Please use this identifier to cite or link to this item: http://hdl.handle.net/1893/21809
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dc.contributor.advisorDonaldson, David-
dc.contributor.advisorCorley, Martin-
dc.contributor.authorBouwsema, Jennifer A E-
dc.date.accessioned2015-05-28T10:12:59Z-
dc.date.issued2014-10-31-
dc.identifier.urihttp://hdl.handle.net/1893/21809-
dc.description.abstractDifficulties in speech production are often marked by disfluency; fillers, hesitations, prolongations, repetitions and repairs. In recent years a body of work has emerged that demonstrates that listeners are sensitive to disfluency, and that this affects their expectations for upcoming speech, as well as their attention to the speech stream. This thesis investigates the extent to which delay may be responsible for triggering these effects. The experiments reported in this thesis build on an Event Related Potential (ERP) paradigm developed by Corley et al., (2007), in which participants listened to sentences manipulated by both fluency and predictability. Corley et al. reported an attenuated N400 effect for words following disfluent ers, and interpreted this as indicating that the extent to which listeners made predictions was reduced following an er. In the current set of experiments, various noisy interruptions were added to Corley et al.,'s paradigm, time matched to the disfluent fillers. These manipulations allowed investigation of whether the same effects could be triggered by delay alone, in the absence of a cue indicating that the speaker was experiencing difficulty. The first experiment, which contrasted disfluent ers with artificial beeps, revealed a small but significant reduction in N400 effect amplitude for words affected by ers but not by beeps. The second experiment, in which ers were contrasted with speaker generated coughs, revealed no fluency effects on the N400 effect. A third experiment combined the designs of Experiments 1 and 2 to verify whether the difference between them could be characterised as a context effect; one potential explanation for the difference between the outcomes of Experiments 1 and 2 is that the interpretation of an er is affected by the surrounding stimuli. However, in Experiment 3, once again no effect of fluency on the magnitude of the N400 effect was found. Taken together, the results of these three studies lead to the question of whether er's attenuation effect on the N400 is robust. In a second part to each study, listeners took part in a surprise recognition memory test, comprising words which had been the critical words in the previous task intermixed with new words which had not appeared anywhere in the sentences previously heard. Participants were significantly more successful at recognising words which had been unpredictable in their contexts, and, importantly, for Experiments 1 and 2, were significantly more successful at recognising words which had featured in disfluent or interrupted sentences. There was no difference between the recognition rates of words which had been disfluent and those which were affected by a noisy interruption. Collard et al., (2008) demonstrated that disfluency could raise attention to the speech stream, and the finding that interrupted words are equally well remembered leads to the suggestion that any noisy interruption can raise attention. Overall, the finding of memory benefits in response to disfluency, in the absence of attenuated N400 effects leads to the suggestion that different elements of disfluencies may be responsible for triggering these effects. The studies in this thesis also extend previous work by being designed to yield enough trials in the memory test portion of each experiment to permit ERP analysis of the memory data. Whilst clear ERP memory effects remained elusive, important progress was made in that memory ERPs were generated from a disfluency paradigm, and this provided a testing ground on which to demonstrate the use of linear mixed-effects modelling as an alternative to ANOVA analysis for ERPs. Mixed-effects models allow the analysis of unbalanced datasets, such as those generated in many memory experiments. Additionally, we demonstrate the ability to include crossed random effects for subjects and items, and when this is applied to the ERPs from the listening section of Experiment 1, the effect of fluency on N400 amplitude is no longer significant. Taken together, the results from the studies reported in this thesis suggest that temporal delay or disruption in speech can trigger raised attention, but do not necessarily trigger changes in listeners' expectations.en_GB
dc.language.isoenen_GB
dc.publisherUniversity of Stirlingen_GB
dc.publisherUniversity of Edinburghen_GB
dc.subjectdisfluencyen_GB
dc.subjectEEGen_GB
dc.subjectdysfluencyen_GB
dc.subjectmemoryen_GB
dc.subjectmixed modelsen_GB
dc.subjectmixed effectsen_GB
dc.subjectN400en_GB
dc.subjectERPen_GB
dc.subject.lcshFluency (Language learning)en_GB
dc.subject.lcshAnalysis of varianceen_GB
dc.titleDisfluency as... er... delay: An investigation into the immediate and lasting consequences of disfluency and temporal delay using EEG and mixed-effects modellingen_GB
dc.typeThesis or Dissertationen_GB
dc.type.qualificationlevelDoctoralen_GB
dc.type.qualificationnameDoctor of Philosophyen_GB
dc.rights.embargodate2016-06-01-
dc.rights.embargoreasonPlease delay online public access while I consider whether to publish articles based on the data presented.en_GB
dc.contributor.funderSINAPSE: Scottish Imaging Network, A Platform for Scientific Excellenceen_GB
dc.author.emailjennybouwsema@gmail.comen_GB
dc.rights.embargoterms2016-07-01en_GB
dc.rights.embargoliftdate2016-07-01-
Appears in Collections:Psychology eTheses

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