Publications

Abstract

Speech-in-speech perception can be challenging because the processing of competing acoustic and linguistic information leads to informational masking. Here, a method is proposed to isolate the linguistic component of informational masking while keeping the distractor's acoustic information unchanged. Participants performed a dichotic listening cocktail-party task before and after training on 4-band noise-vocoded sentences that became intelligible through the training. Distracting noise-vocoded speech interfered more with target speech comprehension after training (i.e., when intelligible) than before training (i.e., when unintelligible) at −3 dB SNR. These findings confirm that linguistic and acoustic information have distinct masking effects during speech-in‐speech comprehension

Abstract

The aim of this study was to clarify whether audiovisual processing accounted for variance in reading and reading-related abilities, beyond the effect of a set of measures typically associated with individual differences in both reading and audiovisual processing. Testing adults with and without a diagnosis of dyslexia, we showed that—across all participants, and after accounting for variance in cognitive abilities—audiovisual temporal sensitivity contributed uniquely to variance in reading errors. This is consistent with previous studies demonstrating an audiovisual deficit in dyslexia. Additionally, we showed that speechreading (identification of speech based on visual cues from the talking face alone) was a unique contributor to variance in phonological awareness in dyslexic readers only: those who scored higher on speechreading, scored lower on phonological awareness. This suggests a greater reliance on visual speech as a compensatory mechanism when processing auditory speech is problematic. A secondary aim of this study was to better understand the nature of dyslexia. The finding that a sub-group of dyslexic readers scored low on phonological awareness and high on speechreading is consistent with a hybrid perspective of dyslexia: There are multiple possible pathways to reading impairment, which may translate into multiple profiles of dyslexia.

Abstract

Purpose: Because reading is an audiovisual process, reading impairment may reflect an audiovisual processing deficit. The aim of the present study was to test the existence and scope of such a deficit in adult readers with dyslexia. Method: We tested 39 typical readers and 51 adult readers with dyslexia on their sensitivity to the simultaneity of audiovisual speech and nonspeech stimuli, their time window of audiovisual integration for speech (using incongruent /aCa/ syllables), and their audiovisual perception of phonetic categories. Results: Adult readers with dyslexia showed less sensitivity to audiovisual simultaneity than typical readers for both speech and nonspeech events. We found no differences between readers with dyslexia and typical readers in the temporal window of integration for audiovisual speech or in the audiovisual perception of phonetic categories. Conclusions: The results suggest an audiovisual temporal deficit in dyslexia that is not specific to speech-related events. But the differences found for audiovisual temporal sensitivity did not translate into a deficit in audiovisual speech perception. Hence, there seems to be a hiatus between simultaneity judgment and perception, suggesting a multisensory system that uses different mechanisms across tasks. Alternatively, it is possible that the audiovisual deficit in dyslexia is only observable when explicit judgments about audiovisual simultaneity are required

Abstract

One of the most daunting tasks of a listener is to map a
continuous auditory stream onto known speech sound
categories and lexical items. A major issue with this mapping
problem is the variability in the acoustic realizations of sound
categories, both within and across speakers. Past research has
suggested listeners may use visual information (e.g., lipreading)
to calibrate these speech categories to the current
speaker. Previous studies have focused on audiovisual
recalibration of consonant categories. The present study
explores whether vowel categorization, which is known to show
less sharply defined category boundaries, also benefit from
visual cues.
Participants were exposed to videos of a speaker
pronouncing one out of two vowels, paired with audio that was
ambiguous between the two vowels. After exposure, it was
found that participants had recalibrated their vowel categories.
In addition, individual variability in audiovisual recalibration is
discussed. It is suggested that listeners’ category sharpness may
be related to the weight they assign to visual information in
audiovisual speech perception. Specifically, listeners with less
sharp categories assign more weight to visual information
during audiovisual speech recognition.

