Linguistic processing of accented speech across the lifespan

I know how you'll say it: evidence of speaker-specific speech prediction

Most models of language comprehension assume that the linguistic system is able to pre-activate phonological information. However, the evidence for phonological prediction is mixed and controversial. In this study, we implement a paradigm that capitalizes on the fact that foreign speakers usually make phonological errors. We investigate whether speaker identity (native vs. foreign) is used to make specific phonological predictions. Fifty-two participants were recruited to read sentence frames followed by a last spoken word which was uttered by either a native or a foreign speaker. They were required to perform a lexical decision on the last spoken word, which could be either semantically predictable or not. Speaker identity (native vs. foreign) may or may not be cued by the face of the speaker. We observed that the face cue is effective in speeding up the lexical decision when the word is predictable, but it is not effective when the word is not predictable. This result shows that speech prediction takes into account the phonological variability between speakers, suggesting that it is possible to pre-activate in a detailed and specific way the phonological representation of a predictable word.

Navigating accent variability: 24-month-olds recognize known words spoken in an unfamiliar accent but require additional support to learn new words

As infants learn their native languages, they must also learn to contend with variability across speakers of those languages. Here, we examine 24-month-olds' ability to process speech in an unfamiliar accent. We demonstrate that 24-month-olds successfully identify the referents of known words in unfamiliar-accented speech but cannot use known words alone to infer new word meanings. However, when the novel word occurs in a supportive referential context, with the target referent visually available, 24-month-olds successfully learn new word-referent mappings. Thus, 24-month-olds recognize and learn words in unfamiliar accents, but unfamiliar-accented speech may pose challenges for more sophisticated language processing strategies.

Preschoolers benefit from sentential context in familiar- and unfamiliar-accented speech

To learn the meaning of a new word, or to recognize the meaning of a known one, both children and adults benefit from surrounding words, or the sentential context. Most of the evidence from children is based on their accuracy and efficiency when listening to speech in their familiar native accent: they successfully use the words they know to identify other words' referents. Here, we assess how accurately and efficiently 4-year-old children use sentential context to identify referents of known and novel nouns in unfamiliar-accented speech, as compared to familiar-accented speech. In a looking-while-listening task, children showed considerable success in processing unfamiliar-accented speech. Children robustly mapped known nouns produced in an unfamiliar accent to their target referents rather than novel competitors, and they used informative surrounding verbs (e.g., "You can eat the dax") to identify the referents of both known and novel nouns-although there was a processing cost for unfamiliar-accented speech in some cases. This demonstrates that 4-year-olds successfully and rapidly process unfamiliar-accented speech by recruiting the same strategies available to them in familiar-accented speech, revealing impressive flexibility in word recognition and word learning across diverse linguistic environments. RESEARCH HIGHLIGHTS: We examined 4-year-old children's accuracy and processing efficiency in comprehending known and novel nouns embedded in sentences produced in familiar-accented or unfamiliar-accented speech. Children showed limited processing costs for unfamiliar-accented speech and mapped known words to their referents even when these were produced in unfamiliar-accented speech. Children used known verbs to predict the referents of upcoming nouns in both familiar- and unfamiliar-accented speech, but processing costs were evident for unfamiliar-accented speech. Thus, the strategies that support children's word comprehension and word learning in familiar-accented speech are available to them in unfamiliar accents as well.

Category Flexibility in Emotion Learning

Learners flexibly update category boundaries to adjust to the range of experiences they encounter. However, little is known about whether the degree of flexibility is consistent across domains. We examined whether categorization of social input, specifically emotions, is afforded more flexibility as compared to other biological input. To address this question, children (6-12 years; 32 female, 37 male; 7 Hispanic or Latino, 62 not Hispanic or Latino; 8 Black or African American, 14 multiracial, 46 White, 1 selected "other") categorized faces morphed from calm to upset and animals morphed from a horse to a cow across task phases that differed in the distribution of stimuli presented. Learners flexibly adjusted both emotion and animal category boundaries according to distributional information, yet children showed more flexibility when updating their category boundaries for emotions. These results provide support for the idea that children-who must adjust to the vast and varied emotional signals of their social partners-respond to social signals dynamically in order to make predictions about the internal states and future behaviors of others.

How sociolinguistic factors shape children's subjective impressions of teacher quality

When university students are asked to rate their instructors, their evaluations are often influenced by the demographic characteristics of the instructor-such as the instructor's race, gender, or language background. These influences can manifest in unfair systematic biases against particular groups of teachers and hamper movements to promote diversity in higher education. When and how do these biases develop? Here, we begin to address these questions by examining children's sociolinguistic biases against teachers who speak with different accents. To do this, we presented 5-year-old Canadian English-speaking children with pairs of adult talkers. Children were asked to select "who they'd like to be their teacher" then they rated "how good of a teacher" they thought each talker would be on a 5-point scale. In each trial, one talker spoke in the locally dominant variety of Canadian English, and the other spoke in a different accent. Children strongly preferred Canadian-accented teachers over teachers who spoke with non-native (i.e., French or Dutch) accents, but also demonstrated a preference for Canadian teachers over teachers who spoke with non-local regional accents (i.e., Australian or British). In line with the binary choice data, children rated the Canadian talkers more favourably. The relationship between the gender of the teacher and the gender of the child also impacted ratings. This work demonstrates that even at the onset of formal education, children may already exhibit signs of accent-based biases. We discuss these findings in relation to the growing literature on implicit bias in higher education.

