Strength of linguistic text evidence: A fused forensic text comparison system

Compared to other forensic comparative sciences, studies of the efficacy of the likelihood ratio (LR) framework in forensic authorship analysis are lagging. An experiment is described concerning the estimation of strength of linguistic text evidence within that framework. The LRs were estimated by trialling three different procedures: one is based on the multivariate kernel density (MVKD) formula, with each group of messages being modelled as a vector of authorship attribution features; the other two involve N-grams based on word tokens and characters, respectively. The LRs that were separately estimated from the three different procedures are logistic-regression-fused to obtain a single LR for each author comparison. This study used predatory chatlog messages sampled from 115 authors. To see how the number of word tokens affects the performance of a forensic text comparison (FTC) system, token numbers used for modelling each group of messages were progressively increased: 500, 1000, 1500 and 2500 tokens. The performance of the FTC system is assessed using the log-likelihood-ratio cost (Cllr), which is a gradient metric for the quality of LRs, and the strength of the derived LRs is charted as Tippett plots. It is demonstrated in this study that (i) out of the three procedures, the MVKD procedure with authorship attribution features performed best in terms of Cllr, and that (ii) the fused system outperformed all three of the single procedures. When the token length is 1500, for example, the fused system achieved a Cllr value of 0.15. Some unrealistically strong LRs were observed in the results. Reasons for these are discussed, and a possible solution to the problem, namely the empirical lower and upper bound LR (ELUB) method is trialled and applied to the LRs of the best-achieving fusion system

Prosodic factors that affect the accentedness of L2 Japanese utterances: What matters most?

This study aims to identify which of two crucial prosodic factors has greatest impact on native speakers’ judgement of the accentedness of second language (L2) pronunciation. Prosodic features are already known to have more impact on the accentedness of L2 learners’ pronunciation than segmental features do. In this study, timing and pitch are looked at as major prosodic factors that affect native speakers’ accentedness judgement of L2 pronunciation. To examine the relative importance of timing and pitch, two types of speech samples—natural speech and prosody-modified speech—were used. In two experiments, native Japanese listeners assessed the accentedness of these stimuli and the results were compared. Both experiments obtained the same result: that timing is more important than pitch in improving the perceived naturalness of L2 Japanese speech

Text-dependent Forensic Voice Comparison: Likelihood Ratio Estimation with the Hidden Markov Model (HMM) and Gaussian Mixture Model – Universal Background Model (GMMUBM) Approaches

Among the more typical forensic voice comparison (FVC) approaches, the acoustic-phonetic statistical approach is suitable for text-dependent FVC, but it does not fully exploit available time-varying information of speech in its modelling. The automatic approach, on the other hand, essentially deals with text-independent cases, which means temporal information is not explicitly incorporated in the modelling. Text-dependent likelihood ratio (LR)-based FVC studies, in particular those that adopt the automatic approach, are few. This preliminary LR-based FVC study compares two statistical models, the Hidden Markov Model (HMM) and the Gaussian Mixture Model (GMM), for the calculation of forensic LRs using the same speech data. FVC experiments were carried out using different lengths of Japanese short words under a forensically realistic, but challenging condition: only two speech tokens for model training and LR estimation. Log-likelihood-ratio cost (Cllr) was used as the assessment metric. The study demonstrates that the HMM system constantly outperforms the GMM system in terms of average Cllr values. However, words longer than three mora are needed if the advantage of the HMM is to become evident. With a seven-mora word, for example, the HMM outperformed the GMM by a Cllr value of 0.073

The linguistic anatomy of individual differences in Japanese monologues: focusing on particles and interjections

This is a linguistic study on idiosyncrasy manifested through language use in Japanese monologues. For this purpose, we use speaker classification techniques as analytical tools. Focusing on Japanese particles, the subcategories of these particles, and interjections, we aim to find out to what extent Japanese speakers are idiosyncratic in selecting certain words above others in monologues. We are interested in how differently or similarly the individualising information of speakers is manifested between the subcategories of these particles, and also between particles and interjections. The genres of the monologues in this study vary from conference presentations on various topics covering humanities, social sciences, natural sciences and engineering to mock public speeches on a variety of general topics, such as “most pleasant memory,” “about your community,” etc. We demonstrate in this study that Japanese particles and interjections carry different degrees of individualising information. We also discuss what contributes to the identified differences between them.ANU College of Arts & Social Sciences, School of Language Studies; ANU College of Asia and the Pacific, School of Culture, History and Languag

What Constitutes "Good Pronunciation" from L2 Japanese Learners' and Native Speakers' Perspectives? A Perception Study

Native speakers of a language can tell whether a speaker is native or non-native just by hearing one word or phrase in the language. It is expected that L2 learners will develop the ability to detect ‘good pronunciation’ as they establish the prototy