Abstract

An important part of understanding speech motor control consists of capturing the
interaction between speech production and speech perception. This study tests a
prediction of theoretical frameworks that have tried to account for these interactions: if
speech production targets are specified in auditory terms, individuals with better
auditory acuity should have more precise speech targets, evidenced by decreased
within-phoneme variability and increased between-phoneme distance. A study was
carried out consisting of perception and production tasks in counterbalanced order.
Auditory acuity was assessed using an adaptive speech discrimination task, while
production variability was determined using a pseudo-word reading task. Analyses of
the production data were carried out to quantify average within-phoneme variability as
well as average between-phoneme contrasts. Results show that individuals not only
vary in their production and perceptual abilities, but that better discriminators have
more distinctive vowel production targets (that is, targets with less within-phoneme
variability and greater between-phoneme distances), confirming the initial hypothesis.
This association between speech production and perception did not depend on local
phoneme density in vowel space. This study suggests that better auditory acuity leads
to more precise speech production targets, which may be a consequence of auditory
feedback affecting speech production over time.

Abstract

Children's abilities to process the phonological structure of words are important predictors of their literacy development. In the current study, we examined the interrelatedness between implicit (i.e., speech decoding) and explicit (i.e., phonological awareness) phonological abilities, and especially the role therein of lexical specificity (i.e., the ability to learn to recognize spoken words based on only minimal acoustic-phonetic differences). We tested 75 Dutch monolingual and 64 Turkish–Dutch bilingual kindergartners. SEM analyses showed that speech decoding predicted lexical specificity, which in turn predicted rhyme awareness in the first language learners but phoneme awareness in the second language learners. Moreover, in the latter group there was an impact of the second language: Dutch speech decoding and lexical specificity predicted Turkish phonological awareness, which in turn predicted Dutch phonological awareness. We conclude that language-specific phonological characteristics underlie different patterns of transfer from implicit to explicit phonological abilities in first and second language learners.

Abstract

The acoustic realization of speech is constrained by the physical mechanisms by which it is produced. Yet for speech perception, the degree to which listeners utilize experience derived from speech production has long been debated. In the present study, we examined how sensorimotor adaptation during production may affect perception, and how this relationship may be reflected in early vs. late electrophysiological responses. Participants first performed a baseline speech production task, followed by a vowel categorization task during which EEG responses were recorded. In a subsequent speech production task, half the participants received shifted auditory feedback, leading most to alter their articulations. This was followed by a second, post-training vowel categorization task. We compared changes in vowel production to both behavioral and electrophysiological changes in vowel perception. No differences in phonetic categorization were observed between groups receiving altered or unaltered feedback. However, exploratory analyses revealed correlations between vocal motor behavior and phonetic categorization. EEG analyses revealed correlations between vocal motor behavior and cortical responses in both early and late time windows. These results suggest that participants' recent production behavior influenced subsequent vowel perception. We suggest that the change in perception can be best characterized as a mapping of acoustics onto articulation

Abstract

A given speech sound will be realized differently depending on the context in which it is produced. Listeners have been found to compensate perceptually for these coarticulatory effects, yet it is unclear to what extent this effect depends on actual production experience. In this study, whether changes in motor-to-sound mappings induced by adaptation to altered auditory feedback can affect perceptual compensation for coarticulation is investigated. Specifically, whether altering how the vowel [i] is produced can affect the categorization of a stimulus continuum between an alveolar and a palatal fricative whose interpretation is dependent on vocalic context is tested. It was found that participants could be sorted into three groups based on whether they tended to oppose the direction of the shifted auditory feedback, to follow it, or a mixture of the two, and that these articulatory responses, not the shifted feedback the participants heard, correlated with changes in perception. These results indicate that sensorimotor adaptation to altered feedback can affect the perception of unaltered yet coarticulatorily-dependent speech sounds, suggesting a modulatory role of sensorimotor experience on speech perception

Abstract

When a novel word is learned, its memory representation is thought to undergo a process of consolidation and integration. In this study, we tested whether the neural representations of novel words change as a function of consolidation by observing brain activation patterns just after learning and again after a delay of one week. Words learned with meanings were remembered better than those learned without meanings. Both episodic (hippocampus-dependent) and semantic (dependent on distributed neocortical areas) memory systems were utilised during recognition of the novel words. The extent to which the two systems were involved changed as a function of time and the amount of associated information, with more involvement of both systems for the meaningful words than for the form-only words after the one-week delay. These results suggest that the reason the meaningful words were remembered better is that their retrieval can benefit more from these two complementary memory systems