The role of priming in grammatical acceptability judgements for native versus non-native speakers: Effects of intelligibility

Comprehenders frequently need to adapt to linguistic variability between talkers and dialects. Previous research has shown, given repeated exposure to quasi-grammatical structures, comprehenders begin to perceive them as more grammatical (Luka & Barsalou 2005, Luka & Choi 2012). We examined whether grammatical acceptability judgements differ for native versus non-native speech. In an exposure phase, native English speakers listened to, retyped, and rated the grammaticality of quasi-grammatical sentences (e.g., What Emily is thankful for is that she is here) spoken by a native or non-native speaker. In a subsequent test phase, participants rated additional sentences, some of which had the same structure as exposure sentences. Participants rated native-accented sentences as more grammatical, demonstrating a role for talker identity in perceptions of grammaticality. Furthermore, structures previously heard during the exposure phase were rated as more grammatical than novel unprimed structures, but only for the native speaker. Subset analyses suggest this effect is driven by speaker intelligibility, which holds implications for communication between native and non-native speakers.

Naturalistic speech supports distributional learning across contexts

At birth, infants discriminate most of the sounds of the world's languages, but by age 1, infants become language-specific listeners. This has generally been taken as evidence that infants have learned which acoustic dimensions are contrastive, or useful for distinguishing among the sounds of their language(s), and have begun focusing primarily on those dimensions when perceiving speech. However, speech is highly variable, with different sounds overlapping substantially in their acoustics, and after decades of research, we still do not know what aspects of the speech signal allow infants to differentiate contrastive from noncontrastive dimensions. Here we show that infants could learn which acoustic dimensions of their language are contrastive, despite the high acoustic variability. Our account is based on the cross-linguistic fact that even sounds that overlap in their acoustics differ in the contexts they occur in. We predict that this should leave a signal that infants can pick up on and show that acoustic distributions indeed vary more by context along contrastive dimensions compared with noncontrastive dimensions. By establishing this difference, we provide a potential answer to how infants learn about sound contrasts, a question whose answer in natural learning environments has remained elusive.

Children track probabilistic distributions of facial cues across individuals

Children face a difficult task in learning how to reason about other people's emotions. How intensely facial configurations are displayed can vary not only according to what and how much emotion people are experiencing, but also across individuals based on differences in personality, gender, and culture. To navigate these sources of variability, children may use statistical information about other's facial cues to make interpretations about perceived emotions in others. We examined this possibility by testing children's ability to adjust to differences in the intensity of facial cues across different individuals. In the present study, children (6- to 10-year-olds) categorized the information communicated by facial configurations of emotion varying continuously from "calm" to "upset," with differences in the intensity of each actor's facial movements. We found that children's threshold for categorizing a facial configuration as "upset" shifted depending on the statistical information encountered about each of the different individuals. These results suggest that children are able to track individual differences in facial behavior and use these differences to flexibly update their interpretations of facial cues associated with emotion. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Does race impact speech perception? An account of accented speech in two different multilingual locales

Upon hearing someone's speech, a listener can access information such as the speaker's age, gender identity, socioeconomic status, and their linguistic background. However, an open question is whether living in different locales modulates how listeners use these factors to assess speakers' speech. Here, an audio-visual test was used to measure whether listeners' accentedness judgments and intelligibility (i.e., speech perception) can be modulated depending on racial information in faces that they see. American, British, and Indian English were used as three different English varieties of speech. These speech samples were presented with either a white female face or a South Asian female face. Two experiments were completed in two locales: Gainesville, Florida (USA) and Montreal, Quebec (Canada). Overall, Montreal listeners were more accurate in their transcription of sentences (i.e., intelligibility) compared to Gainesville listeners. Moreover, Gainesville listeners' ability to transcribe the same spoken sentences decreased for all varieties when listening to speech paired with South Asian faces. However, seeing a white or a South Asian face did not impact speech intelligibility for the same spoken sentences for Montreal listeners. Finally, listeners' accentedness judgments increased for American English and Indian English when the visual information changed from a white face to a South Asian face in Gainesville, but not in Montreal. These findings suggest that visual cues for race impact speech perception to a greater degree in locales with greater ecological diversity.

Behavioral Pattern Analysis between Bilingual and Monolingual Listeners’ Natural Speech Perception on Foreign-Accented English Language Using Different Machine Learning Approaches

Speech perception in an adverse background/noisy environment is a complex and challenging human process, which is made even more complicated in foreign-accented language for bilingual and monolingual individuals. Listeners who have difficulties in hearing are affected most by such a situation. Despite considerable efforts, the increase in speech intelligibility in noise remains elusive. Considering this opportunity, this study investigates Bengali–English bilinguals and native American English monolinguals’ behavioral patterns on foreign-accented English language considering bubble noise, gaussian or white noise, and quiet sound level. Twelve regular hearing participants (Six Bengali–English bilinguals and Six Native American English monolinguals) joined in this study. Statistical computation shows that speech with different noise has a significant effect (p = 0.009) on listening for both bilingual and monolingual under different sound levels (e.g., 55 dB, 65 dB, and 75 dB). Here, six different machine learning approaches (Logistic Regression (LR), Linear Discriminant Analysis (LDA), K-nearest neighbors (KNN), Naïve Bayes (NB), Classification and regression trees (CART), and Support vector machine (SVM)) are tested and evaluated to differentiate between bilingual and monolingual individuals from their behavioral patterns in both noisy and quiet environments. Results show that most optimal performances were observed using LDA by successfully differentiating between bilingual and monolingual 60% of the time. A deep neural network-based model is proposed to improve this measure further and achieved an accuracy of nearly 100% in successfully differentiating between bilingual and monolingual individuals.

Are foreign-accented speakers that 'incredible'? The impact of the speaker's indexical properties on sentence processing

This study investigated the impact of the speaker's identity generated by the voice on sentence processing. We examined the relation between ERP components associated with the processing of the voice (N100 and P200) from voice onset and those associated with sentence processing (N400 and late positivity) from critical word onset. We presented Dutch native speakers with sentences containing true (and known) information, unknown (but true) information or information violating world knowledge and had them perform a truth evaluation task. Sentences were spoken either in a native or a foreign accent. Truth evaluation judgments were not different for statements spoken by the native-accented and the foreign-accented speakers. Reduced N100 and P200 were observed in response to the foreign speaker's voice compared to the native speaker's. While statements containing unknown information or world knowledge violations generated a larger N400 than true statements in the native condition, they were not significantly different in the foreign condition, suggesting shallower processing of foreign-accented speech. The N100 was a significant predictor for the N400 in that the reduced N100 observed for the foreign speaker compared to the native speaker was related to a smaller N400 effect. These finding suggest that the impression of the speaker that listeners rapidly form from the voice affects semantic processing, which confirms that speaker's identity and language comprehension cannot be dissociated.

