Publications

Abstract

We utilized the N400 effect to investigate the influence of speech register on predictive language processing. Participants listened to long stretches (4 – 15 min) of naturalistic speech from different registers (dialogues, news broadcasts, and read-aloud books), totalling approximately 50,000 words, while the EEG signal was recorded. We estimated the surprisal of words in the speech materials with the aid of a statistical language model in such a manner that it reflected different predictive processing strategies; generic, register-specific, or recency-based. The N400 amplitude was best predicted with register-specific word surprisal, indicating that the statistics of the wider context (i.e., register) influences predictive language processing. Furthermore, adaptation to speech register cannot merely be explained by recency effects; instead, listeners adapt their word anticipations to the presented speech register.

Abstract

We present a dataset of behavioural and fMRI observations acquired in the context of humans involved in multimodal referential communication. The dataset contains audio/video and motion-tracking recordings of face-to-face, task-based communicative interactions in Dutch, as well as behavioural and neural correlates of participants’ representations of dialogue referents. Seventy-one pairs of unacquainted participants performed two interleaved interactional tasks in which they described and located 16 novel geometrical objects (i.e., Fribbles) yielding spontaneous interactions of about one hour. We share high-quality video (from three cameras), audio (from head-mounted microphones), and motion-tracking (Kinect) data, as well as speech transcripts of the interactions. Before and after engaging in the face-to-face communicative interactions, participants’ individual representations of the 16 Fribbles were estimated. Behaviourally, participants provided a written description (one to three words) for each Fribble and positioned them along 29 independent conceptual dimensions (e.g., rounded, human, audible). Neurally, fMRI signal evoked by each Fribble was measured during a one-back working-memory task. To enable functional hyperalignment across participants, the dataset also includes fMRI measurements obtained during visual presentation of eight animated movies (35 minutes total). We present analyses for the various types of data demonstrating their quality and consistency with earlier research. Besides high-resolution multimodal interactional data, this dataset includes different correlates of communicative referents, obtained before and after face-to-face dialogue, allowing for novel investigations into the relation between communicative behaviours and the representational space shared by communicators. This unique combination of data can be used for research in neuroscience, psychology, linguistics, and beyond.

Abstract

Speech produced in noise (Lombard speech) is more intelligible than speech produced in quiet (plain speech). Previous research on the Lombard intelligibility benefit focused almost entirely on how native speakers produce and perceive Lombard speech. In this study, we investigate the size of the Lombard intelligibility benefit of both native (American-English) and non-native (native Dutch) English for native and non-native listeners (Dutch and Spanish). We used a glimpsing metric to measure the energetic masking potential of speech, which predicted that both native and non-native Lombard speech could withstand greater amounts of masking to a similar extent, compared to plain speech. In an intelligibility experiment, native English, Spanish, and Dutch listeners listened to the same words, mixed with noise. While the non-native listeners appeared to benefit more from Lombard speech than the native listeners did, each listener group experienced a similar benefit for native and non-native Lombard speech. Energetic masking, as captured by the glimpsing metric, only accounted for part of the Lombard benefit, indicating that the Lombard intelligibility benefit does not only result from a shift in spectral distribution. Despite subtle native language influences on non-native Lombard speech, both native and non-native speech provides a Lombard benefit.

Abstract

Distributional semantic models capture word-level meaning that is useful in many natural language processing tasks and have even been shown to capture cognitive aspects of word meaning. The majority of these models are purely text based, even though the human sensory experience is much richer. In this paper we create visually grounded word embeddings by combining English text and images and compare them to popular text-based methods, to see if visual information allows our model to better capture cognitive aspects of word meaning. Our analysis shows that visually grounded embedding similarities are more predictive of the human reaction times in a large priming experiment than the purely text-based embeddings. The visually grounded embeddings also correlate well with human word similarity ratings.Importantly, in both experiments we show that he grounded embeddings account for a unique portion of explained variance, even when we include text-based embeddings trained on huge corpora. This shows that visual grounding allows our model to capture information that cannot be extracted using text as the only source of information.

Abstract

This study compares the role of exemplars in native and non-native listening. Two English identity priming experiments were conducted with native English, Dutch non-native, and Spanish non-native listeners. In Experiment 1, primes and targets were spoken in the same or a different voice. Only the native listeners showed exemplar effects. In Experiment 2, primes and targets had the same or a different degree of vowel reduction. The Dutch, but not the Spanish, listeners were familiar with this reduction pattern from their L1 phonology. In this experiment, exemplar effects only arose for the Spanish listeners. We propose that in these lexical decision experiments the use of exemplars is co-determined by listeners’ available processing resources, which is modulated by the familiarity with the variation type from their L1 phonology. The use of exemplars differs between native and non-native listening, suggesting qualitative differences between native and non-native speech comprehension processes.