Abstract

A major goal in the early years of elementary school is learning to read, a process in which children show substantial individual differences. To shed light on the underlying processes of early literacy, this study investigates the interrelations among four known precursors to literacy: phonological short-term memory, vocabulary size, rhyme awareness, and trainability in the phonological specificity of lexical representations, by means of structural equation modelling, in a group of 101 4-year-old children. Trainability in lexical specificity was assessed by teaching children pairs of new phonologically-similar words. Standardized tests of receptive vocabulary, short-term memory, and rhyme awareness were used. The best-fitting model showed that trainability in lexical specificity partially mediated between short-term memory and both vocabulary size and rhyme awareness. These results demonstrate that individual differences in the ability to learn phonologically-similar new words are related to individual differences in vocabulary size and rhyme awareness.

Abstract

This electrophysiological study asked whether the brain processes grammatical gender
violations in casual speech differently than in careful speech. Native speakers of Dutch were
presented with utterances that contained adjective-noun pairs in which the adjective was either
correctly inflected with a word-final schwa (e.g. een spannende roman “a suspenseful novel”) or
incorrectly uninflected without that schwa (een spannend roman). Consistent with previous
findings, the uninflected adjectives elicited an electrical brain response sensitive to syntactic
violations when the talker was speaking in a careful manner. When the talker was speaking in a
casual manner, this response was absent. A control condition showed electrophysiological responses
for carefully as well as casually produced utterances with semantic anomalies, showing that
listeners were able to understand the content of both types of utterance. The results suggest that
listeners take information about the speaking style of a talker into account when processing the
acoustic-phonetic information provided by the speech signal. Absent schwas in casual speech are
effectively not grammatical gender violations. These changes in syntactic processing are evidence
of contextually-driven neural flexibility.

Abstract

We investigated neural mechanisms that support voice recognition in a training paradigm with fMRI. The same listeners were trained on different weeks to categorize the mid-regions of voice-morph continua as an individual's voice. Stimuli implicitly defined a voice-acoustics space, and training explicitly defined a voice-identity space. The predefined centre of the voice category was shifted from the acoustic centre each week in opposite directions, so the same stimuli had different training histories on different tests. Cortical sensitivity to voice similarity appeared over different time-scales and at different representational stages. First, there were short-term adaptation effects: Increasing acoustic similarity to the directly preceding stimulus led to haemodynamic response reduction in the middle/posterior STS and in right ventrolateral prefrontal regions. Second, there were longer-term effects: Response reduction was found in the orbital/insular cortex for stimuli that were most versus least similar to the acoustic mean of all preceding stimuli, and, in the anterior temporal pole, the deep posterior STS and the amygdala, for stimuli that were most versus least similar to the trained voice-identity category mean. These findings are interpreted as effects of neural sharpening of long-term stored typical acoustic and category-internal values. The analyses also reveal anatomically separable voice representations: one in a voice-acoustics space and one in a voice-identity space. Voice-identity representations flexibly followed the trained identity shift, and listeners with a greater identity effect were more accurate at recognizing familiar voices. Voice recognition is thus supported by neural voice spaces that are organized around flexible ‘mean voice’ representations.

Abstract

The possible-word constraint (PWC; Norris, McQueen, Cutler, & Butterfield, 1997) has been proposed as a language-universal segmentation principle: Lexical candidates are disfavoured if the resulting segmentation of continuous speech leads to vowelless residues in the input—for example, single consonants. Three word-spotting experiments investigated segmentation in Slovak, a language with single-consonant words and fixed stress. In Experiment 1, Slovak listeners detected real words such as ruka “hand” embedded in prepositional-consonant contexts (e.g., /gruka/) faster than those in nonprepositional-consonant contexts (e.g., /truka/) and slowest in syllable contexts (e.g., /dugruka/). The second experiment controlled for effects of stress. Responses were still fastest in prepositional-consonant contexts, but were now slowest in nonprepositional-consonant contexts. In Experiment 3, the lexical and syllabic status of the contexts was manipulated. Responses were again slowest in nonprepositional-consonant contexts but equally fast in prepositional-consonant, prepositional-vowel, and nonprepositional-vowel contexts. These results suggest that Slovak listeners use fixed stress and the PWC to segment speech, but that single consonants that can be words have a special status in Slovak segmentation. Knowledge about what constitutes a phonologically acceptable word in a given language therefore determines whether vowelless stretches of speech are or are not treated as acceptable parts of the lexical parse.

