Bilingual Talkers Research Articles

Language Ability and the Familiar Talker Advantage: Generalizing to Unfamiliar Talkers Is What Matters.

Purpose Previous studies with children and adults have demonstrated a familiar talker advantage-better word recognition for familiar talkers. The goal of the current study was to test whether this phenomenon is modulated by a child's language ability. Method Sixty children with a range of language ability were trained to learn the voices of 3 foreign-accented, German-English bilingual talkers and received feedback about their performance. Both before and after this talker voice training, children completed a spoken word recognition task in which they heard consonant-vowel-consonant words mixed with noise that were spoken by the 3 familiarized talkers and by 3 unfamiliar German-English bilinguals. Results Two findings emerged from this study: First, children with both higher and lower language ability performed similarly on the familiarized talkers. Second, children with higher language scores performed similarly on both the familiarized and unfamiliar talkers, whereas children with lower language scores performed worse on the unfamiliar talkers compared to familiar talkers, suggesting an inability to generalize to novel, unfamiliar talkers who spoke with a similar accent. Discussion Together, these findings indicate that children with higher language scores are able to generalize knowledge about foreign-accented talkers to help spoken word recognition for novel talkers with the same accent. In contrast, children with lower language skills did not exhibit the same magnitude of generalization. This lack of generalization to similar talkers may mean that children with lower language skills are at a disadvantage in spoken language tasks because they are unable to process speech as well when listening to unfamiliar talkers.

Identifying bilingual talkers after a language switch: Language experience matters.

The current study investigates the role of language experience in generalizing indexical information across languages within bilingual speech. Participants (n = 48) learned to identify bilingual talkers speaking in one of their languages and were then tested on their ability to identify the same talker when speaking the same language and when speaking their other language. Both monolingual and bilingual participants showed above chance performance in identifying the talkers in both language contexts. However, bilingual participants outperformed monolinguals in generalizing knowledge about the speaker's voice across their two familiar languages, which may be driven by their experience with language mixing.

Language-independent talker-specificity in bilingual speech intelligibility: Individual traits persist across first-language and second-language speech

The present study provides evidence of a positive correlation between L1 and L2 intelligibility for bilingual talkers. Each talker in a group of Mandarin-English and Korean-English bilinguals was recorded producing simple sentences in each of their languages. The recordings were then presented to native listeners of the language-being-spoken in a test of sentence-in-noise recognition to yield a pair of L1 and L2 intelligibility scores for each talker based on the proportion of words correctly recognized. For all talkers, their L2 speech (i.e., Mandarin- or Korean-accented English) was consistently lower in intelligibility than their L1 speech (i.e., native accented Mandarin or Korean). This dissociation between L1-L2 speech intelligibility was evident in different intelligibility scores at comparable signal-to-noise ratios (as much as 35 percentage points for the Mandarin-English bilinguals) and in the required boost in signal-to-noise ratio to achieve comparable intelligibility (>8–10 dB). Critically, L1 and L2 intelligibility scores within the bilingual talkers were strongly positively correlated: Talkers with relatively high intelligibility in L1 also achieved relatively high intelligibility in L2. These results indicate a persistent influence of talker-specific trait characteristics that combine with, rather than are overwhelmed by, language-specific and dominance-dependent influences in bilingual speech production.

Relation between acoustic-phonetic properties and speech intelligibility in noise obtained with bilingual talkers

An objective, language-independent way of predicting observed differences in speech intelligibility in noise across talkers based on their acoustic-phonetic properties was pursued by exploiting speech intelligibility data in stationary speech-shaped noise uttered by bilingual talkers and comparing inter-individual as well as intra-individual speech feature variations across languages. Matrix sentence materials were used that were uttered by bilingual talkers of German/Spanish and of German/Russian and by the respective original matrix test talkers. Various acoustic-phonetic parameters discussed in the literature as being related to speech intelligibility were determined for each talker. Vowel space area, between-vowel category dispersion, and energy in the mid-frequency region represented by the speech intelligibility index were found to be language-independent acoustic-phonetic properties most strongly related to speech intelligibility at least for German, Russian and Spanish. Generally larger inter-individual variation within languages than intra-individual variation across languages was found. Hence, objective phonetic criteria like vowel space area may be used in the future to objectively assess the potential of a talker to be easily understood in a noisy background. One reason of the generally poorer intelligibility performance of Spanish compared to German or Russian may lie in the usage of considerably smaller vowel space areas.

