Publications

Abstract

Previous research on the effect of perturbed auditory feedback in speech production has focused on two types of responses. In the short term, speakers generate compensatory motor commands in response to unexpected perturbations. In the longer term, speakers adapt feedforward motor programmes in response to feedback perturbations, to avoid future errors. The current study investigated the relation between these two types of responses to altered auditory feedback. Specifically, it was hypothesised that consistency in previous feedback perturbations would influence whether speakers adapt their feedforward motor programmes. In an altered auditory feedback paradigm, formant perturbations were applied either across all trials (the consistent condition) or only to some trials, whereas the others remained unperturbed (the inconsistent condition). The results showed that speakers’ responses were affected by feedback consistency, with stronger speech changes in the consistent condition compared with the inconsistent condition. Current models of speech-motor control can explain this consistency effect. However, the data also suggest that compensation and adaptation are distinct processes, which are not in line with all current models.

Abstract

This study examined electrophysiological correlates of sentence comprehension of native-accented and foreign-accented
speech in a second language (L2), for sentences produced in a foreign accent different from that associated with the listeners’
L1. Bilingual speaker-listeners process different accents in their L2 conversations, but the effects on real-time L2 sentence
comprehension are unknown. Dutch–English bilinguals listened to native American-English accented sentences and foreign
(and for them unfamiliarly-accented) Chinese-English accented sentences while EEG was recorded. Behavioral sentence
comprehension was highly accurate for both native-accented and foreign-accented sentences. ERPs showed different patterns
for L2 grammar and semantic processing of native- and foreign-accented speech. For grammar, only native-accented speech
elicited an Nref. For semantics, both native- and foreign-accented speech elicited an N400 effect, but with a delayed onset
across both accent conditions. These findings suggest that the way listeners comprehend native- and foreign-accented
sentences in their L2 depends on their familiarity with the accent.

Abstract

Research Findings: The present study compared effects of explicit instruction on and practice with the phonological form of words (form-focused instruction) versus explicit instruction on and practice with the meaning of words (meaning-focused instruction). Instruction was given via interactive storybook reading in the kindergarten classroom of children learning Dutch. We asked whether the 2 types of instruction had different effects on vocabulary development and 2 precursors of reading ability—phonological awareness and letter knowledge—and we examined effects on these measures of the ability to learn new words with minimal acoustic-phonetic differences. Learners showed similar receptive target-word vocabulary gain after both types of instruction, but learners who received form-focused vocabulary instruction showed more gain in semantic knowledge of target vocabulary, phonological awareness, and letter knowledge than learners who received meaning-focused vocabulary instruction. Level of ability to learn pairs of words with minimal acoustic-phonetic differences predicted gain in semantic knowledge of target vocabulary and in letter knowledge in the form-focused instruction group only. Practice or Policy: A focus on the form of words during instruction appears to have benefits for young children learning vocabulary.

Abstract

The field of second language acquisition (SLA) is by nature of its subject a highly interdisciplinary area of research. Learning a (foreign) language, for example, involves encoding new words, consolidating and committing them to long-term memory, and later retrieving them. All of these processes have direct parallels in the domain of human memory and have been thoroughly studied by researchers in that field. Yet, despite these clear links, the two fields have largely developed in parallel and in isolation from one another. The present paper aims to promote more cross-talk between SLA and memory science. We focus on foreign language (FL) attrition as an example of a research topic in SLA where the parallels with memory science are especially apparent. We discuss evidence that suggests that competition between languages is one of the mechanisms of FL attrition, paralleling the interference process thought to underlie forgetting in other domains of human memory. Backed up by concrete suggestions, we advocate the use of paradigms from the memory literature to study these interference effects in the language domain. In doing so, we hope to facilitate future cross-talk between the two fields, and to further our understanding of FL attrition as a memory phenomenon.

Abstract

We tested whether statistical averageness (SA) at the level of the individual speaker could predict a speaker’s intelligibility. 28 female and 21 male speakers of Dutch were recorded producing 336 sentences,
each containing two target nouns. Recordings were compared to those of all other same-sex speakers using dynamic time warping (DTW). For each sentence, the DTW distance constituted a metric
of phonetic distance from one speaker to all other speakers. SA comprised the average of these distances. Later, the same participants performed a word recognition task on the target nouns in the same sentences, under three degraded listening conditions. In all three conditions, accuracy increased with SA. This held even when participants listened to their own utterances. These findings suggest that listeners process speech with respect to the statistical
properties of the language spoken in their community, rather than using their own speech as a reference