Abstract

Signed languages are articulated through simultaneous upper-body movements and are seen; spoken languages are articulated through sequential vocal-tract movements and are heard. But word recognition in both language modalities entails segmentation of a continuous input into discrete lexical units. According to the Possible Word Constraint (PWC), listeners segment speech so as to avoid impossible words in the input. We argue here that the PWC is a modality-general principle. Deaf signers of British Sign Language (BSL) spotted real BSL signs embedded in nonsense-sign contexts more easily when the nonsense signs were possible BSL signs than when they were not. A control experiment showed that there were no articulatory differences between the different contexts. A second control experiment on segmentation in spoken Dutch strengthened the claim that the main BSL result likely reflects the operation of a lexical-viability constraint. It appears that signed and spoken languages, in spite of radical input differences, are segmented so as to leave no residues of the input that cannot be words.

Abstract

Japanese listeners detected Japanese words embedded at the end of nonsense sequences (e.g., kaba 'hippopotamus' in gyachikaba). When the final portion of the preceding context together with the initial portion of the word (e.g., here, the sequence chika) was compatible with many lexical competitors, recognition of the embedded word was more difficult than when such a sequence was compatible with few competitors. This clear effect of competition, established here for preceding context in Japanese, joins similar demonstrations, in other languages and for following contexts, to underline that the functional architecture of the human spoken-word recognition system is a universal one.

Abstract

For optimal word recognition listeners should use all relevant acoustic information as soon as it comes available. Using printed-word eye-tracking we investigated when during word processing Dutch listeners use suprasegmental lexical stress information to recognize words. Fixations on targets such as 'OCtopus' (capitals indicate stress) were more frequent than fixations on segmentally overlapping but differently stressed competitors ('okTOber') before segmental information could disambiguate the words. Furthermore, prior to segmental disambiguation, initially stressed words were stronger lexical competitors than non-initially stressed words. Listeners recognize words by immediately using all relevant information in the speech signal.

Abstract

Four cross-modal repetition priming experiments examined whether consonant duration in Italian provides listeners with information not only for segmental identification ("what" information: whether the consonant is a geminate or a singleton) but also for lexical segmentation (“where” information: whether the consonant is in word-initial or word-medial position). Italian participants made visual lexical decisions to words containing geminates or singletons, preceded by spoken primes (whole words or fragments) containing either geminates or singletons. There were effects of segmental identity (geminates primed geminate recognition; singletons primed singleton recognition), and effects of consonant position (regression analyses revealed graded effects of geminate duration only for geminates which can vary in position, and mixed-effect modeling revealed a positional effect for singletons only in low-frequency words). Durational information appeared to be more important for segmental identification than for lexical segmentation. These findings nevertheless indicate that the same kind of information can serve both "what" and "where" functions in speech comprehension, and that the perceptual processes underlying those functions are interdependent.

Abstract

In foreign-accented speech, listeners have to handle noticeable deviations from the standard pronunciation of a target language. Three cross-modal priming experiments investigated how short- and long-term experiences with a foreign accent influence word recognition by native listeners. In experiment 1, German-accented words were presented to Dutch listeners who had either extensive or limited prior experience with German-accented Dutch. Accented words either contained a diphthong substitution that deviated acoustically quite largely from the canonical form (huis [hys], "house", pronounced as [hoys]), or that deviated acoustically to a lesser extent (lijst [lst], "list", pronounced as [lst]). The mispronunciations never created lexical ambiguity in Dutch. While long-term experience facilitated word recognition for both types of substitutions, limited experience facilitated recognition only of words with acoustically smaller deviations. In experiment 2, Dutch listeners with limited experience listened to the German speaker for 4 min before participating in the cross-modal priming experiment. The results showed that speaker-specific learning effects for acoustically large deviations can be obtained already after a brief exposure, as long as the exposure contains evidence of the deviations. Experiment 3 investigates whether these short-term adaptation effects for foreign-accented speech are speaker-independent.

