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PubMed2006

Stimulus variability and the phonetic relevance hypothesis: effects of variability in speaking style, fundamental frequency, and speaking rate on spoken word identification.

Three experiments were conducted to examine the effects of trial-to-trial variations in speaking style, fundamental frequency, and speaking rate on identification of spoken words. In addition, the experiments investigated whether any effects of stimulus variability would be modulated by phonetic confusability (i.e., lexical difficulty). In Experiment 1, trial-to-trial variations in speaking style reduced the overall identification performance compared with conditions containing no speaking-style variability. In addition, the effects of variability were greater for phonetically confusable words than for phonetically distinct words. In Experiment 2, variations in fundamental frequency were found to have no significant effects on spoken word identification and did not interact with lexical difficulty. In Experiment 3, two different methods for varying speaking rate were found to have equivalent negative effects on spoken word recognition and similar interactions with lexical difficulty. Overall, the findings are consistent with a phonetic-relevance hypothesis, in which accommodating sources of acoustic-phonetic variability that affect phonetically relevant properties of speech signals can impair spoken word identification. In contrast, variability in parameters of the speech signal that do not affect phonetically relevant properties are not expected to affect overall identification performance. Implications of these findings for the nature and development of lexical representations are discussed.

Adolescent↗
PubMed1990

Phonetic variation in multisyllable babbling.

This investigation examined phonetic variation in multisyllable babbling of infants from 0.7 to 0.11. The basis of this investigation was to examine assumptions present in major models of infant vocal development which suggest systematic developmental increases in phonetic variation of these babbles, and posit separate stages of repetitive (multisyllables with non-varied phonetic elements) and non-repetitive (phonetically varied multisyllables) babbling. Eight infants were audiotaperecorded in their homes at ages 0.7, 0.9 and 0.11. The multisyllable vocalizations were categorized based on the presence or absence of phonetic variation, and the source of that variation (place change, manner change or both). Multisyllables were produced with phonetic variation at or near the beginning of multisyllable babbling, which failed to support the existence of distinct stages of repetitive and nonrepetitive babbling.

Humans↗
PubMed1997

Infants listen for more phonetic detail in speech perception than in word-learning tasks.

Infants aged 4-6 months discriminate the fine phonetic differences that distinguish syllables in both their native and unfamiliar languages, but by 10-12 months their perceptual sensitivities are reorganized so that they discriminate only the phonetic variations that are used to distinguish meaning in their native language. It would seem, then, that infants apply their well honed phonetic sensitivities as they advance and begin to associate words with objects, but the question of how speech perception sensitivities are used in early word learning has not yet been answered. Here we use a recently developed technique to show that when they are required to pair words with objects, infants of 14 months fail to use the fine phonetic detail they detect in syllable discrimination tasks. In contrast, infants of 8 months--who are not yet readily learning words--successfully discriminate phonetic detail in the same task in which infants aged 14 months fail. Taken together, these results suggest a second reorganization in infants's use of phonetic detail as they move from listening to syllables to learning words.

Aging↗
PubMed2006

Infants show a facilitation effect for native language phonetic perception between 6 and 12 months.

Patterns of developmental change in phonetic perception are critical to theory development. Many previous studies document a decline in nonnative phonetic perception between 6 and 12 months of age. However, much less experimental attention has been paid to developmental change in native-language phonetic perception over the same time period. We hypothesized that language experience in the first year facilitates native-language phonetic performance between 6 and 12 months of age. We tested 6-8- and 10-12-month-old infants in the United States and Japan to examine native and nonnative patterns of developmental change using the American English /r-l/ contrast. The goals of the experiment were to: (a) determine whether facilitation characterizes native-language phonetic change between 6 and 12 months of age, (b) examine the decline previously observed for nonnative contrasts and (c) test directional asymmetries for consonants. The results show a significant increase in performance for the native-language contrast in the first year, a decline in nonnative perception over the same time period, and indicate directional asymmetries that are constant across age and culture. We argue that neural commitment to native-language phonetic properties explains the pattern of developmental change in the first year.

Age Factors↗
PubMed1991

The role of phonetics within the study of language.

Phonologists have often held that phonetic 'substance' is more or less unrelated to phonological 'form'. This view rests on assumptions about the phonetic domain that are highly questionable on empirical grounds. Evidence is reviewed suggesting that very few phonetic properties of vowels fail to serve the linguistic function of preserving and enhancing distinctiveness. Accordingly, much of what has been considered to be purely phonetic is also phonological in character: that is to say, the domains of phonetics and phonology overlap significantly. Finally, several well-known criticisms of the program of phonetic explanation in phonology are discussed and rejected.

Humans↗
PubMed2003

Short-term reorganization of auditory analysis induced by phonetic experience.