Language-independent talker-specificity in first-language and second-language speech production by bilingual talkers: L1 speaking rate predicts L2 speaking rate.

Second-language (L2) speech is consistently slower than first-language (L1) speech, and L1 speaking rate varies within- and across-talkers depending on many individual, situational, linguistic, and sociolinguistic factors. It is asked whether speaking rate is also determined by a language-independent talker-specific trait such that, across a group of bilinguals, L1 speaking rate significantly predicts L2 speaking rate. Two measurements of speaking rate were automatically extracted from recordings of read and spontaneous speech by English monolinguals (n = 27) and bilinguals from ten L1 backgrounds (n = 86): speech rate (syllables/second), and articulation rate (syllables/second excluding silent pauses). Replicating prior work, L2 speaking rates were significantly slower than L1 speaking rates both across-groups (monolinguals' L1 English vs bilinguals' L2 English), and across L1 and L2 within bilinguals. Critically, within the bilingual group, L1 speaking rate significantly predicted L2 speaking rate, suggesting that a significant portion of inter-talker variation in L2 speech is derived from inter-talker variation in L1 speech, and that individual variability in L2 spoken language production may be best understood within the context of individual variability in L1 spoken language production.

Language familiarity mediates identification of bilingual talkers across languages

Many studies show that listeners are more accurate at identifying talkers in their native language than in an unfamiliar language; yet, little is known about the nature of this language familiarity effect in bilingual speech. Here, we investigate the links between language and talker processing further by assessing listeners’ ability to identify bilingual talkers across languages. Two groups were recruited: English monolinguals and English-French bilinguals. Participants learned to identify bilinguals speaking in only one language (English); they were then tested on their ability to identify the same talkers speaking in the trained language (same language context: English) and in their other language (different language context: French). Both monolinguals and bilinguals showed above chance performance in identifying talkers in both language contexts at test, confirming that there is sufficient information in bilingual speech to generalize across languages. Moreover, the results showed a language context e...

Talker- and language-specific effects on speech intelligibility in noise assessed with bilingual talkers: Which language is more robust against noise and reverberation?

Objective: Investigate talker- and language-specific aspects of speech intelligibility in noise and reverberation using highly comparable matrix sentence tests across languages. Design: Matrix sentences spoken by German/Russian and German/Spanish bilingual talkers were recorded. These sentences were used to measure speech reception thresholds (SRTs) with native listeners in the respective languages in different listening conditions (stationary and fluctuating noise, multi-talker babble, reverberated speech-in-noise condition). Study sample: Four German/Russian and four German/Spanish bilingual talkers; 20 native German-speaking, 10 native Russian-speaking, and 10 native Spanish-speaking listeners. Results: Across-talker SRT differences of up to 6 dB were found for both groups of bilinguals. SRTs of German/Russian bilingual talkers were the same in both languages. SRTs of German/Spanish bilingual talkers were higher when they talked in Spanish than when they talked in German. The benefit from listening in the gaps was similar across all languages. The detrimental effect of reverberation was larger for Spanish than for German and Russian. Conclusions: Within the limitations set by the number and slight accentedness of talkers and other possible confounding factors, talker- and test-condition-dependent differences were isolated from the language effect: Russian and German exhibited similar intelligibility in noise and reverberation, whereas Spanish was more impaired in these situations.

Heritage bilingual talkers do not exhibit an intelligibility penalty in either language

Some speakers have clearer voices than others. In the present study, we investigate whether early bilingualism has systematic repercussions for talker clarity, using a group of Korean-American heritage bilingual talkers, as well as American and Korean (near-)monolinguals. American monolinguals and the bilinguals produced English sentences, which were mixed with white noise at two signal-to-noise ratios and presented to native English listeners. Korean monolinguals and the same bilinguals produced Korean sentences, which were presented to native Korean listeners. In English, there was no monolingual/bilingual difference in talker clarity. In Korean, bilingual talkers were more clear than monolinguals. Post hoc investigation showed that Korean American bilinguals produced the Korean stimuli more slowly than monolinguals, explaining part of the bilingual advantage. Taken together, these results suggest that early bilingual exposure does not cause a talker clarity deficit, in either language.

