Neurophysiological marker of inhibition distinguishes language groups on a non-linguistic executive function test

Successful interaction with the environment depends on flexible behaviors which require shifting attention, inhibiting primed responses, ignoring distracting information, and withholding motor responses. These abilities, termed executive function (EF), are believed to be mediated by inhibitory processes in the frontal lobes. Superior performance on EF tests (i.e., faster reaction times (RT), and fewer errors) has been shown in bilinguals compared to monolingual speakers. However, findings are inconsistent, and no study has directly linked this bilingual advantage to frontal lobe inhibitory processes. To clarify this uncertainty, we concomitantly tested neural inhibitory processes and behavioral responses on an EF test in bilinguals and monolinguals. Specifically, we compared English monolinguals (N = 15) to Spanish/English bilinguals (N = 13) on event-related brain potentials (ERP) during a non-linguistic, auditory Go/NoGo task, a task linked to non-motor, cognitive inhibition in monolinguals. Participants responded with a button press on trials in which target tone-pairs (Go trials) were presented and withheld their responses on non-target trials (NoGo trials). Results revealed significantly greater inhibition (i.e., greater mean N2 amplitude) in bilinguals compared to monolinguals during NoGo trials even though both groups performed the task equally well (i.e., withheld a motor response). On Go trials where participants pressed a response button, neither ERPs nor RT distinguished the groups. Additionally, scores on a second language proficiency test (i.e., English in our bilingual group) were positively correlated with N2 amplitude. These findings are the first to directly link this bilingual advantage to a neural correlate of inhibition and to reveal that inhibition in bilinguals is moderated by second language proficiency. Results are discussed in the context of plasticity, and we propose that evaluating bilinguals at varying levels of second-language proficiency may serve as a model of human neuroplasticity.     

Neurophysiological marker of inhibition distinguishes language groups on a non-linguistic executive function test

Successful interaction with the environment depends on flexible behaviors which require shifting attention, inhibiting primed responses, ignoring distracting information, and withholding motor responses. These abilities, termed executive function (EF), are believed to be mediated by inhibitory processes in the frontal lobes. Superior performance on EF tests (i.e., faster reaction times (RT), and fewer errors) has been shown in bilinguals compared to monolingual speakers. However, findings are inconsistent, and no study has directly linked this bilingual advantage to frontal lobe inhibitory processes. To clarify this uncertainty, we concomitantly tested neural inhibitory processes and behavioral responses on an EF test in bilinguals and monolinguals. Specifically, we compared English monolinguals (N = 15) to Spanish/English bilinguals (N = 13) on event-related brain potentials (ERP) during a non-linguistic, auditory Go/NoGo task, a task linked to non-motor, cognitive inhibition in monolinguals. Participants responded with a button press on trials in which target tone-pairs (Go trials) were presented and withheld their responses on non-target trials (NoGo trials). Results revealed significantly greater inhibition (i.e., greater mean N2 amplitude) in bilinguals compared to monolinguals during NoGo trials even though both groups performed the task equally well (i.e., withheld a motor response). On Go trials where participants pressed a response button, neither ERPs nor RT distinguished the groups. Additionally, scores on a second language proficiency test (i.e., English in our bilingual group) were positively correlated with N2 amplitude. These findings are the first to directly link this bilingual advantage to a neural correlate of inhibition and to reveal that inhibition in bilinguals is moderated by second language proficiency. Results are discussed in the context of plasticity, and we propose that evaluating bilinguals at varying levels of second-language proficiency may serve as a model of human neuroplasticity.     

What's different in second-language processing? Evidence from event-related brain potentials

German sentences which were either correct, contained a selectional restriction violation, or a word category violation were presented auditorily to 16 native speakers of German (L1 group) and to 16 native speakers of Russian, who had learned German after the age of 10 (L2 group). Semantic violations elicited an N400 effect for both groups, but with a reduced amplitude and a longer peak latency in the L2 group. Compared to correct sentences, sentences with a phrase structure violation elicited an early anterior negativity followed by a broad centro-parietal positivity in native speakers. By contrast, there was no differential modulation of the early anterior negativity in the L2 group. A late positivity was also elicited in the second language learners, but it was slightly delayed compared to that shown by native speakers. This pattern is discussed in terms of different degrees of automaticity with respect to the subprocesses involved in sentence comprehension.     

