Acoustic Properties Predict Perception of Unfamiliar Dutch Vowels by Adult Australian English and Peruvian Spanish Listeners

Discrimination of Second Language Vowel Contrasts and the Role of Phonological Short-Term Memory and Nonverbal Intelligence

Although extensive research has focused on the perceptual abilities of second language (L2) learners, a significant gap persists in understanding how cognitive functions like phonological short-term memory (PSTM) and nonverbal intelligence (IQ) impact L2 speech perception. This study sets out to investigate the discrimination of L2 English monophthongal vowel contrasts and to assess the effect of PSTM and nonverbal IQ on L2 speech perception. The participants consisted of adult monolingually-raised Greek speakers, who completed an AX discrimination test, a digit span test, and a nonverbal intelligence test. A control group of English speakers also completed the AX test. Data were analyzed using Bayesian regression models. The results revealed that Greek speakers exhibited below chance discrimination for the majority of L2 vowel contrasts, consistently underperforming in comparison to the control group. Intriguingly, the study did not provide substantial evidence in favor of more accurate discrimination of L2 contrasts by Greek participants with high PSTM compared to those with low PSTM. However, the study yielded compelling evidence indicating that Greek participants with higher IQ demonstrated superior accuracy in discriminating most L2 contrasts compared to their lower IQ counterparts. The limited influence of PSTM on speech perception suggests the need for further exploration, considering the potential impact of test methodologies and the intricate interplay of other confounding factors. Furthermore, the study uncovers a noteworthy relationship between nonverbal IQ and L2 speech perception, likely linked with the association of high IQ with enhanced attentional capacities, information processing abilities, and learning skills-all of which are pivotal for accurate speech perception.

Perception of Dutch vowels by Cypriot Greek listeners: To what extent can listeners' patterns be predicted by acoustic and perceptual similarity?

There have been numerous studies investigating the perception of non-native sounds by listeners with different first language (L1) backgrounds. However, research needs to expand to under-researched languages and incorporate predictions conducted under the assumptions of new speech models. This study aimed to investigate the perception of Dutch vowels by Cypriot Greek adult listeners and test the predictions of cross-linguistic acoustic and perceptual similarity. The predictions of acoustic similarity were formed using a machine-learning algorithm. Listeners completed a classification test, which served as the baseline for developing the predictions of perceptual similarity by employing the framework of the Universal Perceptual Model (UPM), and an AXB discrimination test; the latter allowed the evaluation of both acoustic and perceptual predictions. The findings indicated that listeners classified each non-native vowel as one or more L1 vowels, while the discrimination accuracy over the non-native contrasts was moderate. In addition, cross-linguistic acoustic similarity predicted to a large extent the classification of non-native sounds in terms of L1 categories and both the acoustic and perceptual similarity predicted the discrimination accuracy of all contrasts. Being in line with prior findings, these findings demonstrate that acoustic and perceptual cues are reliable predictors of non-native contrast discrimination and that the UPM model can make accurate estimations for the discrimination patterns of non-native listeners.

Explaining L2 Lexical Learning in Multiple Scenarios: Cross-Situational Word Learning in L1 Mandarin L2 English Speakers

Adults commonly struggle with perceiving and recognizing the sounds and words of a second language (L2), especially when the L2 sounds do not have a counterpart in the learner's first language (L1). We examined how L1 Mandarin L2 English speakers learned pseudo English words within a cross-situational word learning (CSWL) task previously presented to monolingual English and bilingual Mandarin-English speakers. CSWL is ambiguous because participants are not provided with direct mappings of words and object referents. Rather, learners discern word-object correspondences through tracking multiple co-occurrences across learning trials. The monolinguals and bilinguals tested in previous studies showed lower performance for pseudo words that formed vowel minimal pairs (e.g., /dit/-/dɪt/) than pseudo word which formed consonant minimal pairs (e.g., /bɔn/-/pɔn/) or non-minimal pairs which differed in all segments (e.g., /bɔn/-/dit/). In contrast, L1 Mandarin L2 English listeners struggled to learn all word pairs. We explain this seemingly contradicting finding by considering the multiplicity of acoustic cues in the stimuli presented to all participant groups. Stimuli were produced in infant-directed-speech (IDS) in order to compare performance by children and adults and because previous research had shown that IDS enhances L1 and L2 acquisition. We propose that the suprasegmental pitch variation in the vowels typical of IDS stimuli might be perceived as lexical tone distinctions for tonal language speakers who cannot fully inhibit their L1 activation, resulting in high lexical competition and diminished learning during an ambiguous word learning task. Our results are in line with the Second Language Linguistic Perception (L2LP) model which proposes that fine-grained acoustic information from multiple sources and the ability to switch between language modes affects non-native phonetic and lexical development.

