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Janet F Werker

Publications and source records attributed to Janet F Werker.

14 recordsLinked to original sources
PubMed2006

Do you hear what I hear? Neural correlates of thought disorder during listening to speech in schizophrenia.

Thought disorder is a fundamental symptom of schizophrenia, observable as irregularities in speech. It has been associated with functional and structural abnormalities in brain regions involved in language processing, including left temporal regions, during language production tasks. We were interested in the neural correlates of thought disorder during receptive language processing, as this function is relatively preserved despite relying on the same brain regions as expressive language. Twelve patients with schizophrenia and 11 controls listened to 30-s speech samples while undergoing fMRI scanning. Thought disorder and global symptom ratings were obtained for each patient. Thought disorder but not global symptomatology correlated positively with the BOLD response in the left posterior superior temporal lobe while listening to comprehensible speech (cluster-level corrected p=.023). The pattern of brain activity associated with thought disorder during listening to comprehensible speech differs from that seen during language generation tasks, where a reduction of the leftward laterality of language has often been observed. As receptive language is spared in thought disorder, we propose that the increase in activation reflects compensatory processing allowing for normal performance.

Acoustic Stimulation↗
PubMed2006

Infant-directed speech supports phonetic category learning in English and Japanese.

Across the first year of life, infants show decreased sensitivity to phonetic differences not used in the native language [Werker, J. F., & Tees, R. C. (1984). Cross-language speech perception: evidence for perceptual reorganization during the first year of life. Infant Behaviour and Development, 7, 49-63]. In an artificial language learning manipulation, Maye, Werker, and Gerken [Maye, J., Werker, J. F., & Gerken, L. (2002). Infant sensitivity to distributional information can affect phonetic discrimination. Cognition, 82(3), B101-B111] found that infants change their speech sound categories as a function of the distributional properties of the input. For such a distributional learning mechanism to be functional, however, it is essential that the input speech contain distributional cues to support such perceptual learning. To test this, we recorded Japanese and English mothers teaching words to their infants. Acoustic analyses revealed language-specific differences in the distributions of the cues used by mothers (or cues present in the input) to distinguish the vowels. The robust availability of these cues in maternal speech adds support to the hypothesis that distributional learning is an important mechanism whereby infants establish native language phonetic categories.

Canada↗
PubMed2006

Cross-language sensitivity to phonotactic patterns in infants.

This study explored sensitivity to word-level phonotactic patterns in English and Japanese monolingual infants. Infants at the ages of 6, 12, and 18 months were tested on their ability to discriminate between test words using a habituation-switch experimental paradigm. All of the test words, neek, neeks, and neekusu, are phonotactically legitimate for English, whereas the first two words are critically noncanonical in Japanese. The language-specific phonotactical congruence influenced infants' performance in discrimination. English-learning infants could discriminate between neek and neeks at the age of 18 months, but Japanese infants could not. There was a similar developmental pattern for infants of both language groups for discrimination of neek and neeks, but Japanese infants showed a different trajectory from English infants for neekusu/neeks. These differences reflect the different status of these word patterns with respect to the phonotactics of both languages, and reveal early sensitivity to subtle phonotactic and language input patterns in each language.

Acoustic Stimulation↗
PubMed2005

Infant speech perception bootstraps word learning.

By their first birthday, infants can understand many spoken words. Research in cognitive development has long focused on the conceptual changes that accompany word learning, but learning new words also entails perceptual sophistication. Several developmental steps are required as infants learn to segment, identify and represent the phonetic forms of spoken words, and map those word forms to different concepts. We review recent research on how infants' perceptual systems unfold in the service of word learning, from initial sensitivity for speech to the learning of language-specific sound patterns. Building on a recent theoretical framework and emerging new methodologies, we show how speech perception is crucial for word learning, and suggest that it bootstraps the development of a separate but parallel phonological system that links sound to meaning.

Humans↗
PubMed2005

Speech perception as a window for understanding plasticity and commitment in language systems of the brain.