Talker familiarity and spoken word recognition in school-age children.

Research with adults has shown that spoken language processing is improved when listeners are familiar with talkers' voices, known as the familiar talker advantage. The current study explored whether this ability extends to school-age children, who are still acquiring language. Children were familiarized with the voices of three German-English bilingual talkers and were tested on the speech of six bilinguals, three of whom were familiar. Results revealed that children do show improved spoken language processing when they are familiar with the talkers, but this improvement was limited to highly familiar lexical items. This restriction of the familiar talker advantage is attributed to differences in the representation of highly familiar and less familiar lexical items. In addition, children did not exhibit accent-general learning; despite having been exposed to German-accented talkers during training, there was no improvement for novel German-accented talkers.

Perceptual integration of indexical information in bilingual speech

The present research examines how different types of indexical information, namely talker information and the language being spoken, are perceptually integrated in bilingual speech. Using a speeded classification paradigm [Garner (1974)], variability in characteristics of the talker (gender in experiment 1 and specific talker in experiment 2) and in the language being spoken (Mandarin vs. English) was manipulated. Listeners from two different language backgrounds, English monolinguals and Mandarin-English bilinguals, were asked to classify short, meaningful sentences obtained from different Mandarin-English bilingual talkers on these indexical dimensions. Results for the gender-language classification (Exp. 1) showed a significant, symmetrical interference effect for both listener groups, indicating that gender information and language are processed in an integral manner. For talker-language classification (Exp. 2), language interfered more with talker than vice versa for the English monolinguals, but symmetrical interference was found for the Mandarin-English bilinguals. These results suggest both that talker-specificity is not fully segregated from language-specificity, and that bilinguals exhibit more balanced classification along various indexical dimensions of speech. Currently, follow-up studies investigate this talker-language dependency for bilingual listeners who do not speak Mandarin in order to disentangle the role of bilingualism versus language familiarity.

The role of first-language production accuracy and talker-listener alignment in second-language speech Intelligibility

This study investigated variability in L2 speech intelligibility as a function of L1 speech intelligibility and of talker-listener L1 match. Non-native Korean talkers varying in their L2 proficiency were recorded reading simple English (L2) and Korean (L1) sentences. The intelligibility of these sentences was then assessed by Korean listeners (both Korean and English productions) and English listeners (English productions only) in a sentence recognition task. The results revealed that for these Korean-English bilingual talkers, L1 intelligibility was significantly correlated with L2 intelligibility for both Korean and English listeners, suggesting that variability in L1 speech intelligibility can serve as a predictor of variability in L2 production accuracy. We also examined the interlanguage speech intelligibility benefit for non-native listeners (ISIB-L) (e.g., Bent & Bradlow, 2003; Hayes-Harb et al., 2008). Korean listeners performed better at identifying the sentences produced by Korean talkers with relatively low L2 intelligibility, implying that the benefit of a shared native language between talkers and listeners may be larger when non-native listeners process speech from a talker with low L2 intelligibility. Overall, these findings indicate that variability in L2 speech intelligibility is related to language-general talker characteristics as well as to the talker-listener language alignment.

Talker discrimination across languages

This study investigated the extent to which listeners are able to discriminate between bilingual talkers in three language pairs – English–German, English–Finnish and English–Mandarin. Native English listeners were presented with two sentences spoken by bilingual talkers and were asked to judge whether they thought the sentences were spoken by the same person. Equal amounts of cross-language and matched-language trials were presented. The results show that native English listeners are able to carry out this task well; achieving percent correct levels at well above chance for all three language pairs. Previous research has shown this for English–German, this research shows listeners also extend this to Finnish and Mandarin, languages that are quite distinct from English from a genetic and phonetic similarity perspective. However, listeners are significantly less accurate on cross-language talker trials (English–foreign) than on matched-language trials (English–English and foreign–foreign). Understanding listeners’ behaviour in cross-language talker discrimination using natural speech is the first step in developing principled evaluation techniques for synthesis systems in which the goal is for the synthesised voice to sound like the original speaker, for instance, in speech-to-speech translation systems, voice conversion and reconstruction.