The Acquisition of /ɪ/-/iː/ Is Challenging: Perceptual and Production Evidence from Cypriot Greek Speakers of English

This study aims to investigate the perception and production of the English /ɪ/-/iː/ vowel contrast by Cypriot Greek speakers of English as a second language (L2). The participants completed a classification test in which they classified the L2 vowels in terms of their first language (L1) categories, a discrimination test in which they distinguished the members of the vowel contrast, and a production test in which they produced the target vowels. The results showed that they classified both L2 /ɪ/-/iː/ mostly in terms of L1 /i/, which denotes the formation of a completely overlapping contrast according to the theoretical framework of the Universal Perceptual Model (UPM), and that they could hardly distinguish the vowel pair. In addition, their productions deviated in most acoustic parameters from the corresponding productions of English controls. The findings suggest that /ɪ/-/iː/ may carry a universal marker of difficulty for speakers with L1s that do not possess this contrast. This distinction is difficult even for experienced L2 speakers probably because they had never been exposed to naturalistic L2 stimuli and they do not use the L2 that much in their daily life. Finally, the study verifies UPM's predictions about the discriminability of the contrast and extends the model's implications to speech production; when an L2 vowel contrast is perceived as completely overlapping, speakers activate a (near-) unified interlinguistic exemplar in their vowel space, which represents both L2 vowels.

How expertise and language familiarity influence perception of speech of people with Parkinson's disease

Parkinson's disease (PD) is a progressive neurological disorder characterized by several motor and non-motor manifestations. PD frequently leads to hypokinetic dysarthria, which affects speech production and often has a detrimental impact on everyday communication. Among the typical manifestations of hypokinetic dysarthria, speech and language therapists (SLTs) identify prosody as the most affected cluster of speech characteristics. However, less is known about how untrained listeners perceive PD speech and how affected prosody influences their assessments of speech. This study explores the perception of sentence type intonation and healthiness of PD speech by listeners with different levels of familiarity with speech disorders in Dutch. We investigated assessments and classification accuracy differences between Dutch-speaking SLTs (n = 18) and Dutch/non-Dutch speaking untrained listeners (n = 27 and n = 124, respectively). We collected speech data from 30 Dutch speakers diagnosed with PD and 30 Dutch healthy controls. The stimuli set consisted of short phrases from spontaneous and read speech and of phrases produced with different sentence type intonation. Listeners participated in an online experiment targeting classification of sentence type intonation and perceived healthiness of speech. Results indicate that both familiarity with speech disorders and with speakers' language are significant and have different effects depending on the task type, as different listener groups demonstrate different classification accuracy. There is evidence that untrained Dutch listeners classify PD speech as unhealthy more accurately than both trained Dutch and untrained non-Dutch listeners, while trained Dutch listeners outperform the other two groups in sentence type classification.

The Role of Acoustic Similarity and Non-Native Categorisation in Predicting Non-Native Discrimination: Brazilian Portuguese Vowels by English vs. Spanish Listeners

This study tests whether Australian English (AusE) and European Spanish (ES) listeners differ in their categorisation and discrimination of Brazilian Portuguese (BP) vowels. In particular, we investigate two theoretically relevant measures of vowel category overlap (acoustic vs. perceptual categorisation) as predictors of non-native discrimination difficulty. We also investigate whether the individual listener’s own native vowel productions predict non-native vowel perception better than group averages. The results showed comparable performance for AusE and ES participants in their perception of the BP vowels. In particular, discrimination patterns were largely dependent on contrast-specific learning scenarios, which were similar across AusE and ES. We also found that acoustic similarity between individuals’ own native productions and the BP stimuli were largely consistent with the participants’ patterns of non-native categorisation. Furthermore, the results indicated that both acoustic and perceptual overlap successfully predict discrimination performance. However, accuracy in discrimination was better explained by perceptual similarity for ES listeners and by acoustic similarity for AusE listeners. Interestingly, we also found that for ES listeners, the group averages explained discrimination accuracy better than predictions based on individual production data, but that the AusE group showed no difference.

Toward a new model for speech perception: the Universal Perceptual Model (UPM) of second language

Several speech models have been formed in the past aiming to predict the abilities of nonnative listeners or learners in perceiving and producing speech sounds. The present paper proposes a new model for speech perception, the Universal Perceptual Model of Second Language (henceforth, UPM). UPM assumes that second language phone acquisition is strongly affected by the speakers' native language but still the window of phone learning is open due to the universality of speech sounds. Also, it supports that second language phones are initially activated as disoriented phonetic units. In this paper, we provide some initial insights into the predictability of the model. UPM uses degrees of overlap and chance criteria to form its predictions. We recruited Cypriot Greek novice learners of Italian who participated in two psychoacoustic tasks in which they classified and discriminated Italian vowels, respectively. The findings demonstrated that the degree of overlap between two nonnative phones may be a good predictor of the speakers' discrimination accuracy over these phones. UPM might be a useful model which aims to better explain speech perception mechanisms and patterns of speech acquisition.

Indexical and linguistic processing by 12-month-olds: Discrimination of speaker, accent and vowel differences

Infants preferentially discriminate between speech tokens that cross native category boundaries prior to acquiring a large receptive vocabulary, implying a major role for unsupervised distributional learning strategies in phoneme acquisition in the first year of life. Multiple sources of between-speaker variability contribute to children's language input and thus complicate the problem of distributional learning. Adults resolve this type of indexical variability by adjusting their speech processing for individual speakers. For infants to handle indexical variation in the same way, they must be sensitive to both linguistic and indexical cues. To assess infants' sensitivity to and relative weighting of indexical and linguistic cues, we familiarized 12-month-old infants to tokens of a vowel produced by one speaker, and tested their listening preference to trials containing a vowel category change produced by the same speaker (linguistic information), and the same vowel category produced by another speaker of the same or a different accent (indexical information). Infants noticed linguistic and indexical differences, suggesting that both are salient in infant speech processing. Future research should explore how infants weight these cues in a distributional learning context that contains both phonetic and indexical variation.