The Presence of Background Noise Extends the Competitor Space in Native and Non-Native Spoken-Word Recognition: Insights from Computational Modeling

Neural Representations of Non-native Speech Reflect Proficiency and Interference from Native Language Knowledge

Learning to process speech in a foreign language involves learning new representations for mapping the auditory signal to linguistic structure. Behavioral experiments suggest that even listeners that are highly proficient in a non-native language experience interference from representations of their native language. However, much of the evidence for such interference comes from tasks that may inadvertently increase the salience of native language competitors. Here we tested for neural evidence of proficiency and native language interference in a naturalistic story listening task. We studied electroencephalography responses of 39 native speakers of Dutch (14 male) to an English short story, spoken by a native speaker of either American English or Dutch. We modeled brain responses with multivariate temporal response functions, using acoustic and language models. We found evidence for activation of Dutch language statistics when listening to English, but only when it was spoken with a Dutch accent. This suggests that a naturalistic, monolingual setting decreases the interference from native language representations, whereas an accent in the listener's own native language may increase native language interference, by increasing the salience of the native language and activating native language phonetic and lexical representations. Brain responses suggest that such interference stems from words from the native language competing with the foreign language in a single word recognition system, rather than being activated in a parallel lexicon. We further found that secondary acoustic representations of speech (after 200 ms latency) decreased with increasing proficiency. This may reflect improved acoustic-phonetic models in more proficient listeners.Significance Statement Behavioral experiments suggest that native language knowledge interferes with foreign language listening, but such effects may be sensitive to task manipulations, as tasks that increase metalinguistic awareness may also increase native language interference. This highlights the need for studying non-native speech processing using naturalistic tasks. We measured neural responses unobtrusively while participants listened for comprehension and characterized the influence of proficiency at multiple levels of representation. We found that salience of the native language, as manipulated through speaker accent, affected activation of native language representations: significant evidence for activation of native language (Dutch) categories was only obtained when the speaker had a Dutch accent, whereas no significant interference was found to a speaker with a native (American) accent.

Recognizing non-native spoken words in background noise increases interference from the native language

Listeners frequently recognize spoken words in the presence of background noise. Previous research has shown that noise reduces phoneme intelligibility and hampers spoken-word recognition - especially for non-native listeners. In the present study, we investigated how noise influences lexical competition in both the non-native and the native language, reflecting the degree to which both languages are co-activated. We recorded the eye movements of native Dutch participants as they listened to English sentences containing a target word while looking at displays containing four objects. On target-present trials, the visual referent depicting the target word was present, along with three unrelated distractors. On target-absent trials, the target object (e.g., wizard) was absent. Instead, the display contained an English competitor, overlapping with the English target in phonological onset (e.g., window), a Dutch competitor, overlapping with the English target in phonological onset (e.g., wimpel, pennant), and two unrelated distractors. Half of the sentences was masked by speech-shaped noise; the other half was presented in quiet. Compared to speech in quiet, noise delayed fixations to the target objects on target-present trials. For target-absent trials, we observed that the likelihood for fixation biases towards the English and Dutch onset competitors (over the unrelated distractors) was larger in noise than in quiet. Our data thus show that the presence of background noise increases lexical competition in the task-relevant non-native (English) and in the task-irrelevant native (Dutch) language. The latter reflects stronger interference of one's native language during non-native spoken-word recognition under adverse conditions.

Noise Modulates Crosslinguistic Effects on Second-Language Auditory Word Recognition

PURPOSE

This study investigates whether crosslinguistic effects on auditory word recognition are modulated by the quality of the auditory signal (clear and noisy).

METHOD

In an online experiment, a group of Spanish-English bilingual listeners performed an auditory lexical decision task, in their second language, English. Words and pseudowords were either presented in the clear or were embedded in white auditory noise. Target words were varied in the degree to which they overlapped in their phonological form with their translation equivalents and were categorized according to their overlap as cognates (form and meaning) or noncognates (meaning only). In order to test for effects of crosslinguistic competition, the phonological neighborhood density of the targets' translations was also manipulated.

RESULTS

The results show that crosslinguistic effects are impacted by noise; when the translation had a high neighborhood density, performance was worse for cognates than for noncognates, especially in noise.

CONCLUSIONS

The findings suggest that noise increases lexical competition across languages, as it does within a language, and that the crosslinguistic phonological overlap for cognates compared with noncognates can further increase the pool of competitors by co-activating crosslinguistic lexical candidates. The results are discussed within the context of the bilingual word recognition literature and models of language and bilingual lexical processing.