Effects of speed of word processing on semantic access: the case of bilingualism

Bilingual speakers generally manifest slower word recognition than monolinguals. We investigated the consequences of the word processing speed on semantic access in bilinguals. The paradigm involved a stream of English words and pseudowords presented in succession at a constant rate. English-Welsh bilinguals and English monolinguals were asked to count the number of letters in pseudowords and actively disregard words. They were not explicitly told that pairs of words in immediate succession were embedded and could either be semantically related or not. We expected that slower word processing in bilinguals would result in semantic access indexed by semantic priming. As expected, bilinguals showed significant semantic priming, indexed by an N400 modulation, whilst monolinguals did not. Moreover, bilinguals were slower in performing the task. The results suggest that bilinguals cannot discriminate between pseudowords and words without accessing semantic information whereas monolinguals can dismiss English words on the basis of subsemantic information.     

On the Functional Equivalence of Monolinguals and Bilinguals in "Monolingual Mode": The Bilingual Anticipation Effect in Picture-Word Processing

Previous evidence indicates that bilinguals are slowed when an unexpected language switch occurs when they are reading aloud. This anticipation effect was investigated using a picture-word translation task to compare English monolinguals and Spanish-English bilinguals functioning in "monolingual mode." Monolinguals and half of the bilinguals drew pictures or wrote English words for picture or English word stimuli; the remaining bilinguals drew pictures or wrote Spanish words for picture or Spanish word stimuli. Production onset latency was longer in cross-modality translation than within-modality copying, and the increments were equivalent between groups across stimulus and production modalities. Assessed within participants, bilinguals were slower than monolinguals under intermixed but not under blocked trial conditions. Results indicate that the bilingual anticipation effect is not specific to language-mixing tasks. More generally, stimulus-processing uncertainty prevents establishment of a "base" symbolic-system procedure (concerning recognition, production, and intervening translation) and the inhibition of others. When this uncertainty is removed, bilinguals exhibit functional equivalence to monolinguals.     

Bilinguals Show Weaker Lexical Access During Spoken Sentence Comprehension

When bilinguals process written language, they show delays in accessing lexical items relative to monolinguals. The present study investigated whether this effect extended to spoken language comprehension, examining the processing of sentences with either low or high semantic constraint in both first and second languages. English-German bilinguals, German-English bilinguals and English monolinguals listened for target words in spoken English sentences while their eye-movements were recorded. Bilinguals’ eye-movements reflected weaker lexical access relative to monolinguals; furthermore, the effect of semantic constraint differed across first versus second language processing. Specifically, English-native bilinguals showed fewer overall looks to target items, regardless of sentence constraint; German-native bilinguals activated target items more slowly and maintained target activation over a longer period of time in the low-constraint condition compared with monolinguals. No eye movements to cross-linguistic competitors were observed, suggesting that these lexical access disadvantages were present during bilingual spoken sentence comprehension even in the absence of overt interlingual competition.     

Language learning and control in monolinguals and bilinguals

Parallel language activation in bilinguals leads to competition between languages. Experience managing this interference may aid novel language learning by improving the ability to suppress competition from known languages. To investigate the effect of bilingualism on the ability to control native-language interference, monolinguals and bilinguals were taught an artificial language designed to elicit between-language competition. Partial activation of interlingual competitors was assessed with eye-tracking and mouse-tracking during a word recognition task in the novel language. Eye-tracking results showed that monolinguals looked at competitors more than bilinguals, and for a longer duration of time. Mouse-tracking results showed that monolinguals' mouse movements were attracted to native-language competitors, whereas bilinguals overcame competitor interference by increasing the activation of target items. Results suggest that bilinguals manage cross-linguistic interference more effectively than monolinguals. We conclude that language interference can affect lexical retrieval, but bilingualism may reduce this interference by facilitating access to a newly learned language.     