Abstract

In language comprehension, a variety of contextual cues act in unison to render upcoming words more or less predictable. As a sentence unfolds, we use prior context (sentential constraints) to predict what the next words might be. Additionally, in a conversation, we can predict upcoming sounds through observing the mouth movements of a speaker (visual constraints). In electrophysiological studies, effects of visual constraints have typically been observed early in language processing, while effects of sentential constraints have typically been observed later. We hypothesized that the visual and the sentential constraints might feed into the same predictive process such that effects of sentential constraints might also be detectable early in language processing through modulations of the early effects of visual salience. We presented participants with audiovisual speech while recording their brain activity with magnetoencephalography. Participants saw videos of a person saying sentences where the last word was either sententially constrained or not, and began with a salient or non-salient mouth movement. We found that sentential constraints indeed exerted an early (N1) influence on language processing. Sentential modulations of the N1 visual predictability effect were visible in brain areas associated with semantic processing, and were differently expressed in the two hemispheres. In the left hemisphere, visual and sentential constraints jointly suppressed the auditory evoked field, while the right hemisphere was sensitive to visual constraints only in the absence of strong sentential constraints. These results suggest that sentential and visual constraints can jointly influence even very early stages of audiovisual speech comprehension.

Abstract

Memory representations of words are thought to undergo changes with consolidation: Episodic memories of novel words are transformed into lexical representations that interact with other words in the mental dictionary. Behavioral studies have shown that this lexical integration process is enhanced when there is more time for consolidation. Neuroimaging studies have further revealed that novel word representations are initially represented in a hippocampally-centered system, whereas left posterior middle temporal cortex activation increases with lexicalization. In this study, we measured behavioral and brain responses to newly-learned words in children. Two groups of Dutch children, aged between 8-10 and 14-16 years, were trained on 30 novel Japanese words depicting novel concepts. Children were tested on word-forms, word-meanings, and the novel words’ influence on existing word processing immediately after training, and again after a week. In line with the adult findings, hippocampal involvement decreased with time. Lexical integration, however, was not observed immediately or after a week, neither behaviorally nor neurally. It appears that time alone is not always sufficient for lexical integration to occur. We suggest that other factors (e.g., the novelty of the concepts and familiarity with the language the words are derived from) might also influence the integration process.

Abstract

In lexical development, the specificity of phonological representations is important. The ability to build phonologically specific lexical representations predicts the number of words a child knows (vocabulary breadth), but it is not clear if it also fosters how well words are known (vocabulary depth). Sixty-six children were studied in kindergarten (age 5;7) and first grade (age 6;8). The predictive value of the ability to learn phonologically similar new words, phoneme discrimination ability, and phonological awareness on vocabulary breadth and depth were assessed using hierarchical regression. Word learning explained unique variance in kindergarten and first-grade vocabulary depth, over the other phonological factors. It did not explain unique variance in vocabulary breadth. Furthermore, even after controlling for kindergarten vocabulary breadth, kindergarten word learning still explained unique variance in first-grade vocabulary depth. Skill in learning phonologically similar words appears to predict knowledge children have about what words mean.

Abstract

This study concerns individual differences in speech imitation ability and the role that lexical representations play in imitation. We examined 1) whether imitation of sounds in an unfamiliar language (L0) is related to imitation of sounds in an unfamiliar
non-native accent in the speaker’s native language (L1) and 2) whether it is easier or harder to imitate speech when you know the words to be imitated. Fifty-nine native Dutch speakers imitated words with target vowels in Basque (/a/ and /e/) and Greekaccented
Dutch (/i/ and /u/). Spectral and durational
analyses of the target vowels revealed no relationship between the success of L0 and L1 imitation and no difference in performance between tasks (i.e., L1
imitation was neither aided nor blocked by lexical knowledge about the correct pronunciation). The results suggest instead that the relationship of the vowels to native phonological categories plays a bigger role in imitation