Perception of accent in bilingual French/American-English children by native adult speakers

In a previous study, Dodane and Bijeljac-Babic (2017) found that French/AmericanEnglish children aged 3;6 to 6;0, bilingual from birth, produced disyllabic words which had acoustic properties for lexical stress (f0, syllable duration and intensity) that differed from those of monolingual peers, showing cross-linguistic influences. In order to check whether these acoustic differences between the productions of bilingual children and those of their monolingual French- or American English-speaking peers were perceptible by native monolingual adults, we investigated the perception of these words by French and American English native speakers. Using an Elo rating task, participants were asked to indicate in each trial which word out of two competitors was produced by a bilingual child. Words were produced by French- or American English-speaking monolingual children and by two groups of bilinguals, one dominant in French and the other in American-English. The results clearly show that both French and American English monolingual adults were successful in distinguishing the bilingual children from their monolingual peers, but only if they were not dominant in the language of the raters. The relationship between the acoustic correlates of word stress produced by children and the perception of some "accent" by native adult speakers seems more intricate than expected and is further discussed.

Targeted adaptation in infants following live exposure to an accented talker

Infants struggle to understand familiar words spoken in unfamiliar accents. Here, we examine whether accent exposure facilitates accent-specific adaptation. Two types of pre-exposure were examined: video-based (i.e., listening to pre-recorded stories; Experiment 1) and live interaction (reading books with an experimenter; Experiments 2 and 3). After video-based exposure, Canadian English-learning 15- to 18-month-olds failed to recognize familiar words spoken in an unfamiliar accent. However, after face-to-face interaction with a Mandarin-accented talker, infants showed enhanced recognition for words produced in Mandarin English compared to Australian English. Infants with live exposure to an Australian talker were not similarly facilitated, perhaps due to the lower vocabulary scores of the infants assigned to the Australian exposure condition. Thus, live exposure can facilitate accent adaptation, but this ability is fragile in young infants and is likely influenced by vocabulary size and the specific mapping between the speaker and the listener's phonological system.

Now You Hear Me, Later You Don't: The Immediacy of Linguistic Computation and the Representation of Speech

What happens to an acoustic signal after it enters the mind of a listener? Previous work has demonstrated that listeners maintain intermediate representations over time. However, the internal structure of such representations-be they the acoustic-phonetic signal or more general information about the probability of possible categories-remains underspecified. We present two experiments using a novel speaker-adaptation paradigm aimed at uncovering the format of speech representations. We exposed adult listeners (N = 297) to a speaker whose utterances contained acoustically ambiguous information concerning phones (and thus words), and we manipulated the temporal availability of disambiguating cues via visually presented text (presented before or after each utterance). Results from a traditional phoneme-categorization task showed that listeners adapted to a modified acoustic distribution when disambiguating text was provided before but not after the audio. These results support the position that speech representations consist of activation over categories and are inconsistent with direct maintenance of the acoustic-phonetic signal.

A New Proposal for Phoneme Acquisition: Computing Speaker-Specific Distribution

Speech is an acoustically variable signal, and one of the sources of this variation is the presence of multiple speakers. Empirical evidence has suggested that adult listeners possess remarkably sensitive (and systematic) abilities to process speech signals, despite speaker variability. It includes not only a sensitivity to speaker-specific variation, but also an ability to utilize speaker variation with other sources of information for further processing. Recently, many studies also showed that young children seem to possess a similar capacity. This suggests continuity in the processing of speaker-dependent speech variability, and suggests that this ability could also be important for infants learning their native language. In the present paper, we review evidence for speaker variability and speech processing in adults, and speaker variability and speech processing in young children, with an emphasis on how they make use of speaker-specific information in word learning situations. Finally, we will build on these findings to make a novel proposal for the use of speaker-specific information processing in phoneme learning in infancy.

Identification of Foreign-Accented Words in Preschoolers With and Without Speech Sound Disorders

Purpose The aim of this study was to investigate the ability of preschoolers with speech sound disorder (SSD) and with typical speech and language development (TD) to understand foreign-accented words, providing a window into the quality of their underlying phonological representations. We also investigated the relationship between vocabulary skills and the ability to identify words that are frequent and have few neighbors (lexically easy words) and words that are less frequent and have many neighbors (lexically hard words). Method Thirty-two monolingual English-speaking children (16 with SSD, 16 with TD), ages 4 and 5 years, completed standardized speech and language tests and a two-alternative forced-choice word identification task of English words produced by a native English speaker and a native Korean speaker. Results Children with SSD had more difficulty identifying words produced by both talkers than children with TD and showed a larger difficulty identifying Korean-accented words. Both groups of children identified lexically easy words more accurately than lexically hard words, although this difference was not significant when including receptive vocabulary skills in the analysis. Identification of lexically hard words, both those produced by the native English speaker and the nonnative English speaker, increased with vocabulary size. Conclusion Considering the performance of the children with SSD under ideal listening conditions in this study, we can assume that, as a group, children with SSD may experience greater difficulty identifying foreign-accented words in environments with background noise.