An acoustic-phonetic descriptive analysis of Kagoshima Japanese tonal phenomena

This thesis presents a linguistic-phonetic description of the acoustic properties of the contrastive accentual patterns in Kagoshima Japanese. Kagoshima Japanese is one of the traditionally so-called two pattern varieties of Japanese. Different phonological analyses of the contrast are described in detail in order to situate the phonetic description. Data from four native speakers—two males and two females—are used, appropriately log z-score normalised to yield mean normalised FO curves necessary for linguistic-phonetic description. Normalisation procedures are discussed, justified and explained. The acoustic realisation of the Kagoshima Japanese contrast is specified on words from one to seven syllables in length, and a surface representation proposed within Autosegmental-Metrical theory. Some microprosodic aspects are also examined, especially in terms of the effect of the syllable-rhyme structure (i.e. vowel length, final nasal) on FO. In addition is examined what happens when accentual units are juxtaposed in three types of syntagms (noun phrase e.g. nagaka tamago; possessive phrase e.g. mago no kimono; simple sentence, e.g. sakana ga nigeru). Where appropriate, comparisons are drawn with Standard Japanese to highlight similarities and differences in tonality. It is shown that, like Standard Japanese, the Kagoshima Japanese accentual contrast is realised as ± falling pitch/FO, and also like SJ, the contrast is manifested globally, throughout the word. Microprosodically, it is shown that syllable-final nasals are associated with higher FO, not necessarily on the nasal itself, and that heavy syllables also evince a higher FO. Finally, two extrinsic allotones—level and falling—are demonstrated for one of the accentual types, depending on its rhyme constituents. As far as the juxtaposed data are concerned, it is shown that, unlike Standard Japanese, no deaccentuation is involved. Moreover, a differential effect is demonstrated, in terms of FO downstep, with respect to syntactic type: noun phrases behave differently from possessive phrases and simple sentences in showing no downstep. It is suggested that the magnitude of downstep in Kagoshima Japanese may be smaller than in Standard Japanese. It is proposed that the linguistic-phonetic representations derived in this thesis can be used not only to investigate within-language linguistic features (e.g. the Kagoshima Japanese accentual contrast), but also to compare Kagoshima with the corresponding linguistic-phonetic representations of other Japanese varieties

Authorship Verification based on the Likelihood Ratio of Grammar Models

Authorship Verification (AV) is the process of analyzing a set of documents to determine whether they were written by a specific author. This problem often arises in forensic scenarios, e.g., in cases where the documents in question constitute evidence for a crime. Existing state-of-the-art AV methods use computational solutions that are not supported by a plausible scientific explanation for their functioning and that are often difficult for analysts to interpret. To address this, we propose a method relying on calculating a quantity we call $\lambda_G$ (LambdaG): the ratio between the likelihood of a document given a model of the Grammar for the candidate author and the likelihood of the same document given a model of the Grammar for a reference population. These Grammar Models are estimated using $n$-gram language models that are trained solely on grammatical features. Despite not needing large amounts of data for training, LambdaG still outperforms other established AV methods with higher computational complexity, including a fine-tuned Siamese Transformer network. Our empirical evaluation based on four baseline methods applied to twelve datasets shows that LambdaG leads to better results in terms of both accuracy and AUC in eleven cases and in all twelve cases if considering only topic-agnostic methods. The algorithm is also highly robust to important variations in the genre of the reference population in many cross-genre comparisons. In addition to these properties, we demonstrate how LambdaG is easier to interpret than the current state-of-the-art. We argue that the advantage of LambdaG over other methods is due to fact that it is compatible with Cognitive Linguistic theories of language processing

Development of a high-resolution two-dimensional detector-based dose verification system for tumor-tracking irradiation in the CyberKnife system

We aim to evaluate the basic characteristics of SRS MapCHECK (SRSMC) for CyberKnife (CK) and establish a dose verification system using SRSMC for the tumor-tracking irradiation for CK. The field size and angular dependence of SRSMC were evaluated for basic characterization. The output factors (OPFs) and absolute doses measured by SRSMC were compared with those measured using microDiamond and microchamber detectors and those calculated by the treatment planning system (TPS). The angular dependence was evaluated by comparing the SRSMC with a microchamber. The tumor-tracking dose verification system consists of SRSMC and a moving platform. The doses measured using SRSMC were compared with the doses measured using a microchamber and radiochromic film. The OPFs and absolute doses of SRSMC were within ±3.0% error for almost all field sizes, and the angular dependence was within ±2.0% for all incidence angles. The absolute dose errors between SRSMC and TPS tended to increase when the field size was smaller than 10 mm. The absolute doses of the tumor-tracking irradiation measured using SRSMC and those measured using a microchamber agreed within 1.0%, and the gamma pass rates of SRSMC in comparison with those of the radiochromic film were greater than 95%. The basic characteristics of SRSMC for CK presented acceptable results for clinical use. The results of the tumor-tracking dose verification system realized using SRSMC were equivalent to those of conventional methods, and this system is expected to contribute toward improving the efficiency of quality control in many facilities

健常者における主観的身体垂直の再テスト法による信頼性と加齢による差異

The subjective postural vertical (SPV) reflects gravity perception when the eyes are closed. Changes in the SPV on both the frontal and sagittal planes occur in response to neurological disorders and aging; however, these changes on the diagonal plane are unclear. Here we examined test–retest reliability (n=16) of and age-related changes (n=38) in the SPVon the diagonal plane. Subjects sat on an electrical vertical board (EVB), which was used to measure the SPVon the diagonal plane. An experimenter controlled and moved the EVB seat at a constant speed on the diagonal plane and measured the seat’s tilt using a digital inclinometer when subjects verbally reported that they had reached a true vertical position. Measurement was performed for eight trials, and the mean (tilt direction) and standard deviation (variability) were calculated. To determine test–retest reliability, the same experimenter repeatedly measured the SPV 1 week later. To assess age-related changes, tilt direction and variability were compared between the young (n=20) and elderly (n=18) groups. Test–retest reliability on the right and left diagonal planes was 0.61 or more. Moreover, tilt direction on the right diagonal plane – but not on the left diagonal plane – indicated a significant diagonally backward deviation in the elderly group compared with that in the young group.Variability was significantly higher in the elderly group on both planes. SPV measurement on the diagonal plane was indicated, and age-related changes were identified. Thus, future studies should assess the potential clinical applications of SPV in neurological disorders.首都大学東京学位論文甲第966号副論