Abstract

This study investigated pronunciation variants of word-final obstruent-liquid-schwa (OLS) clusters in casual French and the variables predicting the absence of the phonemes in these clusters. In a dataset of 291 noun tokens extracted from a corpus of casual conversations, we observed that in 80.7% of the tokens, at least one phoneme was absent and that in no less than 15.5% the whole cluster was absent (e.g., /mis/ for ministre). Importantly, the probability of a phoneme being absent was higher if the following phoneme was absent as well. These data show that reduction can affect several phonemes at once and is not restricted to just a handful of (function) words. Moreover, our results demonstrate that the absence of each single phoneme is affected by the speaker's tendency to increase ease of articulation and to adapt a word's pronunciation variant to the time available.

Abstract

The present study investigated the effect of orthography on the learning and subsequent processing of pronunciation variants in a second language. Dutch learners of French learned reduced pronunciation variants that result from schwa-zero alternation in French (e.g., reduced /ʃnij/ from chenille 'caterpillar'). Half of the participants additionally learnt the words' spellings, which correspond more closely to the full variants with schwa. On the following day, participants performed an auditory lexical decision task, in which they heard half of the words in their reduced variants, and the other half in their full variants. Participants who had exclusively learnt the auditory forms performed significantly worse on full variants than participants who had also learnt the spellings. This shows that learners integrate phonological and orthographic information to process pronunciation variants. There was no difference between both groups in their performances on reduced variants, suggesting that the exposure to spelling does not impede learners' processing of these variants.

Abstract

In an auditory lexical decision experiment, 5,541 spoken content words and pseudo-words were presented to 20 native speakers of Dutch. The words vary in phonological makeup and in number of syllables and stress pattern, and are further representative of the native Dutch vocabulary in that most are morphologically complex, comprising two stems or one stem plus derivational and inflectional suffixes, with inflections representing both regular and irregular paradigms; the pseudo-words were matched in these respects to the real words. The BALDEY data file includes response times and accuracy rates, with for each item morphological information plus phonological and acoustic information derived from automatic phonemic segmentation of the stimuli. Two initial analyses illustrate how this data set can be used. First, we discuss several measures of the point at which a word has no further neighbors, and compare the degree to which each measure predicts our lexical decision response outcomes. Second, we investigate how well four different measures of frequency of occurrence (from written corpora, spoken corpora, subtitles and frequency ratings by 70 participants) predict the same outcomes. These analyses motivate general conclusions about the auditory lexical decision task. The (publicly available) BALDEY database lends itself to many further analyses.

Abstract

This article presents two studies investigating how the situation in which speech is uttered affects the frequency with which words are reduced. Study 1 is based on the Spoken Dutch Corpus, which consists of 15 components, nearly all representing a different speech situation. This study shows that the components differ in how often ten semantically weak words are highly reduced. The differences are especially large between the components with scripted and unscripted speech. Within the component group of unscripted speech, the formality of the situation shows an effect. Study 2 investigated segment reduction in a shadowing experiment in which participants repeated Dutch carefully and casually articulated sentences. Prefixal schwa and suffixal /t/ were absent in participants' responses to both sentences types as often as in formal interviews. If a segment was absent, this appeared to be mostly due to extreme co-articulation, unlike in speech produced in less formal situations. Speakers thus adapted more to the formal situation of the experiment than to the stimuli to be shadowed. We conclude that speech situation affects the occurrence of reduced word pronunciation variants, which should be accounted for by psycholinguistic models of speech production and comprehension

Abstract

This paper investigates whether individual speakers forming a homogeneous group differ in their choice and pronunciation of words when engaged in casual conversation, and if so, how they differ. More specifically, it examines whether the Balanced Winnow classifier is able to distinguish between the twenty speakers of the Ernestus Corpus of Spontaneous Dutch, who all have the same social background. To examine differences in choice and pronunciation of words, instead of characteristics of the speech signal itself, classification was based on lexical and pronunciation features extracted from hand-made orthographic and automatically generated broad phonetic transcriptions. The lexical features consisted of words and two-word combinations. The pronunciation features represented pronunciation variations at the word and phone level that are typical for casual speech. The best classifier achieved a performance of 79.9% and was based on the lexical features and on the pronunciation features representing single phones and triphones. The speakers must thus differ from each other in these features. Inspection of the relevant features indicated that, among other things, the words relevant for classification generally do not contain much semantic content, and that speakers differ not only from each other in the use of these words but also in their pronunciation.