(Mis) understanding your native language: Regional accent impedes processing of information status

Native-speaker listeners constantly predict upcoming units of speech as part of language processing, using various cues. However, this process is impeded in second-language listeners, as well as when the speaker has an unfamiliar accent. Whereas previous research has largely concentrated on the pronunciation of individual segments in foreign-accented speech, we show that regional accent impedes higher levels of language processing, making native listeners' processing resemble that of second-language listeners.In Experiment 1, 42 native speakers of Canadian English followed instructions spoken in British English to move objects on a screen while their eye movements were tracked. Native listeners use prosodic cues to information status to disambiguate between two possible referents, a new and a previously mentioned one, before they have heard the complete word. By contrast, the Canadian participants, similarly to second-language speakers, were not able to make full use of prosodic cues in the way native British listeners do.In Experiment 2, 19 native speakers of Canadian English rated the British English instructions used in Experiment 1, as well as the same instructions spoken by a Canadian imitating the British English prosody. While information status had no effect for the Canadian imitations, the original stimuli received higher ratings when prosodic realization and information status of the referent matched than for mismatches, suggesting a native-like competence in these offline ratings.These findings underline the importance of expanding psycholinguistic models of second language/dialect processing and representation to include both prosody and regional variation.

Brain networks involved in accented speech processing

We investigated the neural correlates of accented speech processing (ASP) with an fMRI study that overcame prior limitations in this line of research: we preserved intelligibility by using two regional accents that differ in prosody but only mildly in phonetics (Latin American and Castilian Spanish), and we used independent component analysis to identify brain networks as opposed to isolated regions. ASP engaged a speech perception network composed primarily of structures related with the processing of prosody (cerebellum, putamen, and thalamus). This network also included anterior fronto-temporal areas associated with lexical-semantic processing and a portion of the inferior frontal gyrus linked to executive control. ASP also recruited domain-general executive control networks related with cognitive demands (dorsal attentional and default mode networks) and the processing of salient events (salience network). Finally, the reward network showed a preference for the native accent, presumably revealing people's sense of social belonging.

Effects of Language Background on the Development of Sociolinguistic Awareness: The Perception of Accent Variation in Monolingual and Multilingual 5- to 7-Year-Old Children

As a result of complex international migration patterns, listeners in large urban centres such as London, UK, likely encounter large amounts of variation in spoken language. However, although dealing with variation is crucial to communication, relatively little is known about how the ability to do this develops. Still less is known about how this might be affected by language background. The current study investigates whether early experience with variation, specifically growing up bilingually in London, affects accent categorization. Sixty children (30 monolingual, 30 bilingual) aged 5-7 years, were tested in their ability to comprehend and categorize talkers in 2 out of 3 accents: a home, unfamiliar regional and unfamiliar foreign-accented variety. All children demonstrated high, above-chance performance in the comprehension task, but language background significantly affected the children's ability to categorize talkers. Bilinguals were able to categorize talkers in all accent conditions, but although all children were able to understand the talkers, monolingual children were only able to categorize talkers in the home-foreign accent condition. Overall, the results are consistent with an approach in which gradient representations of accent variation emerge alongside an understanding of how variation is used meaningfully within a child's environment.

Expectations about the source of a speaker's accent affect accent adaptation

When encountering speakers whose accents differ from the listener's own, listeners initially show a processing cost, but that cost can be attenuated after short term exposure. The extent to which processing foreign accents (L2-accents) and within-language accents (L1-accents) is similar is still an open question. This study considers whether listeners' expectations about the source of a speaker's accent-whether the speaker is purported to be an L1 or an L2 speaker-affect intelligibility. Prior work has indirectly manipulated expectations about a speaker's accent through photographs, but the present study primes listeners with a description of the speaker's accent itself. In experiment 1, native English listeners transcribed Spanish-accented English sentences in noise under three different conditions (speaker's accent: monolingual L1 Latinx English, L1-Spanish/L2-English, no information given). Results indicate that, by the end of the experiment, listeners given some information about the accent outperformed listeners given no information, and listeners told the speaker was L1-accented outperformed listeners told to expect L2-accented speech. Findings are interpreted in terms of listeners' expectations about task difficulty, and a follow-up experiment (experiment 2) found that priming listeners to expect that their ability to understand L2-accented speech can improve does in fact improve intelligibility.

Processing of unfamiliar accents in monolingual and bilingual children: effects of type and amount of accent experience

Substantial individual differences exist in regard to type and amount of experience with variable speech resulting from foreign or regional accents. Whereas prior experience helps with processing familiar accents, research on how experience with accented speech affects processing of unfamiliar accents is inconclusive, ranging from perceptual benefits to processing disadvantages. We examined how experience with accented speech modulates mono- and bilingual children's (mean age: 9;10) ease of speech comprehension for two unfamiliar accents in German, one foreign and one regional. More experience with regional accents helped children repeat sentences correctly in the regional condition and in the standard condition. More experience with foreign accents did not help in either accent condition. The results suggest that type and amount of accent experience co-determine processing ease of accented speech.

Shhh… I Need Quiet! Children's Understanding of American, British, and Japanese-accented English Speakers

Children's ability to understand speakers with a wide range of dialects and accents is essential for efficient language development and communication in a global society. Here, the impact of regional dialect and foreign-accent variability on children's speech understanding was evaluated in both quiet and noisy conditions. Five- to seven-year-old children ( n = 90) and adults ( n = 96) repeated sentences produced by three speakers with different accents-American English, British English, and Japanese-accented English-in quiet or noisy conditions. Adults had no difficulty understanding any speaker in quiet conditions. Their performance declined for the nonnative speaker with a moderate amount of noise; their performance only substantially declined for the British English speaker (i.e., below 93% correct) when their understanding of the American English speaker was also impeded. In contrast, although children showed accurate word recognition for the American and British English speakers in quiet conditions, they had difficulty understanding the nonnative speaker even under ideal listening conditions. With a moderate amount of noise, their perception of British English speech declined substantially and their ability to understand the nonnative speaker was particularly poor. These results suggest that although school-aged children can understand unfamiliar native dialects under ideal listening conditions, their ability to recognize words in these dialects may be highly susceptible to the influence of environmental degradation. Fully adult-like word identification for speakers with unfamiliar accents and dialects may exhibit a protracted developmental trajectory.