In this article, we provide a critical review of the literature on speech perception and phonological processing in infancy, and in populations with different experiential histories as a window to understanding how the notion of critical periods might apply to the acquisition of one part of language: the sound system. We begin by suggesting the use of the term "optimal period" because (a) both the onset (opening) and offset (closing) of openness to experience is variable rather than absolute and (b) phonological acquisition involves the emergence of a series of nested capabilities, each with its own sensitive period and each best explained at one of several different levels of specificity. In support, we cite evidence suggesting that to fully understand plasticity and commitment in phonological acquisition, it is necessary to consider not only the biological and experiential factors which may contribute to the onset and the offset of openness to experience but also how the sequentially developing parts of phonology constrain and direct development. In summary, we propose a nested, cascading model wherein biology, experience, and functional use each contribute.

Brain↗
PubMed2004

Is the integration of heard and seen speech mandatory for infants?

For adults and children, speech perception can be significantly influenced by watching a speaker's mouth movements. While recent reports suggest that infants may be able to integrate heard and seen speech, the current research demonstrates that integration is neither as strong or consistent in infants as it is in adults. Three habituation experiments were conducted. In Experiment 1, female (but not male) infants showed evidence of an adult pattern of integration following habituation with an audiovisual /bi/ and testing with audio /bi/-visual /vi/ (perceived as /vi/ by adults). The interpretation of integration was supported, but only in part, by Experiment 2. In Experiment 3, infants were habituated to a mismatched audio /bi/-visual /vi/ combination and tested on concordant /bi/-/bi/ versus /vi/-/vi/ displays. Here, only male infants showed evidence of integration. These results suggest that an initial mechanism supports integration, but that integration is not mandatory for young infants.

Adult↗
PubMed2004

Tuned to the signal: the privileged status of speech for young infants.

Do young infants treat speech as a special signal, compared with structurally similar non-speech sounds? We presented 2- to 7-month-old infants with nonsense speech sounds and complex non-speech analogues. The non-speech analogues retain many of the spectral and temporal properties of the speech signal, including the pitch contour information which is known to be salient to young listeners, and thus provide a stringent test for a potential listening bias for speech. Our results show that infants as young as 2 months of age listened longer to speech sounds. This listening selectivity indicates that early-functioning biases direct infants' attention to speech, granting speech a special status in relation to other sounds.

Attention↗
PubMed2004

Language experience and the organization of brain activity to phonetically similar words: ERP evidence from 14- and 20-month-olds.

The ability to discriminate phonetically similar speech sounds is evident quite early in development. However, inexperienced word learners do not always use this information in processing word meanings [Stager & Werker (1997). Nature, 388, 381-382]. The present study used event-related potentials (ERPs) to examine developmental changes from 14 to 20 months in brain activity important in processing phonetic detail in the context of meaningful words. ERPs were compared to three types of words: words whose meanings were known by the child (e.g., ''bear''), nonsense words that differed by an initial phoneme (e.g., ''gare''), and nonsense words that differed from the known words by more than one phoneme (e.g., ''kobe''). These results supported the behavioral findings suggesting that inexperienced word learners do not use information about phonetic detail when processing word meanings. For the 14-month-olds, ERPs to known words (e.g., ''bear'') differed from ERPs to phonetically dissimilar nonsense words (e.g., ''kobe''), but did not differ from ERPs to phonetically similar nonsense words (e.g., ''gare''), suggesting that known words and similar mispronunciations were processed as the same word. In contrast, for experienced word learners (i. e., 20-month-olds), ERPs to known words (e.g., ''bear'') differed from those to both types of nonsense words (''gare'' and ''kobe''). Changes in the lateral distribution of ERP differences to known and unknown (nonce) words between 14 and 20 months replicated previous findings. The findings suggested that vocabulary development is an important factor in the organization of neural systems linked to processing phonetic detail within the context of word comprehension.

Acoustic Stimulation↗
PubMed2003

Abnormal processing of speech during oddball target detection in schizophrenia.