Abstract

This paper studies the robustness of exemplar effects in word comprehension by means of four long-term priming experiments with lexical decision tasks in Dutch. A prime and target represented the same word type and were presented with the same or different degree of reduction. In Experiment 1, participants heard only a small number of trials, a large proportion of repeated words, and stimuli produced by only one speaker. They recognized targets more quickly if these represented the same degree of reduction as their primes, which forms additional evidence for the exemplar effects reported in the literature. Similar effects were found for two speakers who differ in their pronunciations. In Experiment 2, with a smaller proportion of repeated words and more trials between prime and target, participants recognized targets preceded by primes with the same or a different degree of reduction equally quickly. Also, in Experiments 3 and 4, in which listeners were not exposed to one but two types of pronunciation variation (reduction degree and speaker voice), no exemplar effects arose. We conclude that the role of exemplars in speech comprehension during natural conversations, which typically involve several speakers and few repeated content words, may be smaller than previously assumed.

Abstract

This paper investigated the learnability and generalizability of French schwa alternation by Dutch low-proficiency second language learners. We trained 40 participants on 24 new schwa words by exposing them equally often to the reduced and full forms of these words. We then assessed participants' accuracy and reaction times to these newly learnt words as well as 24 previously encountered schwa words with an auditory lexical decision task. Our results show learning of the new words in both forms. This suggests that lack of exposure is probably the main cause of learners' difficulties with reduced forms. Nevertheless, the full forms were slightly better recognized than the reduced ones, possibly due to phonetic and phonological properties of the reduced forms. We also observed no generalization to previously encountered words, suggesting that our participants stored both of the learnt word forms and did not create a rule that applies to all schwa words.

Abstract

In speech, words are often reduced rather than fully pronounced (e.g., (/ˈsʌmri/ for /ˈsʌməri/, summary). Non-native listeners may have problems in processing these reduced forms, because they have encountered them less often. This paper addresses the question whether this also holds for highly proficient non-natives and for words with similar forms and meanings in the non-natives' mother tongue (i.e., cognates). In an English auditory lexical decision task, natives and highly proficient Dutch non-natives of English listened to cognates and non-cognates that were presented in full or without their post-stress schwa. The data show that highly proficient learners are affected by reduction as much as native speakers. Nevertheless, the two listener groups appear to process reduced forms differently, because non-natives produce more errors on reduced cognates than on non-cognates. While listening to reduced forms, non-natives appear to be hindered by the co-activated lexical representations of cognate forms in their native language.

Abstract

This paper studies the influence of adverse listening conditions on exemplar effects in priming experiments that do not instruct participants to use their episodic memories. We conducted two lexical decision experiments, in which a prime and a target represented the same word type and could be spoken by the same or a different speaker. In Experiment 1, participants listened to clear speech, and showed no exemplar effects: they recognised repetitions by the same speaker as quickly as different speaker repetitions. In Experiment 2, the stimuli contained noise, and exemplar effects did arise. Importantly, Experiment 1 elicited longer average RTs than Experiment 2, a result that contradicts the time-course hypothesis, according to which exemplars only play a role when processing is slow. Instead, our findings support the hypothesis that exemplar effects arise under adverse listening conditions, when participants are stimulated to use their episodic memories in addition to their mental lexicons.

Abstract

This paper presents DIANA, a new computational model of human speech processing. It is the first model that simulates the complete processing chain from the on-line processing of an acoustic signal to the execution of a response, including reaction times. Moreover it assumes minimal modularity. DIANA consists of three components. The activation component computes a probabilistic match between the input acoustic signal and representations in DIANA’s lexicon, resulting in a list of word hypotheses changing over time as the input unfolds. The decision component operates on this list and selects a word as soon as sufficient evidence is available. Finally, the execution component accounts for the time to execute a behavioral action. We show that DIANA well simulates the average participant in a word recognition experiment.

Abstract

DIANA is an end-to-end computational model of speech processing, which takes as input the speech signal, and provides as output the orthographic transcription of the stimulus, a word/non-word judgment and the associated estimated reaction time. So far, the model has only been tested for Dutch. In this paper, we extend DIANA such that it can also process North American English. The model is tested by having it simulate human participants in a large scale North American English lexical decision experiment. The simulations show that DIANA can adequately approximate the reaction times of an average participant (r = 0.45). In addition, they indicate that DIANA does not yet adequately model the cognitive processes that take place after stimulus offset.

Abstract

Acoustic reduction refers to the frequent phenomenon in conversational speech that words are produced with fewer or lenited segments compared to their citation forms. The few published studies on the production and comprehension of acoustic reduction have important implications for the debate on the relevance of abstractions and exemplars in speech processing. This article discusses these implications. It first briefly introduces the key assumptions of simple abstractionist and simple exemplar-based models. It then discusses the literature on acoustic reduction and draws the conclusion that both types of models need to be extended to explain all findings. The ultimate model should allow for the storage of different pronunciation variants, but also reserve an important role for phonetic implementation. Furthermore, the recognition of a highly reduced pronunciation variant requires top down information and leads to activation of the corresponding unreduced variant, the variant that reaches listeners’ consciousness. These findings are best accounted for in hybrids models, assuming both abstract representations and exemplars. None of the hybrid models formulated so far can account for all data on reduced speech and we need further research for obtaining detailed insight into how speakers produce and listeners comprehend reduced speech.