Characterizing the Bilingual Disadvantage in Noun Phrase Production

Up to now, evidence on bilingual disadvantages in language production comes from tasks requiring single word retrieval. The present study aimed to assess whether there is a bilingual disadvantage in multiword utterances, and to determine the extent to which such effect is present in onset latencies, articulatory durations, or both. To do so, we tested two groups of Spanish speakers (monolinguals and early highly proficient bilinguals using their first and dominant language) each in two different production tasks: bare noun and noun phrase production. Onset latencies were longer for bilinguals relative to monolinguals in both production tasks. Regarding articulatory durations, we observed a clear bilingual disadvantage in noun phrase production and a strong tendency in bare noun production. These findings generalize the bilingual disadvantage in speech production to various performance measures (onset latency and articulatory duration of production) and beyond single words.     

Visual word recognition in bilinguals: evidence from masked phonological priming

Bilingual written language representation was investigated with the masked phonological priming paradigm. Pseudohomophonic and control primes of French target words were used to show that Dutch-French bilinguals exhibit the same pattern of phonological and orthographic priming as native French speakers, which suggests that the same processes underlie first-and second-language processing. It was also found that for bilinguals, but not monolinguals, it is possible to prime a target word of the second language with a homophonic stimulus (either word or nonword) of the first language. This interlingual phonological priming effect was of the same size as the intralingual priming effect. Implications for theories of bilingual written language representation and for the interpretation of the masked phonological priming paradigm are discussed.     

Accessing word meaning in two languages: an event-related brain potential study of beginning bilinguals

Twenty-eight native-English speakers enrolled in beginning and intermediate university Spanish courses participated in a mixed language semantic categorization task in which critical words were presented in English (L1) and Spanish (L2) and repetitions of these words (within- and between-languages) were presented on subsequent trials (i.e., immediate repetition). Event-related potentials were recorded to all items allowing for comparisons of the N400 component to repetitions within- and between-languages as well as to words presented for the first time. Three important findings were observed in this sample of participants during relatively early stages of acquiring a second language. First, in the typical N400 window (300-500ms), between-language repetition (translation) produced a smaller reduction in N400 amplitude than did within-language repetition. Second, the time-course of between-language repetition effects tended to be more extended in time and differed as a function of language with L2-L1 repetitions producing larger priming effects early (during the typical N400 window) and L1-L2 repetitions producing larger priming effects later (during windows after the typical N400). Third, a greater negativity in the ERP waveforms was observed when the word on the directly preceding trial was from the other language. Within the time frame of the N400, this language switch effect arose only when the target word was Spanish and the preceding word English (i.e., L1-L2). The results are discussed within the framework of current models of bilingual lexical processing.     

Does bilingualism hamper lexical access in speech production?

In the present study, we tested the hypothesis that bilingualism may cause a linguistic disadvantage in lexical access even for bilinguals' first and dominant language. To this purpose, we conducted a picture naming experiment comparing the performance of monolinguals and highly-proficient, L1-dominant bilinguals. The results revealed that monolinguals name pictures faster than bilinguals, both when bilinguals perform picture naming in their first and dominant language and when they do so in their weaker second language. This is the first time it has been demonstrated that bilinguals show a naming disadvantage in their L1 in comparison to monolingual speakers.     

Cognitive control and word recognition speed influence the Stroop effect in bilinguals

Bilinguals have been shown to be less susceptible to Stroop interference in their first language than monolinguals, though the cause is currently being debated. In two experiments, we explored how cognitive control and word recognition contribute to the Stroop effect by contrasting cognitive control (via a Simon arrow task), word recognition speed (via a Chinese/English word recognition task) and Stroop susceptibility (via a verbal Stroop task) between proficient and non‐proficient Chinese–English bilinguals. Compared to non‐proficient bilinguals, proficient bilinguals showed better cognitive control at inhibiting irrelevant information, and they were slower at recognising Chinese words but quicker at recognising English words. Critically, we also showed that proficient bilinguals showed a smaller Stroop effect than non‐proficient bilinguals in Chinese but a comparable Stroop effect as non‐proficient bilinguals in English. The results cannot be accounted for by cognitive control or word recognition speed alone; instead, they are best accommodated by assuming that cognitive control and word recognition speed jointly determine the Stroop effect. Thus, we conclude that enhanced cognitive control and delayed word recognition combine to reduce Stroop effect in bilinguals as compared to monolinguals.     