Healthy subjects show increased activation in left temporal lobe regions in response to speech sounds compared to complex nonspeech sounds. Abnormal lateralization of speech-processing regions in the temporal lobes has been posited to be a cardinal feature of schizophrenia. Event-related fMRI was used to test the hypothesis that schizophrenic patients would show an abnormal pattern of hemispheric lateralization when detecting speech compared with complex nonspeech sounds in an auditory oddball target-detection task. We predicted that differential activation for speech in the vicinity of the superior temporal sulcus would be greater in schizophrenic patients than in healthy subjects in the right hemisphere, but less in patients than in healthy subjects in the left hemisphere. Fourteen patients with schizophrenia (selected from an outpatient population, 2 females, 12 males, mean age 35.1 years) and 29 healthy subjects (8 females, 21 males, mean age 29.3 years) were scanned while they performed an auditory oddball task in which the oddball stimuli were either speech sounds or complex nonspeech sounds. Compared to controls, individuals with schizophrenia showed greater differential activation between speech and nonspeech in right temporal cortex, left superior frontal cortex, and the left temporal-parietal junction. The magnitude of the difference in the left temporal parietal junction was significantly correlated with severity of disorganized thinking. This study supports the hypothesis that aberrant functional lateralization of speech processing is an underlying feature of schizophrenia and suggests the magnitude of the disturbance in speech-processing circuits may be associated with severity of disorganized thinking.

Adult↗
PubMed2003

Baby steps to learning language.

Young infants show remarkable speech perception sensitivities, and during the first year of life narrow these initial capabilities to reflect enhanced sensitivity to the sounds and structures used in their native language. This article reviews critical research illustrating how infants tune their perceptual sensitivities during the first year of life and how the language-specific changes in perception help "bootstrap" them into language. Specific discussion centers on recent research from our lab showing a link between the advances in speech perception and subsequent word learning in both normally developing and clinical populations, including research on the impact of early nutrition. The article ends with suggestions for new ways in which the milestones in speech and language processing seen in infancy can serve to help assess the role of early nutrition on subsequent development.

Age Factors↗
PubMed2003

Early word learners' ability to access phonetic detail in well-known words.

Several recent studies from our laboratory have shown that 14-month-old infants have difficulty learning to associate two phonetically similar new words to two different objects when tested in the Switch task. Because the infants can discriminate the same phonetic detail that they fail to use in the associative word-learning situation, we have argued that this word-learning failure results from a processing overload. Here we explore how infants perform in the Switch task with already known minimally different words. The experiment involved the same phonetic difference as used in our earlier word-learning studies. Following habituation to two familiar minimal pair object-label combinations (ball and doll), infants of 14 months looked longer to a violation in the object-label pairing (e.g., label 'ball' paired with object doll) than to an appropriate pairing. These results using well known words are consistent with the pattern of data recently obtained by Swingley and Aslin (2002) in which it was found that infants of 14 months look longer to the correct object when the accompanying well known word is spoken correctly rather than mispronounced. We discuss how these results are compatible with the limited resource explanation originally offered by Stager and Werker (1997).

Analysis of Variance↗
PubMed2002

Infants' ability to match dynamic phonetic and gender information in the face and voice.

Six experiments tested young infants' sensitivity to vowel and gender information in dynamic faces and voices. Infants were presented with side-by-side displays of two faces articulating the vowels /a/ or /i/ in synchrony. The heard voice matched the gender of one face in some studies and the vowel of one face in other studies and, in some studies, vowel and gender were placed in conflict. Infants of age 4.5 months showed no evidence of matching face and voice on the basis of gender, but were able to ignore irrelevant gender information and match on the basis of the vowel. Robust evidence of the ability to match on the basis of gender was not evident until 8 months of age. This set of findings suggests that, when identical stimuli are used, gender matching does not emerge until a later age than does phonetic matching. Results are discussed in relation to key theories of intermodal development.

Age Factors↗
PubMed2002

Infant sensitivity to distributional information can affect phonetic discrimination.

For nearly two decades it has been known that infants' perception of speech sounds is affected by native language input during the first year of life. However, definitive evidence of a mechanism to explain these developmental changes in speech perception has remained elusive. The present study provides the first evidence for such a mechanism, showing that the statistical distribution of phonetic variation in the speech signal influences whether 6- and 8-month-old infants discriminate a pair of speech sounds. We familiarized infants with speech sounds from a phonetic continuum, exhibiting either a bimodal or unimodal frequency distribution. During the test phase, only infants in the bimodal condition discriminated tokens from the endpoints of the continuum. These results demonstrate that infants are sensitive to the statistical distribution of speech sounds in the input language, and that this sensitivity influences speech perception.

Attention↗