Abstract

This article introduces a new speech corpus, the Nijmegen Corpus of Casual Czech (NCCCz), which contains more than 30 hours of high-quality recordings of casual conversations in Common Czech, among ten groups of three male and ten groups of three female friends. All speakers were native speakers of Czech, raised in Prague or in the region of Central Bohemia, and were between 19 and 26 years old. Every group of speakers consisted of one confederate, who was instructed to keep the conversations lively, and two speakers naive to the purposes of the recordings. The naive speakers were engaged in conversations for approximately 90 minutes, while the confederate joined them for approximately the last 72 minutes. The corpus was orthographically annotated by experienced transcribers and this orthographic transcription was aligned with the speech signal. In addition, the conversations were videotaped. This corpus can form the basis for all types of research on casual conversations in Czech, including phonetic research and research on how to improve automatic speech recognition. The corpus will be freely available

Abstract

In spontaneous conversations between adults, words are often pronounced with fewer segments or syllables than their citation forms. The question arises whether infant-directed speech also contains phonetic reduction. If so, infants would be presented with speech input that enables them to acquire reduced variants from an early age. This study compared speech directed at 11- and 12-month-old infants with adult-directed conversational speech and adult-directed read speech. In an acoustic study, 216 tokens of the Dutch words allemaal and helemaal from speech corpora were analyzed for duration, number of syllables, and vowel quality. In a perception study, adult participants rated these same materials for reduction and provided phonetic transcriptions. The results show that these two words are frequently reduced in infant-directed speech, and that their degree of reduction is comparable with conversational adult-directed speech. These findings suggest that lexical representations for reduced pronunciation variants can be acquired early in linguistic development

Abstract

This paper describes the pilot study of phonetic segmentation applied to Nijmegen Corpus of Casual Czech (NCCCz). This corpus contains informal speech of strong spontaneous nature which influences the character of produced speech at various levels. This work is the part of wider research related to the analysis of pronunciation reduction in such informal speech. We present the analysis of the accuracy of phonetic segmentation when canonical or reduced pronunciation is used. The achieved accuracy of realized phonetic segmentation provides information about general accuracy of proper acoustic modelling which is supposed to be applied in spontaneous speech recognition. As a byproduct of presented spontaneous speech segmentation, this paper also describes the created lexicon with canonical pronunciations of words in NCCCz, a tool supporting pronunciation check of lexicon items, and finally also a minidatabase of selected utterances from NCCCz manually labelled on phonetic level suitable for evaluation purposes

Abstract

This study examines how lexical frequency and planning problems can predict phonetic variability in the function word ‘the’ in conversational speech produced by non-native speakers of English. We examined 3180 tokens of ‘the’ drawn from English conversations between native speakers of Czech or Norwegian. Using regression models, we investigated the effect of following word frequency and disfluencies on three phonetic parameters: vowel duration, vowel quality, and consonant quality. Overall, the non-native speakers showed variation that is very similar to the variation displayed by native speakers of English. Like native speakers, Czech speakers showed an effect of frequency on vowel durations, which were shorter in more frequent word sequences. Both groups of speakers showed an effect of frequency on consonant quality: the substitution of another consonant for /ð/ occurred more often in the context of more frequent words. The speakers in this study also showed a native-like allophonic distinction in vowel quality, in which /ði/ occurs more often before vowels and /ðə/ before consonants. Vowel durations were longer in the presence of following disfluencies, again mirroring patterns in native speakers, and the consonant quality was more likely to be the target /ð/ before disfluencies, as opposed to a different consonant. The fact that non-native speakers show native-like sensitivity to lexical frequency and disfluencies suggests that these effects are consequences of a general, non-language-specific production mechanism governing language planning. On the other hand, the non-native speakers in this study did not show native-like patterns of vowel quality in the presence of disfluencies, suggesting that the pattern attested in native speakers of English may result from language-specific processes separate from the general production mechanisms

Abstract

This paper addresses the question how to compare reaction times computed by a computational model of speech comprehension with observed reaction times by participants. The question is based on the observation that reaction time sequences substantially differ per participant, which raises the issue of how exactly the model is to be assessed. Part of the variation in reaction time sequences is caused by the so-called local speed: the current reaction time correlates to some extent with a number of previous reaction times, due to slowly varying variations in attention, fatigue etc. This paper proposes a method, based on time series analysis, to filter the observed reaction times in order to separate the local speed effects. Results show that after such filtering the between-participant correlations increase as well as the average correlation between participant and model increases. The presented technique provides insights into relevant aspects that are to be taken into account when comparing reaction time sequences