Laterality differences for word identification in bilinguals

Twenty-three Spanish-English bilinguals were tachistoscopically presented with four-letter common nouns. They viewed 20 word pairs, first in their native language, then in the other, for 40 msec under simultaneous bilateral exposure. This paradigm has previously shown a strong right visual field and therefore left hemisphere superiority for words in a single language. The results show a word identification advantage in the right visual field. This indicates a left hemisphere advantage for processing of both languages, regardless of which was learned first. There are nevertheless wide individual differences in the number of bilinguals showing the expected asymmetry, as compared with monolinguals. There may be a trend, therefore, for less unilaterality of language function in bilinguals, although both languages are seen as being equally lateralized.     

Incidental memory for format of presentation of number stimuli: Evidence from monolinguals and bilinguals

Are numerical stimuli represented in an abstract code or is information about surface format preserved in memory? Three experiments bearing on this issue are reported. All used an incidental recall procedure. Two experiments examined memory for numeral versus word format in monolinguals and the third examined memory for words in the first versus second language of Spanish-English bilinguals. Across all studies, memory for format of number presentation was above chance and was as high as 76% under certain conditions. Implications for number representation are discussed.     

第二语言水平对双语者语言抑制能力的影响——来自英语–汉语单通道双语者和英语–美国手语双通道双语者的证据

采用同形异义词干扰任务考察第二语言水平对英语–汉语单通道双语者和英语–美国手语双通道双语者语言抑制能力的影响。结果发现:(1)高水平英语–汉语单通道双语者的语言抑制能力较强,但低水平英语–汉语单通道双语者与英语单语者的语言抑制能力没有显著差异,说明少量的双语经验不足以导致双语认知优势;(2)不同水平的英语–美国手语双通道双语者的语言抑制能力差异不显著。所以如此,与英语–美国手语双通道双语者不存在口语和手语的双语表征加工竞争有关。整个研究表明,双语认知优势效应与双语者的二语水平以及通道经验有关。     

Is Semantic Processing During Sentence Reading Autonomous or Controlled? Evidence from the N400 Component in a Dual Task Paradigm

The present study contributes to the discussion on the automaticity of semantic processing. Whereas most previous research investigated semantic processing at word level, the present study addressed semantic processing during sentence reading. A dual task paradigm was combined with the recording of event-related brain potentials. Previous research at word level processing reported different patterns of interference with the N400 by additional tasks: attenuation of amplitude or delay of latency. In the present study, we presented Spanish sentences that were semantically correct or contained a semantic violation in a critical word. At different intervals preceding the critical word a tone was presented that required a high-priority choice response. At short intervals/high temporal overlap between the tasks mean amplitude of the N400 was reduced relative to long intervals/low temporal overlap, but there were no shifts of peak latency. We propose that processing at sentence level exerts a protective effect against the additional task. This is in accord with the attentional sensitization model (Kiefer & Martens, 2010), which suggests that semantic processing is an automatic process that can be enhanced by the currently activated task set. The present experimental sentences also induced a P600, which is taken as an index of integrative processing. Additional task effects are comparable to those in the N400 time window and are briefly discussed.     

Use of orthographic redundancies and word identification speed in bilinguals

The present study aimed at evidencing some of the factors linked to word identification speed in bilinguals. The performances of beginning and of skilled bilinguals on tasks related to single-word decoding were assessed in both the first and the second language. Results of a first experiment showed that whereas both groups of bilinguals demonstrated use of orthographic redundancies specific to their native language, only the skilled group did so as concerns second-language redundancies. It was seen in a second experiment, however, that the use or nonuse of orthographic structure cannot in itself account for the pattern of lexical decision latencies observed for words in the two languages. Rather, this pattern is consistent with the idea that word recognition latency is largely dependent upon subjects' past experience with and actual use of words.     