Development of unfamiliar accent comprehension continues through adolescence

School-age children's understanding of unfamiliar accents is not adult-like and the age at which this ability fully matures is unknown. To address this gap, eight- to fifteen-year-old children's (n = 74) understanding of native- and non-native-accented sentences in quiet and noise was assessed. Children's performance was adult-like by eleven to twelve years for the native accent in noise and by fourteen to fifteen years for the non-native accent in quiet. However, fourteen- to fifteen-year old's performance was not adult-like for the non-native accent in noise. Thus, adult-like comprehension of unfamiliar accents may require greater exposure to linguistic variability or additional cognitive-linguistic growth.

Re-Examining Phonetic Variability in Native and Non-Native Speech

BACKGROUND/AIMS

Non-native speech is frequently characterized as being more variable than native speech. However, the few studies that have directly investigated phonetic variability in the speech of second language learners have considered a limited subset of native/non-native language pairings and few linguistic features.

METHODS

The present study examines group-level withinspeaker variability and central tendencies in acoustic properties of vowels andstops produced by learners of Japanese from two native language backgrounds, English and Mandarin, as well as native Japanese speakers.

RESULTS

Results show that non-native speakers do not always exhibit more phonetic variability than native speakers, but rather that patterns of variability are specific to individual linguistic features and their instantiations in L1 and L2.

CONCLUSION

Adopting this more nuanced approach to variability offers important enhancements to several areas of linguistic theory.

Unfamiliar Accented English Negatively Affects EFL Listening Comprehension: It Helps to be a More Able Accent Mimic

In this study, EFL learners who listened to four short context-rich audio files each delivered in an unfamiliar English accent were required to produce best-attempt transcriptions and accent imitation recordings. Results indicate that exposure alone does not suffice to eliminate accent impact on EFL listeners. Importantly, results from one-way ANOVA analyses reveal between-participants differences in residual accent impact, vocabulary knowledge, and quality of accent imitation. Results from a linear mixed-effects model analysis, while suggesting that other unidentified factors may also assist EFL listeners in processing unfamiliar accented English, demonstrate that the more able mimics cope more successfully with unfamiliar accents than the less able mimics. Counter-intuitively, vocabulary knowledge is rejected as a predictor for success in reducing accent impact. A logical explanation for this particular finding is that a larger vocabulary repertoire aids listeners where there is no interference from unfamiliar accents. Given these findings, to better prepare EFL listeners for the English-as-an-International-Language world, training should include both listening to a variety of native and non-native accents and performing accent imitation (reproduction) exercises to further expand listeners' phonological-phonetic flexibility.

Exposure to multiple accents supports infants' understanding of novel accents

Accented speech poses a challenge for listeners, particularly those with limited knowledge of their language. In a series of studies, we explored the possibility that experience with variability, specifically the variability provided by multiple accents, would facilitate infants' comprehension of speech produced with an unfamiliar accent. 15- and 18-month-old American-English learning infants were exposed to brief passages of multi-talker speech and subsequently tested on their ability to distinguish between real, familiar words and nonsense words, produced in either their native accent or an unfamiliar (British) accent. Exposure passages were produced in a familiar (American) accent, a single unfamiliar (British) accent or a variety of novel accents (Australian, Southern, Indian). While 15-month-olds successfully recognized real words spoken in a familiar accent, they never demonstrated comprehension of English words produced in the unfamiliar accent. 18-month-olds also failed to recognize English words spoken in the unfamiliar accent after exposure to the familiar or single unfamiliar accent. However, they succeeded after exposure to multiple unfamiliar accents, suggesting that as they get older, infants are better able to exploit the cues provided by variable speech. Increased variability across multiple dimensions can be advantageous for young listeners.

Adaptation to novel foreign-accented speech and retention of benefit following training: Influence of aging and hearing loss

Adaptation to speech with a foreign accent is possible through prior exposure to talkers with that same accent. For young listeners with normal hearing, short term, accent-independent adaptation to a novel foreign accent is also facilitated through exposure training with multiple foreign accents. In the present study, accent-independent adaptation is examined in younger and older listeners with normal hearing and older listeners with hearing loss. Retention of training benefit is additionally explored. Stimuli for testing and training were HINT sentences recorded by talkers with nine distinctly different accents. Following two training sessions, all listener groups showed a similar increase in speech perception for a novel foreign accent. While no group retained this benefit at one week post-training, results of a secondary reaction time task revealed a decrease in reaction time following training, suggesting reduced listening effort. Examination of listeners' cognitive skills reveals a positive relationship between working memory and speech recognition ability. The present findings indicate that, while this no-feedback training paradigm for foreign-accented English is successful in promoting short term adaptation for listeners, this paradigm is not sufficient in facilitation of perceptual learning with lasting benefits for younger or older listeners.

Influences of Cognitive Processing Capacities on Speech Perception in Young Adults

Foreign accent in speech often presents listeners with challenging listening conditions. Consequently, listeners may need to draw on additional cognitive resources in order to perceive and comprehend such speech. Previous research has shown that, for older adults, executive functions predicted perception of speech material spoken in a novel, artificially created (and therefore unfamiliar) accent. The present study investigates the influences of executive functions, information processing speed, and working memory on perception of unfamiliar foreign accented speech, in healthy young adults. The results showed that the executive processes of inhibition and switching, as well as information processing speed predict response times to both accented and standard sentence stimuli, while inhibition and information processing speed predict speed of responding to accented word stimuli. Inhibition and switching further predict accuracy in responding to accented word and standard sentence stimuli that has increased processing demand (i.e., nonwords and sentences with unexpected semantic content). These findings suggest that stronger abilities in aspects of cognitive functioning may be helpful for matching variable pronunciations of speech sounds to stored representations, for example by being able to manage the activation of incorrect competing representations and shifting to other possible matches.