Sine wave replicas of spoken words can be perceived both as nonphonetic auditory forms and as words, depending on a listener's experience. In this study, brain areas activated by sine wave words were studied with fMRI in two conditions: when subjects perceived the sounds spontaneously as nonphonetic auditory forms ("nïve condition") and after instruction and brief practice attending to their phonetic attributes ("informed condition"). The test items were composed such that half replicated natural words ("phonetic items") and the other half did not, because the tone analogs of the first and third formants had been temporally reversed ("nonphonetic items"). Subjects were asked to decide whether an isolated tone analog of the second formant (T2) presented before the sine wave word (T1234) was included in it. Experience in attending to the phonetic properties of the sinusoids interfered with this auditory matching task and was accompanied by a decrease in auditory cortex activation with word replicas but not with the acoustically matched nonphonetic items. Because the activation patterns elicited by equivalent acoustic test items depended on a listener's awareness of their phonetic potential, this indicates that the analysis of speech sounds in the auditory cortex is distinct from the simple resolution of auditory form, and is not a mere consequence of acoustic complexity. Because arbitrary acoustic patterns did not evoke the response observed for phonetic patterns, these findings suggest that the perception of speech is contingent on the presence of familiar patterns of spectral variation. The results are consistent with a short-term functional reorganization of auditory analysis induced by phonetic experience with sine wave replicas and contingent on the dynamic acoustic structure of speech.

Adolescent↗
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↗
PubMed1977

Visual and phonetic memory in preschool children: evidence for coding flexibility.

This study examined visual and verbal (phonetic) memory coding in 22 preschool children 4 to 5 yr. of age. A major goal was to determine whether these children would code visual items phonetically during input in a short-term memory task as older children and adults often appear to do. Items to be remembered were visually presented letters that varied in visual as well as phonetic similarity. Subjects labeled each letter during presentation, and serial recall was probed either visually or verbally. Recall scores were analyzed according to planned individual comparisons and a 4-factor analysis of variance: probe modality (visual, verbal) X visual similarity (low, high) X phonetic similarity (low, high) x serial position (1, 2, 3, 4). Data indicated (1) a significant detrimental effect of high phonetic similarity for subjects whose recall was probed verbally, (2) a significant facilitating effect of high visual similarity, and (3) significant interactions indicating differential effects of phonetic similarity and probe modality on the serial position curve. These findings suggest flexibility of coding in children of the age range tested.

Adult↗
PubMed1984

Development of phonetic memory in disabled and normal readers.

The development of phonetic codes in memory of 141 pairs of normal and disabled readers from 7.8 to 16.8 years of age was tested with a task adapted from L. S. Mark, D. Shankweiler, I. Y. Liberman, and C. A. Fowler (Memory & Cognition, 1977, 5, 623-629) that measured false-positive errors in recognition memory for foil words which rhymed with words in the memory list versus foil words that did not rhyme. Our younger subjects replicated Mark et al., showing a larger difference between rhyming and nonrhyming false-positive errors for the normal readers. The older disabled readers' phonetic effect was comparable to that of the younger normal readers, suggesting a developmental lag in their use of phonetic coding in memory. Surprisingly, the normal readers' phonetic effect declined with age in the recognition task, but they maintained a significant advantage across age in the auditory WISC-R digit span recall test, and a test of phonological nonword decoding. The normals' decline with age in rhyming confusion may be due to an increase in the precision of their phonetic codes.

Adolescent↗
PubMed2004

Predicting stuttering from phonetic complexity in German.

UNLABELLED: This study investigated how phonetic complexity affects stuttering rate in German and how this changes developmentally. Phonetic difficulty was assessed using Jakielski's index [Motor Organization in the Acquisition of Consonant Clusters, Dissertation/Ph.D. Thesis, University of Texas Austin, 1998] of phonetic complexity (IPC) in which words are scored on eight different characteristics. Stuttering rate was not related to IPC score for German function words, as previously shown for Spanish and English. Significant correlations between stuttering rate and IPC score were found for content words for children over the age of six and adults. It was also found that German content words have a higher mean IPC sum compared to their English counterparts. There was a bigger difference in IPC score between fluent and stuttered words in German than in English. Factor 5 (word shape) influenced stuttering rates in both German age groups. This has also been found for Spanish but does not apply to English. EDUCATIONAL OBJECTIVES: The reader will be able to: (1) describe a method to measure phonetic complexity and how this affects stuttering rates for words of different grammatical classes; (2) explain why this method is suitable for different languages and age groups; (3) detect which phonetic characteristics have most impact on different age groups in English and German; (4) assess possible theoretical reasons for these findings.

Adolescent↗
PubMed2006

Phonetic processing areas revealed by sinewave speech and acoustically similar non-speech.