Contextual modulation of N400 amplitude to lexically ambiguous words

Though much is known about the N400 component, an event-related EEG potential that is sensitive to semantic manipulations, it is unclear whether modulations of N400 amplitude reflect automatic processing, controlled processing, or both. We examined this issue using a semantic judgment task that manipulated local and global contextual cues. Word triplets (prime-noun-target, e.g., finance-bank-money) were sequentially presented on a computer screen (500 ms duration, 1000 ms stimulus onset asynchrony), in which the second word was a homograph. The first word (prime) created a neutral-, dominant-meaning- or subordinate-meaning-biased "global context," and the third word (target) created a dominant- or subordinate-biased "local context" that was either congruent or incongruent with the "global context" established by the first prime word. Participants were instructed to read all three words but to decide only whether the second and third words were semantically related. Event-related potentials (ERPs), specifically the N400, were recorded to the third terminal word. N400 amplitudes evoked by dominant meaning-related third words incongruent with the globally biased subordinate context (e.g., river-bridge-money) were significantly more negative than dominant endings in neutral contexts (e.g., taxi-bank-money), but not different from unrelated filler triplets. In addition, there was some indication that left hemisphere, temporal-parietal electrode sites were associated with greater N400 negativity for dominant targets in conflicting subordinate global contexts than homologous right hemisphere electrode sites, the latter of which showed significant activation to subordinate meanings in cooperating contexts. Thus, N400 amplitude was more affected by global than local context suggesting that controlled processes may take priority over automatic processes in modulating N400 amplitude, especially for left hemisphere electrode sites.     

双语和双言对图片命名和分类的不对称影响

采用普通话-英语双语者、粤语-普通话双言者和普通话单言者为被试, 比较他们图片命名与图片分类的成绩。结果表明, 普通话-英语双语者用优势语言命名图片的反应时比普通话单语者显著长, 错误率显著高。在第4次和第5次重复呈现图片时, 普通话-英语双语者与普通话单语者的命名反应差异不显著。普通话-英语双语者与普通话单语者对图片分类的反应差异不显著。这表明, 双语影响图片命名却不影响图片分类。粤语-普通话双言者对图片命名和图片分类的反应模式和普通话-英语双语者一致, 表明粤语-普通话双言和普通话-英语双语有类似的认知机制。普通话和粤语是作为两种语言储存在粤语-普通话双言者的头脑中的。     

Knowledge of a second language influences auditory word recognition in the native language

Many studies in bilingual visual word recognition have demonstrated that lexical access is not language selective. However, research on bilingual word recognition in the auditory modality has been scarce, and it has yielded mixed results with regard to the degree of this language nonselectivity. In the present study, we investigated whether listening to a second language (L2) is influenced by knowledge of the native language (L1) and, more important, whether listening to the L1 is also influenced by knowledge of an L2. Additionally, we investigated whether the listener's selectivity of lexical access is influenced by the speaker's L1 (and thus his or her accent). With this aim, Dutch-English bilinguals completed an English (Experiment 1) and a Dutch (Experiment 3) auditory lexical decision task. As a control, the English auditory lexical decision task was also completed by English monolinguals (Experiment 2). Targets were pronounced by a native Dutch speaker with English as the L2 (Experiments 1A, 2A, and 3A) or by a native English speaker with Dutch as the L2 (Experiments 1B, 2B, and 3B). In all experiments, Dutch-English bilinguals recognized interlingual homophones (e.g., lief [sweet]-leaf /li:f/) significantly slower than matched control words, whereas the English monolinguals showed no effect. These results indicate that (a) lexical access in bilingual auditory word recognition is not language selective in L2, nor in L1, and (b) language-specific subphonological cues do not annul cross-lingual interactions.