The Effects of Language Experience and Speech Context on the Phonetic Accommodation of English-accented Spanish Voicing

Native speakers of Spanish with different amounts of experience with English classified stop-consonant voicing (/b/ versus /p/) across different speech accents: English-accented Spanish, native Spanish, and native English. While listeners with little experience with English classified target voicing with an English- or Spanish-like voice onset time (VOT) boundary, predicted by contextual VOT, listeners familiar with English relied on an English-like VOT boundary in an English-accented Spanish context even in the absence of clear contextual cues to English VOT. This indicates that Spanish listeners accommodated English-accented Spanish voicing differently depending on their degree of familiarization with the English norm.

Speaker and Accent Variation Are Handled Differently: Evidence in Native and Non-Native Listeners

Listeners are able to cope with between-speaker variability in speech that stems from anatomical sources (i.e. individual and sex differences in vocal tract size) and sociolinguistic sources (i.e. accents). We hypothesized that listeners adapt to these two types of variation differently because prior work indicates that adapting to speaker/sex variability may occur pre-lexically while adapting to accent variability may require learning from attention to explicit cues (i.e. feedback). In Experiment 1, we tested our hypothesis by training native Dutch listeners and Australian-English (AusE) listeners without any experience with Dutch or Flemish to discriminate between the Dutch vowels /I/ and /ε/ from a single speaker. We then tested their ability to classify /I/ and /ε/ vowels of a novel Dutch speaker (i.e. speaker or sex change only), or vowels of a novel Flemish speaker (i.e. speaker or sex change plus accent change). We found that both Dutch and AusE listeners could successfully categorize vowels if the change involved a speaker/sex change, but not if the change involved an accent change. When AusE listeners were given feedback on their categorization responses to the novel speaker in Experiment 2, they were able to successfully categorize vowels involving an accent change. These results suggest that adapting to accents may be a two-step process, whereby the first step involves adapting to speaker differences at a pre-lexical level, and the second step involves adapting to accent differences at a contextual level, where listeners have access to word meaning or are given feedback that allows them to appropriately adjust their perceptual category boundaries.

Children's comprehension of an unfamiliar speaker accent: a review

BACKGROUND

The effect of speaker accent on listeners' comprehension has become a key focus of research given the increasing cultural diversity of society and the increased likelihood of an individual encountering a clinician with an unfamiliar accent.

AIMS

To review the studies exploring the effect of an unfamiliar accent on language comprehension in typically developing (TD) children and in children with speech and language difficulties. This review provides a methodological analysis of the relevant studies by exploring the challenges facing this field of research and highlighting the current gaps in the literature.

METHODS & PROCEDURES

A total of nine studies were identified using a systematic search and organized under studies investigating the effect of speaker accent on language comprehension in (1) TD children and (2) children with speech and/or language difficulties.

MAIN CONTRIBUTION

This review synthesizes the evidence that an unfamiliar speaker accent may lead to a breakdown in language comprehension in TD children and in children with speech difficulties. Moreover, it exposes the inconsistencies found in this field of research and highlights the lack of studies investigating the effect of speaker accent in children with language deficits.

CONCLUSIONS & IMPLICATIONS

Overall, research points towards a developmental trend in children's ability to comprehend accent-related variations in speech. Vocabulary size, language exposure, exposure to different accents and adequate processing resources (e.g. attention) seem to play a key role in children's ability to understand unfamiliar accents. This review uncovered some inconsistencies in the literature that highlight the methodological issues that must be considered when conducting research in this field. It explores how such issues may be controlled in order to increase the validity and reliability of future research. Key clinical implications are also discussed.

Effects of contextual support on preschoolers' accented speech comprehension

Young children often hear speech in unfamiliar accents, but relatively little research characterizes their comprehension capacity. The current study tested preschoolers' comprehension of familiar-accented versus unfamiliar-accented speech with varying levels of contextual support from sentence frames (full sentences vs. isolated words) and from visual context (four salient pictured alternatives vs. the absence of salient visual referents). The familiar accent advantage was more robust when visual context was absent, suggesting that previous findings of good accent comprehension in infants and young children may result from ceiling effects in easier tasks (e.g., picture fixation, picture selection) relative to the more difficult tasks often used with older children and adults. In contrast to prior work on mispronunciations, where most errors were novel object responses, children in the current study did not select novel object referents above chance levels. This suggests that some property of accented speech may dissuade children from inferring that an unrecognized familiar-but-accented word has a novel referent. Finally, children showed detectable accent processing difficulty despite presumed incidental community exposure. Results suggest that preschoolers' accented speech comprehension is still developing, consistent with theories of protracted development of speech processing.

Early speech perception in Mandarin-speaking children at one-year post cochlear implantation

PURPOSE

The aim in this study was to examine early speech perception outcomes in Mandarin-speaking children during the first year of cochlear implant (CI) use.

METHOD

A hierarchical early speech perception battery was administered to 80 children before and 3, 6, and 12 months after implantation. Demographic information was obtained to evaluate its relationship with these outcomes.

RESULTS

Regardless of dialect exposure and whether a hearing aid was trialed before implantation, implant recipients were able to attain similar pre-lingual auditory skills after 12 months of CI use. Children speaking Mandarin developed early Mandarin speech perception faster than those with greater exposure to other Chinese dialects. In addition, children with better pre-implant hearing levels and younger age at implantation attained significantly better speech perception scores after 12 months of CI use. Better pre-implant hearing levels and higher maternal education level were also associated with a significantly steeper growth in early speech perception ability.

CONCLUSIONS

Mandarin-speaking children with CIs are able to attain early speech perception results comparable to those of their English-speaking counterparts. In addition, consistent single language input via CI probably enhances early speech perception development at least during the first-year of CI use.