Effects of cross-language voice training on speech perception: whose familiar voices are more intelligible?

Previous research has shown that familiarity with a talker's voice can improve linguistic processing (herein, "Familiar Talker Advantage"), but this benefit is constrained by the context in which the talker's voice is familiar. The current study examined how familiarity affects intelligibility by manipulating the type of talker information available to listeners. One group of listeners learned to identify bilingual talkers' voices from English words, where they learned language-specific talker information. A second group of listeners learned the same talkers from German words, and thus only learned language-independent talker information. After voice training, both groups of listeners completed a word recognition task with English words produced by both familiar and unfamiliar talkers. Results revealed that English-trained listeners perceived more phonemes correct for familiar than unfamiliar talkers, while German-trained listeners did not show improved intelligibility for familiar talkers. The absence of a processing advantage in speech intelligibility for the German-trained listeners demonstrates limitations on the Familiar Talker Advantage, which crucially depends on the language context in which the talkers' voices were learned; knowledge of how a talker produces linguistically relevant contrasts in a particular language is necessary to increase speech intelligibility for words produced by familiar talkers.

Identification and discrimination of bilingual talkers across languages

This study investigated the extent to which language familiarity affects the perception of the indexical properties of speech by testing listeners' identification and discrimination of bilingual talkers across two different languages. In one experiment, listeners were trained to identify bilingual talkers speaking in only one language and were then tested on their ability to identify the same talkers speaking in another language. In the second experiment, listeners discriminated between bilingual talkers across languages in an AX discrimination paradigm. The results of these experiments indicate that there is sufficient language-independent indexical information in speech for listeners to generalize knowledge of talkers' voices across languages and to successfully discriminate between bilingual talkers regardless of the language they are speaking. However, the results of these studies also revealed that listeners do not solely rely on language-independent information when performing these tasks. Listeners use language-dependent indexical cues to identify talkers who are speaking a familiar language. Moreover, the tendency to perceive two talkers as the "same" or "different" depends on whether the talkers are speaking in the same language. The combined results of these experiments thus suggest that indexical processing relies on both language-dependent and language-independent information in the speech signal.

A cross-language familiar talker advantage

Previous research has shown that familiar talkers are more intelligible than unfamiliar talkers. In the current study, we tested the source of this familiar talker advantage by manipulating the type of talker information available to listeners. Two groups of native English listeners were familiarized with the voices of five German-English bilingual talkers; one group learned the voices from German stimuli and the other from English stimuli. Thus, English-trained listeners had access to both language-independent and English-specific talker information, while German-trained listeners had access to language-independent and German-specific talker information. After three days of voice learning, all listeners performed a word recognition task in English. Consistent with previous findings, English-trained listeners found the speech of familiar talkers to be more intelligible than unfamiliar talkers, as measured by whole words and phonemes correct. In contrast, German-trained listeners showed no familiar talker advantage, suggesting that listeners must have knowledge of talker-specific, linguistically relevant information to elicit the familiar talker advantage and that knowledge of language-independent talker information - such as size and shape of the vocal tract - does not facilitate speech perception.

Effects of clear speech on duration and fundamental frequency of vowels produced by monolingual and bilingual talkers

Prosodic characteristics of vowels produced by monolingual and bilingual talkers were investigated. Ten monolingual, 15 early Spanish-English bilingual (age of onset of immersion of age 12 or earlier), and ten late Spanish-English bilingual (age of onset of immersion of age 15 or later) talkers produced the target words ‘‘bead, bid, bayed, bed, bad,’’ and ‘‘bod’’ in conversational and clear speech styles. Vowel duration was computed, and F0 measurements were made at 20%, 50%, and 80% of the vowel duration. A significant group by style by vowel interaction showed that monolingual and early bilingual talkers enhanced inherent duration differences between target vowels by lengthening long vowels significantly more than short vowels in clear speech. The vowels of the late bilingual talkers, by contrast, became more alike in duration in clear than in conversational speech. The monolingual talkers showed a falling F0 pattern from 20% to 80% of the vowel duration in both styles; the late bilingual talkers showed a flat or rising F0 pattern in both styles; and the early bilingual talkers showed a flat or rising pattern in conversational speech, but a falling pattern in clear speech. [Work supported by NIH-NIDCD ♯5R03DC005561.]

