikalisch- semantischen Systems beleuchtet wird. Für die Anwendung von Sprache in der Kommunikation hingegen nutzt man Partnerexperimente, um die Koordination zwischen den Gesprächspartnern zu beobachten und zu ergründen, wie sich gegenseitiges Verstehen und biografisches Wissen darauf auswirken. Wenig erforscht ist aber, wie ein von einem Gesprächspartner eingebrachter Bedeutungskontext die traditionell in Ein-Personen-Studien untersuchten lexikalisch-semantischen Effekte beeinflusst. Im Rahmen meiner Dissertation möchte ich die Lücke zwischen den beiden Forschungsansätzen schließen, indem ich einen kommunikativen Kontext in etablierte Paradigmen der Bildbenennung integriere. Hierzu betrachte ich zunächst klassische semantische Kontexteffekte, die durch nähere oder entferntere kategorische Relationen zwischen Begriffen hervorgerufen werden (Studie 1), um anschließend lose thematische Beziehungen zu untersuchen, die mit alltäglichen Ereignissen verbunden sind (Studie 2 & Studie 3). Um die hochgradig verflochtenen Ebenen der lexikalischen und semantischen Verarbeitung voneinander zu trennen, habe ich ereigniskorrelierte Hirnpotentiale (ERPs) eingesetzt, um die elektrophysiologischen Signaturen des konzeptuellen Primings und der lexikalischen Auswahl zu verfolgen. Die vorliegende Arbeit liefert sowohl theoretische als auch praktische Beiträge. Erstens stützen unsere Ergebnisse die theoretischen Annahmen, dass sich semantisches Priming und lexikalische Interferenz vorübergehend überschneiden und gemeinsam das Benennungsverhalten in einem Trade-off beeinflussen. Auch die Gegenwart eines Kommunikationspartners kann Auswirkungen auf dieses Zusammenspiel haben. Zweitens ergänzen diese Ergebnisse die aktuelle Literatur zu verschiedenen Arten von semantischen Beziehungen, wie z. B. Nulleffekte für entfernte Beziehungen und Kontexteffekte, die systematisch mit der Stärke der Verwandtschaft zunehmen. Und schließlich bietet unser neuartiges Design eines kommunikativen Kontextes ein praktisches Instrument, um die Lücke zwischen Ein-Personen-Studien und Kommunikationsstudien zu schließen. Alles in allem tragen diese Ergebnisse zu einem besseren Verständnis der neuronalen Mechanismen unseres Sprachproduktionssystems bei, das in der Lage ist, sich flexibel sowohl an sprachliche als auch an soziale Kontexte anzupassen.Speaking could be divided into two processes: first, the correct word must be retrieved from the mental lexicon, and then it is used in communication. To study the former process, single-person studies are often used, in which the microstructure of the lexical-semantic system is illuminated by observing reaction times to name stimuli (e.g., pictures). For the language use in communication, on the other hand, partner experiments are used to observe coordination between interlocutors and to explore how mutual understanding and biographical knowledge affect it. However, how a meaningful context brought by an interlocutor influences the established lexical-semantic effects from single-person studies remains underexplored. Within the scope of my dissertation, I aim to bridge the gap between these two research approaches by integrating a communicative context into well-established picture naming paradigms. To this end, I first investigate classic semantic context effects induced by close or distant categorical relations (Study 1), and then examine loose thematic relations associated with everyday events (Study 2 & Study 3). To separate the highly intertwined strata of lexical and semantic processing, I used event-related brain potentials (ERPs) to track the electrophysiological signatures of conceptual priming and lexical selection. The present work makes both theoretical and practical contributions. First, our results support the theoretical assumptions that semantic priming and lexical interference temporarily overlap, and jointly modulate naming behavior in a trade-off. Such interplay may be greatly influenced by the presence of a communicating partner. Second, these findings add to the current literature on different types of semantic relations, such as null effects for distant relations and context effects that systematically increase with the strength of relatedness. Finally, our novel design of a communicative context provides a practical tool to bridge the gap between single-person studies and communication studies. All in all, these findings advance our understanding of the neural mechanisms of our speech production system, which is capable of flexibly adapting to both linguistic and social contexts

The role of phonology in visual word recognition: evidence from Chinese

Posters - Letter/Word Processing V: abstract no. 5024The hypothesis of bidirectional coupling of orthography and phonology predicts that phonology plays a role in visual word recognition, as observed in the effects of feedforward and feedback spelling to sound consistency on lexical decision. However, because orthography and phonology are closely related in alphabetic languages (homophones in alphabetic languages are usually orthographically similar), it is difficult to exclude an influence of orthography on phonological effects in visual word recognition. Chinese languages contain many written homophones that are orthographically dissimilar, allowing a test of the claim that phonological effects can be independent of orthographic similarity. We report a study of visual word recognition in Chinese based on a mega-analysis of lexical decision performance with 500 characters. The results from multiple regression analyses, after controlling for orthographic frequency, stroke number, and radical frequency, showed main effects of feedforward and feedback consistency, as well as interactions between these variables and phonological frequency and number of homophones. Implications of these results for resonance models of visual word recognition are discussed.postprin