Loss of regional accent after damage to the speech production network

Lesion-symptom mapping studies reveal that selective damage to one or more components of the speech production network can be associated with foreign accent syndrome, changes in regional accent (e.g., from Parisian accent to Alsatian accent), stronger regional accent, or re-emergence of a previously learned and dormant regional accent. Here, we report loss of regional accent after rapidly regressive Broca's aphasia in three Argentinean patients who had suffered unilateral or bilateral focal lesions in components of the speech production network. All patients were monolingual speakers with three different native Spanish accents (Cordobés or central, Guaranítico or northeast, and Bonaerense). Samples of speech production from the patient with native Córdoba accent were compared with previous recordings of his voice, whereas data from the patient with native Guaranítico accent were compared with speech samples from one healthy control matched for age, gender, and native accent. Speech samples from the patient with native Buenos Aires's accent were compared with data obtained from four healthy control subjects with the same accent. Analysis of speech production revealed discrete slowing in speech rate, inappropriate long pauses, and monotonous intonation. Phonemic production remained similar to those of healthy Spanish speakers, but phonetic variants peculiar to each accent (e.g., intervocalic aspiration of /s/ in Córdoba accent) were absent. While basic normal prosodic features of Spanish prosody were preserved, features intrinsic to melody of certain geographical areas (e.g., rising end F0 excursion in declarative sentences intoned with Córdoba accent) were absent. All patients were also unable to produce sentences with different emotional prosody. Brain imaging disclosed focal left hemisphere lesions involving the middle part of the motor cortex, the post-central cortex, the posterior inferior and/or middle frontal cortices, insula, anterior putamen and supplementary motor area. Our findings suggest that lesions affecting the middle part of the left motor cortex and other components of the speech production network disrupt neural processes involved in the production of regional accent features.

Neural bases of accented speech perception

The recognition of unfamiliar regional and foreign accents represents a challenging task for the speech perception system (Floccia et al., 2006; Adank et al., 2009). Despite the frequency with which we encounter such accents, the neural mechanisms supporting successful perception of accented speech are poorly understood. Nonetheless, candidate neural substrates involved in processing speech in challenging listening conditions, including accented speech, are beginning to be identified. This review will outline neural bases associated with perception of accented speech in the light of current models of speech perception, and compare these data to brain areas associated with processing other speech distortions. We will subsequently evaluate competing models of speech processing with regards to neural processing of accented speech. See Cristia et al. (2012) for an in-depth overview of behavioral aspects of accent processing.

Audiovisual cues benefit recognition of accented speech in noise but not perceptual adaptation

Perceptual adaptation allows humans to recognize different varieties of accented speech. We investigated whether perceptual adaptation to accented speech is facilitated if listeners can see a speaker's facial and mouth movements. In Study 1, participants listened to sentences in a novel accent and underwent a period of training with audiovisual or audio-only speech cues, presented in quiet or in background noise. A control group also underwent training with visual-only (speech-reading) cues. We observed no significant difference in perceptual adaptation between any of the groups. To address a number of remaining questions, we carried out a second study using a different accent, speaker and experimental design, in which participants listened to sentences in a non-native (Japanese) accent with audiovisual or audio-only cues, without separate training. Participants' eye gaze was recorded to verify that they looked at the speaker's face during audiovisual trials. Recognition accuracy was significantly better for audiovisual than for audio-only stimuli; however, no statistical difference in perceptual adaptation was observed between the two modalities. Furthermore, Bayesian analysis suggested that the data supported the null hypothesis. Our results suggest that although the availability of visual speech cues may be immediately beneficial for recognition of unfamiliar accented speech in noise, it does not improve perceptual adaptation.

Cognitive predictors of perceptual adaptation to accented speech

The present study investigated the effects of inhibition, vocabulary knowledge, and working memory on perceptual adaptation to accented speech. One hundred young, normal-hearing adults listened to sentences spoken in a constructed, unfamiliar accent presented in speech-shaped background noise. Speech Reception Thresholds (SRTs) corresponding to 50% speech recognition accuracy provided a measurement of adaptation to the accented speech. Stroop, vocabulary knowledge, and working memory tests were performed to measure cognitive ability. Participants adapted to the unfamiliar accent as revealed by a decrease in SRTs over time. Better inhibition (lower Stroop scores) predicted greater and faster adaptation to the unfamiliar accent. Vocabulary knowledge predicted better recognition of the unfamiliar accent, while working memory had a smaller, indirect effect on speech recognition mediated by vocabulary score. Results support a top-down model for successful adaptation to, and recognition of, accented speech; they add to recent theories that allocate a prominent role for executive function to effective speech comprehension in adverse listening conditions.

Revisiting vocal perception in non-human animals: a review of vowel discrimination, speaker voice recognition, and speaker normalization

The extent to which human speech perception evolved by taking advantage of predispositions and pre-existing features of vertebrate auditory and cognitive systems remains a central question in the evolution of speech. This paper reviews asymmetries in vowel perception, speaker voice recognition, and speaker normalization in non-human animals - topics that have not been thoroughly discussed in relation to the abilities of non-human animals, but are nonetheless important aspects of vocal perception. Throughout this paper we demonstrate that addressing these issues in non-human animals is relevant and worthwhile because many non-human animals must deal with similar issues in their natural environment. That is, they must also discriminate between similar-sounding vocalizations, determine signaler identity from vocalizations, and resolve signaler-dependent variation in vocalizations from conspecifics. Overall, we find that, although plausible, the current evidence is insufficiently strong to conclude that directional asymmetries in vowel perception are specific to humans, or that non-human animals can use voice characteristics to recognize human individuals. However, we do find some indication that non-human animals can normalize speaker differences. Accordingly, we identify avenues for future research that would greatly improve and advance our understanding of these topics.