Abstract

This study aimed first to determine whether there is a delay associated with processing words in an unfamiliar regional accent compared to words in a familiar regional accent, and second to establish whether short-term exposure to an unfamiliar accent affects the speed and accuracy of comprehension of words spoken in that accent. Listeners performed an animacy decision task for words spoken in their own and in an unfamiliar accent. Next, they were exposed to approximately 20 minutes of speech in one of these two accents. After exposure, they repeated the animacy decision task. Results showed a considerable delay in word processing for the unfamiliar accent, but no effect of short-term exposure.

Abstract

We present results from an experiment which shows that voice perception is influenced by the phonetic content of speech. Dutch listeners were presented with thirteen speakers pronouncing CVC words with systematically varying segmental content, and they had to discriminate the speakers’ voices. Results show that certain segments help listeners discriminate voices more than other segments do. Voice information can be extracted from every segmental position of a monosyllabic word and is processed rapidly. We also show that although relative discriminability within a closed set of voices appears to be a stable property of a voice, it is also influenced by segmental cues – that is, perceived uniqueness of a voice depends on what that voice says.

Abstract

We explore the role of the acoustic consequences of domain-initial strengthening in spoken-word recognition. In two cross-modal identity-priming experiments, listeners heard sentences and made lexical decisions to visual targets, presented at the onset of the second word in two-word sequences containing lexical ambiguities (e.g., bus tickets, with the competitor bust). These sequences contained Intonational Phrase (IP) or Prosodic Word (Wd) boundaries, and the second word's initial Consonant and Vowel (CV, e.g., [tI]) was spliced from another token of the sequence in IP- or Wd-initial position. Acoustic analyses showed that IP-initial consonants were articulated more strongly than Wd-initial consonants. In Experiment 1, related targets were post-boundary words (e.g., tickets). No strengthening effect was observed (i.e., identity priming effects did not vary across splicing conditions). In Experiment 2, related targets were pre-boundary words (e.g., bus). There was a strengthening effect (stronger priming when the post-boundary CVs were spliced from IP-initial than from Wd-initial position), but only in Wd-boundary contexts. These were the conditions where phonetic detail associated with domain-initial strengthening could assist listeners most in lexical disambiguation. We discuss how speakers may strengthen domain-initial segments during production and how listeners may use the resulting acoustic correlates of prosodic strengthening during word recognition.

Abstract

Experiments 1 and 2 examined the time-course of retrieval of phonological, visual-shape and semantic knowledge as Dutch participants listened to sentences and looked at displays of four pictures. Given a sentence with beker, `beaker', for example, the display contained phonological (a beaver, bever), shape (a bobbin, klos), and semantic (a fork, vork) competitors. When the display appeared at sentence onset, fixations to phonological competitors preceded fixations to shape and semantic competitors. When display onset was 200 ms before (e.g.) beker, fixations were directed to shape and then semantic competitors, but not phonological competitors. In Experiments 3 and 4, displays contained the printed names of the previously-pictured entities; only phonological competitors were fixated preferentially. These findings suggest that retrieval of phonological, shape and semantic knowledge in the spoken-word and picture-recognition systems is cascaded, and that visual attention shifts are co-determined by the time-course of retrieval of all three knowledge types and by the nature of the information in the visual environment.

Abstract

Listeners use lexical knowledge to adjust their prelexical representations of speech sounds in response to the idiosyncratic pronunciations of particular speakers. We used an exposure-test paradigm to investigate whether this type of perceptual learning transfers across syllabic positions. No significant learning effect was found in Experiment 1, where exposure sounds were onsets and test sounds were codas. Experiments 2-4 showed that there was no learning even when both exposure and test sounds were onsets. But a trend was found when exposure sounds were codas and test sounds were onsets (Experiment 5). This trend was smaller than the robust effect previously found for the coda-to-coda case. These findings suggest that knowledge about idiosyncratic pronunciations may be position specific: Knowledge about how a speaker produces sounds in one position, if it can be acquired at all, influences perception of sounds in that position more strongly than of sounds in another position.