Vowel space and formant dynamics of vowels produced by monolingual and bilingual talkers in conversational and clear speech styles

Formant frequency characteristics of vowels produced by monolingual and bilingual talkers were compared. Ten monolingual, 15 early Spanish-English bilingual (age of onset of immersion is 12 or earlier), and ten late Spanish-English bilingual (age of onset of immersion of age 15 or later) talkers produced the target words ‘‘bead, bid, bayed, bed, bad,’’ and ‘‘bod’’ in conversational and clear speech styles. Measurements of F1 and F2 were made at 20%, 50%, and 80% of vowel duration. Significant group effects for F1 and F2 at 50% of vowel duration showed similar locations and distances between the vowels for the monolingual and early bilingual talkers, except that F2 values were significantly higher for the early bilingual than for the monolingual talkers for the vowels in the target words ‘‘bead, bid,’’ and ‘‘bed.’’ Smaller between-vowel distances were found for both F1 and F2 for the late bilingual talkers, especially for the vowels in the target words ‘‘bead, bid, bayed,’’ and ‘‘bed.’’ Changes observed in clear speech were relatively modest for all three groups. Comparisons between formant dynamic vectors and angles across groups and style and between talkers showing large versus small degrees of clear speech intelligibility benefit will be presented. [Work supported by NIH-NIDCD No. 5R03DC005561.]

Clear speech effects for vowels produced by monolingual and bilingual talkers

The present study investigates the hypothesis that bilinguals may produce a smaller intelligibility benefit than monolinguals when asked to speak clearly. Three groups of talkers were recorded: 13 monolingual native English speakers, 22 early Spanish-English bilinguals, with an age of onset of learning English (AOL) of 12 or earlier, and 14 later Spanish-English bilinguals, with an AOL of 15 or later. Talkers produced the target words ‘‘bead, bid, bayed, bed, bad’’ and ‘‘bod’’ in both clear and conversational speech styles. Two repetitions of each target word were mixed with noise and presented to monolingual English-speaking listeners in a six-alternative forced-choice task across two days of testing. Stimuli were also presented in quiet on two subsequent days of testing. In preliminary data from 13 listeners, the early bilinguals were slightly more intelligible in noise than the monolingual talkers, with both groups showing a similar degree of clear speech benefit. Later bilinguals were less intelligible overall and showed a much smaller clear speech benefit in noise. These data suggest that later bilinguals, but not early bilinguals, may experience a disadvantage when speaking in noise due to a reduced ability to improve intelligibility by speaking more clearly [Work supported by NIH].

The speech learning model: English and Japanese voice onset time in mature bilingual talkers

With reference to the Speech Learning Model (Flege, 1995 version), this study looked for evidence among mature American and Japanese bilinguals that (a) L1 VOT changed over time and (b) despite minimal L1-L2 phonetic differences, L2 VOT was different from L1 VOT. Five L1 English Americans and 5 L1 Japanese read the same lists of English and Japanese words containing word initial /p/, /t/, and /k/. In all, 880 tokens (10 talkers ×2 languages ×11 words ×4 tokens) were examined. For both groups and individuals, based on measures of difference and comparisons with age-matched monolinguals (5 American and 13 Japanese), the findings were (a) slight evidence of L1 VOT change, but (b) robust evidence of new L2 categories being formed. By far the most common bilingual pattern observed was L2 compromise VOT, in which the L1 VOT remained close to monolingual VOT and the L2 VOT was positioned about halfway between that of two age-matched monolingual comparison groups.

Children’s abilities to distinguish novel languages

When adults hear spoken samples of a language which they do not know, they can often identify it and discriminate between languages even when produced by the same talkers. Children have much less experience making metalinguistic judgments. How do children respond to languages which they do not know? We have conducted three experiments examining the abilities of 4-year old and 8-year old children to discriminate between spoken samples of different languages produced by bilingual talkers. We constructed listening tests from 5-second phrases excerpted from fluent reading provided by the talkers. In the three experiments, we progressively simplified the response mode employed by the children as well as the cognitive load of the task. Even in the simplest version, only a third of the 4-year-olds could do the task while the 8-year old children performed above chance in all three experiments. The younger children tended to respond different more than same, as if their criterion for same was identify.