Abstract

Like many other types of memory formation, novel word learning benefits from an offline consolidation period after the initial encoding phase. A previous EEG study has shown that retrieval of novel words elicited more word-like-induced electrophysiological brain activity in the theta band after consolidation [Bakker, I., Takashima, A., van Hell, J. G., Janzen, G., & McQueen, J. M. Changes in theta and beta oscillations as signatures of novel word consolidation. Journal of Cognitive Neuroscience, 27, 1286–1297, 2015]. This suggests that theta-band oscillations play a role in lexicalization, but it has not been demonstrated that this effect is directly caused by the formation of lexical representations. This study used magnetoencephalography to localize the theta consolidation effect to the left posterior middle temporal gyrus (pMTG), a region known to be involved in lexical storage. Both untrained novel words and words learned immediately before test elicited lower theta power during retrieval than existing words in this region. After a 24-hr consolidation period, the difference between novel and existing words decreased significantly, most strongly in the left pMTG. The magnitude of the decrease after consolidation correlated with an increase in behavioral competition effects between novel words and existing words with similar spelling, reflecting functional integration into the mental lexicon. These results thus provide new evidence that consolidation aids the development of lexical representations mediated by the left pMTG. Theta synchronization may enable lexical access by facilitating the simultaneous activation of distributed semantic, phonological, and orthographic representations that are bound together in the pMTG.

Abstract

This chapter reviews the computational processes that are responsible for recognizing word forms in the speech stream. We outline the different stages in a processing hierarchy from the extraction of general acoustic features, through speech‐specific prelexical processes, to the retrieval and selection of lexical representations. We argue that two recurring properties of the system as a whole are abstraction and adaptability. We also present evidence for parallel processing of information on different timescales, more specifically that segmental material in the speech stream (its consonants and vowels) is processed in parallel with suprasegmental material (the prosodic structures of spoken words). We consider evidence from both psycholinguistics and neurobiology wherever possible, and discuss how the two fields are beginning to address common computational problems. The challenge for future research in speech perception will be to build an account that links these computational problems, through functional mechanisms that address them, to neurobiological implementation.

Abstract

The aim of the present fMRI study was to investigate whether typical and dyslexic adult readers differed in the neural correlates of audiovisual speech processing. We tested for Blood Oxygen-Level Dependent (BOLD) activity differences between these two groups in a 1-back task, as they processed written (word, illegal consonant strings) and spoken (auditory, visual and audiovisual) stimuli. When processing written stimuli, dyslexic readers showed reduced activity in the supramarginal gyrus, a region suggested to play an important role in phonological processing, but only when they processed strings of consonants, not when they read words. During the speech perception tasks, dyslexic readers were only slower than typical readers in their behavioral responses in the visual speech condition. Additionally, dyslexic readers presented reduced neural activation in the auditory, the visual, and the audiovisual speech conditions. The groups also differed in terms of superadditivity, with dyslexic readers showing decreased neural activation in the regions of interest. An additional analysis focusing on vision-related processing during the audiovisual condition showed diminished activation for the dyslexic readers in a fusiform gyrus cluster. Our results thus suggest that there are differences in audiovisual speech processing between dyslexic and normal readers. These differences might be explained by difficulties in processing the unisensory components of audiovisual speech, more specifically, dyslexic readers may benefit less from visual information during audiovisual speech processing than typical readers. Given that visual speech processing supports the development of phonological skills fundamental in reading, differences in processing of visual speech could contribute to differences in reading ability between typical and dyslexic readers.

Abstract

When talking, speakers continuously monitor and use the auditory feedback of their own voice to control and inform speech production processes. When speakers are provided with auditory feedback that is perturbed in real time, most of them compensate for this by opposing the feedback perturbation. But some speakers follow the perturbation. In the current study, we investigated whether the state of the speech production system at perturbation onset may determine what type of response (opposing or following) is given. The results suggest that whether a perturbation-related response is opposing or following depends on ongoing fluctuations of the production system: It initially responds by doing the opposite of what it was doing. This effect and the non-trivial proportion of following responses suggest that current production models are inadequate: They need to account for why responses to unexpected sensory feedback depend on the production-system’s state at the time of perturbation.

Abstract

Speaking is a complex motor skill which requires near instantaneous integration of sensory and motor-related information. Current theory hypothesizes a complex interplay between motor and auditory processes during speech production, involving the online comparison of the speech output with an internally generated forward model. To examine the neural correlates of this intricate interplay between sensory and motor processes, the current study uses altered auditory feedback (AAF) in combination with magnetoencephalography (MEG). Participants vocalized the vowel/e/and heard auditory feedback that was temporarily pitch-shifted by only 25 cents, while neural activity was recorded with MEG. As a control condition, participants also heard the recordings of the same auditory feedback that they heard in the first half of the experiment, now without vocalizing. The participants were not aware of any perturbation of the auditory feedback. We found auditory cortical areas responded more strongly to the pitch shifts during vocalization. In addition, auditory feedback perturbation resulted in spectral power increases in the θ and lower β bands, predominantly in sensorimotor areas. These results are in line with current models of speech production, suggesting auditory cortical areas are involved in an active comparison between a forward model's prediction and the actual sensory input. Subsequently, these areas interact with motor areas to generate a motor response. Furthermore, the results suggest that θ and β power increases support auditory-motor interaction, motor error detection and/or sensory prediction processing.