Nonnative audiovisual speech perception in noise: dissociable effects of the speaker and listener

Nonnative speech poses a challenge to speech perception, especially in challenging listening environments. Audiovisual (AV) cues are known to improve native speech perception in noise. The extent to which AV cues benefit nonnative speech perception in noise, however, is much less well-understood. Here, we examined native American English-speaking and native Korean-speaking listeners' perception of English sentences produced by a native American English speaker and a native Korean speaker across a range of signal-to-noise ratios (SNRs;−4 to −20 dB) in audio-only and audiovisual conditions. We employed psychometric function analyses to characterize the pattern of AV benefit across SNRs. For native English speech, the largest AV benefit occurred at intermediate SNR (i.e. −12 dB); but for nonnative English speech, the largest AV benefit occurred at a higher SNR (−4 dB). The psychometric function analyses demonstrated that the AV benefit patterns were different between native and nonnative English speech. The nativeness of the listener exerted negligible effects on the AV benefit across SNRs. However, the nonnative listeners' ability to gain AV benefit in native English speech was related to their proficiency in English. These findings suggest that the native language background of both the speaker and listener clearly modulate the optimal use of AV cues in speech recognition.

A Neural Marker for Social Bias Toward In-group Accents

Accents provide information about the speaker's geographical, socio-economic, and ethnic background. Research in applied psychology and sociolinguistics suggests that we generally prefer our own accent to other varieties of our native language and attribute more positive traits to it. Despite the widespread influence of accents on social interactions, educational and work settings the neural underpinnings of this social bias toward our own accent and, what may drive this bias, are unexplored. We measured brain activity while participants from two different geographical backgrounds listened passively to 3 English accent types embedded in an adaptation design. Cerebral activity in several regions, including bilateral amygdalae, revealed a significant interaction between the participants' own accent and the accent they listened to: while repetition of own accents elicited an enhanced neural response, repetition of the other group's accent resulted in reduced responses classically associated with adaptation. Our findings suggest that increased social relevance of, or greater emotional sensitivity to in-group accents, may underlie the own-accent bias. Our results provide a neural marker for the bias associated with accents, and show, for the first time, that the neural response to speech is partly shaped by the geographical background of the listener.

Children's perception of foreign-accented words

The acoustic-phonetic realizations of words can vary dramatically depending on a variety of within- and across-talker characteristics such as regional dialect, native language, age, and gender. Robust word learning requires that children are able to recognize words amidst this substantial variability. In the current study, perception of foreign-accented words was assessed in four- to seven-year-old children to test how one form of variability influences word recognition in children. Results demonstrated that children had less accurate word recognition than adults for both native- and foreign-accented words. Both adults and children were less accurate at identifying foreign-accented words compared to native-accented words with children and adults showing similar decrements. For children, age and lexicon size contributed to accurate word recognition.

Magnitude of phonetic distinction predicts success at early word learning in native and non-native accents

Although infants perceptually attune to native vowels and consonants well before 12 months, at 13-15 months, they have difficulty learning to associate novel words that differ by their initial consonant (e.g., BIN and DIN) to their visual referents. However, this difficulty may not apply to all minimal pair novel words. While Canadian English (CE) 15-month-olds failed to respond to a switch from the newly learned word DEET to the novel non-word DOOT, they did notice a switch from DEET to DIT (Curtin et al., 2009). Those authors argued that early word learners capitalize on large phonetic differences, seen in CE DEET-DIT, but not on smaller phonetic differences, as in CE DEET-DOOT. To assess this hypothesis, we tested Australian English (AusE) 15-month-olds, as AusE has a smaller magnitude of phonetic difference in both novel word pairs. Two groups of infants were trained on the novel word DEET and tested on the vowel switches in DIT and DOOT, produced by an AusE female speaker or the same CE female speaker as in Curtin et al. (2009). If the size of the phonetic distinction plays a more central role than native accent experience in early word learning, AusE children should more easily recognize both of the unfamiliar but larger CE vowel switches than the more familiar but smaller AusE ones. The results support our phonetic-magnitude hypothesis: AusE children taught and tested with the CE-accented novel words looked longer to both of the switch test trials (DIT, DOOT) than same test trials (DEET), while those who heard the AusE-accented tokens did not notice either switch. Implications of our findings for models of early word learning are discussed.

Children's perception of dialect variation

A speaker's regional dialect is a rich source of information about that person. Two studies examined five- to six-year-old children's perception of regional dialect: Can they perceive differences among dialects? Have they made meaningful social connections to specific dialects? Experiment 1 asked children to categorize speakers into groups based on their accent; Experiment 2 asked them to match speakers to (un)familiar cultural items. Each child was tested with two of the following: the child's Home dialect, a Regional variant of that dialect, and a Second-Language variant. Results showed that children could successfully categorize only with a Home vs. Second-Language dialect contrast, but could reliably link cultural items with either a Home vs. Second-Language or a Regional vs. Second-Language dialect contrast. These results demonstrate five- to six-year-old children's developing perceptual skill with dialect, and suggest that they have a gradient representation of dialect variation.

A matched filter hypothesis for cognitive control

The prefrontal cortex exerts top-down influences on several aspects of higher-order cognition by functioning as a filtering mechanism that biases bottom-up sensory information toward a response that is optimal in context. However, research also indicates that not all aspects of complex cognition benefit from prefrontal regulation. Here we review and synthesize this research with an emphasis on the domains of learning and creative cognition, and outline how the appropriate level of cognitive control in a given situation can vary depending on the organism's goals and the characteristics of the given task. We offer a matched filter hypothesis for cognitive control, which proposes that the optimal level of cognitive control is task-dependent, with high levels of cognitive control best suited to tasks that are explicit, rule-based, verbal or abstract, and can be accomplished given the capacity limits of working memory and with low levels of cognitive control best suited to tasks that are implicit, reward-based, non-verbal or intuitive, and which can be accomplished irrespective of working memory limitations. Our approach promotes a view of cognitive control as a tool adapted to a subset of common challenges, rather than an all-purpose optimization system suited to every problem the organism might encounter.