Abstract

Words repeated in the same voice are better recognized than when they are repeated in a different voice. Such findings have been taken as evidence for the storage of talker-specific lexical episodes. But results on perceptual learning suggest that talker-specific adjustments concern sublexical representations. This study thus investigates whether voice-specific repetition effects in auditory lexical decision are lexical or sublexical. The same critical set of items in Block 2 were, depending on materials in Block 1, either same-voice or different-voice word repetitions, new words comprising re-orderings of phonemes used in the same voice in Block 1, or new words with previously unused phonemes. Results show a benefit for words repeated by the same talker, and a smaller benefit for words consisting of phonemes repeated by the same talker. Talker-specific information thus appears to influence word recognition at multiple representational levels.

Abstract

Listeners use suprasegmental auditory lexical stress information to resolve the competition words engage in during spoken-word recognition. The present study investigated whether (a) visual speech provides lexical stress information, and, more importantly, (b) whether this visual lexical stress information is used to resolve lexical competition. Dutch word pairs that differ in the lexical stress realization of their first two syllables, but not segmentally (e.g., 'OCtopus' and 'okTOber'; capitals marking primary stress) served as auditory-only, visual-only, and audiovisual speech primes. These primes either matched (e.g., 'OCto-'), mismatched (e.g., 'okTO-'), or were unrelated to (e.g., 'maCHI-') a subsequent printed target (octopus), which participants had to make a lexical decision to. To the degree that visual speech contains lexical stress information, lexical decisions to printed targets should be modulated through the addition of visual speech. Results show, however, no evidence for a role of visual lexical stress information in audiovisual spoken-word recognition.

Abstract

Eye movements of Dutch participants were tracked as they looked at arrays of four words on a computer screen and followed spoken instructions (e.g., "Klik op het woord buffel": Click on the word buffalo). The arrays included the target (e.g., buffel), a phonological competitor (e.g., buffer, buffer), and two unrelated distractors. Targets were monosyllabic or bisyllabic, and competitors mismatched targets only on either their onset or offset phoneme and only by one distinctive feature. Participants looked at competitors more than at distractors, but this effect was much stronger for offset-mismatch than onset-mismatch competitors. Fixations to competitors started to decrease as soon as phonetic evidence disfavouring those competitors could influence behaviour. These results confirm that listeners continuously update their interpretation of words as the evidence in the speech signal unfolds and hence establish the viability of the methodology of using eye movements to arrays of printed words to track spoken-word recognition.

Abstract

This chapter is a review of the literature in experimental psycholinguistics on spoken word recognition. It is organized around eight questions. 1. Why are psycholinguists interested in spoken word recognition? 2. What information in the speech signal is used in word recognition? 3. Where are the words in the continuous speech stream? 4. Which words did the speaker intend? 5. When, as the speech signal unfolds over time, are the phonological forms of words recognized? 6. How are words recognized? 7. Whither spoken word recognition? 8. Who are the researchers in the field?

Abstract

We investigated perception of words with reduced word-final /t/ using an adapted eyetracking paradigm. Dutch listeners followed spoken instructions to click on printed words which were accompanied on a computer screen by simple shapes (e.g., a circle). Targets were either above or next to their shapes, and the shapes uniquely identified the targets when the spoken forms were ambiguous between words with or without final /t/ (e.g., bult, bump, vs. bul, diploma). Analysis of listeners’ eye-movements revealed, in contrast to earlier results, that listeners use the following segmental context when compensating for /t/-reduction. Reflecting that /t/-reduction is more likely to occur before bilabials, listeners were more likely to look at the /t/-final words if the next word’s first segment was bilabial. This result supports models of speech perception in which prelexical phonological processes use segmental context to modulate word recognition.

Abstract

Listeners can make perceptual adjustments to phoneme categories in response to a talker who consistently produces a specific phoneme ambiguously. We investigate here whether this type of perceptual learning is also used to adapt to regional accent differences. Listeners were exposed to words produced by a Flemish talker whose realization of [x℄or [h℄ was ambiguous (producing [x℄like [h℄is a property of the West-Flanders regional accent). Before and after exposure they categorized a [x℄-[h℄continuum. For both Dutch and Flemish listeners there was no shift of the categorization boundary after exposure to ambiguous sounds in [x℄- or [h℄-biasing contexts. The absence of a lexically-driven learning effect for this contrast may be because [h℄is strongly influenced by coarticulation. As is not stable across contexts, it may be futile to adapt its representation when new realizations are heard