Multi-parametric analysis of speech timing in inter-talker identical twin pairs and cross-pair comparisons: Some forensic implications.

Julio Cesar Cavalcanti,Plinio A Barbosa,Anders Eriksson

doi:10.1371/journal.pone.0262800

Julio Cesar Cavalcanti, Plinio A Barbosa + Show 1 more

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https://doi.org/10.1371/journal.pone.0262800

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Journal: PloS one	Publication Date: Jan 21, 2022
Citations: 2	License type: CC BY 4.0

Affiliation: Stockholm University, Universidade Estadual de Campinas

Abstract

The purpose of this study was to assess the speaker-discriminatory potential of a set of speech timing parameters while probing their suitability for forensic speaker comparison applications. The recordings comprised of spontaneous dialogues between twin pairs through mobile phones while being directly recorded with professional headset microphones. Speaker comparisons were performed with twins speakers engaged in a dialogue (i.e., intra-twin pairs) and among all subjects (i.e., cross-twin pairs). The participants were 20 Brazilian Portuguese speakers, ten male identical twin pairs from the same dialectal area. A set of 11 speech timing parameters was extracted and analyzed, including speech rate, articulation rate, syllable duration (V-V unit), vowel duration, and pause duration. Three system performance estimates were considered for assessing the suitability of the parameters for speaker comparison purposes, namely global Cllr, EER, and AUC values. These were interpreted while also taking into consideration the analysis of effect sizes. Overall, speech rate and articulation rate were found the most reliable parameters, displaying the largest effect sizes for the factor “speaker” and the best system performance outcomes, namely lowest Cllr, EER, and highest AUC values. Conversely, smaller effect sizes were found for the other parameters, which is compatible with a lower explanatory potential of the speaker identity on the duration of such units and a possibly higher linguistic control regarding their temporal variation. In addition, there was a tendency for speech timing estimates based on larger temporal intervals to present larger effect sizes and better speaker-discriminatory performance. Finally, identical twin pairs were found remarkably similar in their speech temporal patterns at the macro and micro levels while engaging in a dialogue, resulting in poor system discriminatory performance. Possible underlying factors for such a striking convergence in identical twins’ speech timing patterns are presented and discussed.

Highlights

The present study set out to assess the speaker-discriminatory potential of a set of speech timing parameters in comparisons performed between identical twin pairs and in cross-pair comparisons
Apart from widely acknowledged general linguistic temporal patterns, how do individuals vary in speech timing measures when speaking in the same language and dialect? Can such a variation, within limits imposed by the production system, be regarded as speaker-discriminatory? what are the effects of reducing common sources of inter-speaker variation on speech temporal patterns? The present study represents an attempt at addressing such questions with special consideration to spontaneous speech materials
The effects of speaker/data sampling on Equal Error Rate (EER) and mostly on consistency: the Log-likelihood-ratiocost function (Cllr) values must be considered in future developments of the present study as to obtain relevant information on system stability regarding the parameters assessed and the level of uncertainty concerning the LR computation, cf. [68, 69]

Summary

Introduction

The present study set out to assess the speaker-discriminatory potential of a set of speech timing parameters in comparisons performed between identical twin pairs (while engaging in dialogue) and in cross-pair comparisons. The primary motivation for including the comparison of identical twins in the present study lies in the fact that such individuals represent an extrapolation of the highest possible similarity between subjects, both from a physical and sociolinguistic point of view, allowing the assessment and understanding of inter-subject variation levels. Genetically identical twins have been suggested as almost entirely correlated in their gray matter distribution, including areas related to language cortices, as observed by [2] with brain imaging. Another important observation is that identical twins raised together were exposed to very similar stimuli during their language acquisition and development, which may unquestionably impact their linguistic patterns. Some methodological aspects are revisited and developed in the following.

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