Abstract

This study investigated whether relative lexical proficiency in Dutch and English in child second language (L2) learners is related to executive functioning. Participants were Dutch primary school pupils of three different age groups (4–5, 8–9, and 11–12 years) who either were enrolled in an early-English schooling program or were age-matched controls not on that early-English program. Participants performed tasks that measured switching, inhibition, and working memory. Early-English program pupils had greater knowledge of English vocabulary and more balanced Dutch–English lexicons. In both groups, lexical balance, a ratio measure obtained by dividing vocabulary scores in English by those in Dutch, was related to switching but not to inhibition or working memory performance. These results show that for children who are learning an L2 in an instructional setting, and for whom managing two languages is not yet an automatized process, language balance may be more important than L2 proficiency in influencing the relation between childhood bilingualism and switching abilities.

Abstract

What are the phonological representations that listeners use to map information about the segmental content of speech onto the mental lexicon during spoken-word recognition? Recent evidence from perceptual-learning paradigms seems to support (context-dependent) allophones as the basic representational units in spoken-word recognition. But recent evidence from a selective-adaptation paradigm seems to suggest that context-independent phonemes also play a role. We present three experiments using selective adaptation that constitute strong tests of these representational hypotheses. In Experiment 1, we tested generalization of selective adaptation using different allophones of Dutch /r/ and /l/ – a case where generalization has not been found with perceptual learning. In Experiments 2 and 3, we tested generalization of selective adaptation using German back fricatives in which allophonic and phonemic identity were varied orthogonally. In all three experiments, selective adaptation was observed only if adaptors and test stimuli shared allophones. Phonemic identity, in contrast, was neither necessary nor sufficient for generalization of selective adaptation to occur. These findings and other recent data using the perceptual-learning paradigm suggest that pre-lexical processing during spoken-word recognition is based on allophones, and not on context-independent phonemes

Abstract

Establishing non-native phoneme categories can be a notoriously difficult endeavour—in both speech perception and speech production. This study asks how these two domains interact in the course of this learning process. It investigates the effect of perceptual learning and related production practice of a challenging non-native category on the perception and/or production of that category. A four-day perceptual training protocol on the British English /æ/-/ɛ/ vowel contrast was combined with either related or unrelated production practice. After feedback on perceptual categorisation of the contrast, native Dutch participants in the related production group (N = 19) pronounced the trial's correct answer, while participants in the unrelated production group (N = 19) pronounced similar but phonologically unrelated words. Comparison of pre- and post-tests showed significant improvement over the course of training in both perception and production, but no differences between the groups were found. The lack of an effect of production practice is discussed in the light of previous, competing results and models of second-language speech perception and production. This study confirms that, even in the context of related production practice, perceptual training boosts production learning.

Abstract

This study examines the influence of orthography on the processing of reduced word forms. For this purpose, we compared the impact of phonological variation with the impact of spelling-sound consistency on the processing of words that may be produced with or without the vowel schwa. Participants learnt novel French words in which the vowel schwa was present or absent in the first syllable. In Experiment 1, the words were consistently produced without schwa or produced in a variable manner (i.e., sometimes produced with and sometimes produced without schwa). In Experiment 2, words were always produced in a consistent manner, but an orthographic exposure phase was included in which words that were produced without schwa were either spelled with or without the letter . Results from naming and eye-tracking tasks suggest that both phonological variation and spelling-sound consistency influence the processing of spoken novel words. However, the influence of phonological variation outweighs the effect of spelling-sound consistency. Our findings therefore suggest that the influence of orthography on the processing of reduced word forms is relatively small.

Abstract

The results of a word-spotting experiment are presented in which Dutch listeners tried to spot different types of bisyllabic Dutch words embedded in different types of nonsense contexts. Embedded verbs were not reliably harder to spot than embedded nouns; this suggests that nouns and verbs are recognised via the same basic processes. Iambic words were no harder to spot than trochaic words, suggesting that trochaic words are not in principle easier to recognise than iambic words. Words were harder to spot in consonantal contexts (i.e., contexts which themselves could not be words) than in longer contexts which contained at least one vowel (i.e., contexts which, though not words, were possible words of Dutch). A control experiment showed that this difference was not due to acoustic differences between the words in each context. The results support the claim that spoken-word recognition is sensitive to the viability of sound sequences as possible words.