The neural substrates underlying speech perception are still not well understood. Previously, we found dissociation of speech and nonspeech processing at the earliest cortical level (AI), using speech and nonspeech complexity dimensions. Acoustic differences between speech and nonspeech stimuli in imaging studies, however, confound the search for linguistic-phonetic regions. Presently, we used sinewave speech (SWsp) and nonspeech (SWnon), which replace speech formants with sinewave tones, in order to match acoustic spectral and temporal complexity while contrasting phonetics. Chord progressions (CP) were used to remove the effects of auditory coherence and object processing. Twelve normal RH volunteers were scanned with fMRI while listening to SWsp, SWnon, CP, and a baseline condition arranged in blocks. Only two brain regions, in bilateral superior temporal sulcus, extending more posteriorly on the left, were found to prefer the SWsp condition after accounting for acoustic modulation and coherence effects. Two regions responded preferentially to the more frequency-modulated stimuli, including one that overlapped the right temporal phonetic area and another in the left angular gyrus far from the phonetic area. These findings are proposed to form the basis for the two subtypes of auditory word deafness. Several brain regions, including auditory and non-auditory areas, preferred the coherent auditory stimuli and are likely involved in auditory object recognition. The design of the current study allowed for separation of acoustic spectrotemporal, object recognition, and phonetic effects resulting in distinct and overlapping components.

Adolescent↗
PubMed1984

Effect of lexical status on phonetic categorization.

To investigate the interaction in speech perception between lexical knowledge (in particular, whether a stimulus token makes a word or nonword) and phonetic categorization, sets of [bVC]-[dVC] place-of-articulation continua were constructed so that the endpoint tokens represented word-word, word-nonword, nonword-word, and nonword-nonword combinations. Experiment 1 demonstrated that ambiguous tokens were perceived in favor of the word token and supported the contention that lexical knowledge can affect the process of phonetic categorization. Experiment 2 utilized a reaction time procedure with the same stimuli and demonstrated that the effect of lexical status on phonetic categorization increased with response latency, suggesting that the lexical effect represents a perceptual process that is separate from and follows phonetic categorization. Experiment 3 utilized a different set of [b-d] continua to separate the effects of final consonant contrast and lexical status that were confounded in Experiments 1 and 2. Results demonstrated that both lexical status and contextual contrast separately affected the identification of the initial stop. Data from these three experiments support a perceptual model wherein phonetic categorization can operate separately from higher levels of analysis.

Humans↗
PubMed1993

Phonetic coherence in duplex perception: effects of acoustic differences and lexical status.

A modified version of duplex perception was used to investigate the nature of perceptual organization of speech. Ss were asked to identify stimuli in which a third-formant transition was presented to 1 ear and a full syllable (base) was presented to the other ear. Phonetic integration occurred even when the spectral composition or onset frequency of the isolated transition was varied relative to the base. However, when onset asynchronies were added to spectral differences, the isolated transition ceased to contribute to the syllable percept. Lexical status of the eventual phonetic percepts also influenced the phonetic integration of acoustic components into syllable percepts. These results suggest that combinations of low-level acoustic and phonetic differences between components and higher level lexical information interact to influence the grouping of acoustic components into phonetic percepts.

Adult↗
PubMed2003

Foreign-language experience in infancy: effects of short-term exposure and social interaction on phonetic learning.

Infants acquire language with remarkable speed, although little is known about the mechanisms that underlie the acquisition process. Studies of the phonetic units of language have shown that early in life, infants are capable of discerning differences among the phonetic units of all languages, including native- and foreign-language sounds. Between 6 and 12 mo of age, the ability to discriminate foreign-language phonetic units sharply declines. In two studies, we investigate the necessary and sufficient conditions for reversing this decline in foreign-language phonetic perception. In Experiment 1, 9-mo-old American infants were exposed to native Mandarin Chinese speakers in 12 laboratory sessions. A control group also participated in 12 language sessions but heard only English. Subsequent tests of Mandarin speech perception demonstrated that exposure to Mandarin reversed the decline seen in the English control group. In Experiment 2, infants were exposed to the same foreign-language speakers and materials via audiovisual or audio-only recordings. The results demonstrated that exposure to recorded Mandarin, without interpersonal interaction, had no effect. Between 9 and 10 mo of age, infants show phonetic learning from live, but not prerecorded, exposure to a foreign language, suggesting a learning process that does not require long-term listening and is enhanced by social interaction.

Female↗
PubMed1983

Phonetic coding in marginally competent readers.

Findings from recent studies suggest that children with reading disorders are deficient in coding the phonetic features of letters in memory, and that this deficiency is apparent whether the letters are presented visually or auditorily. The present investigation represents an additional test of the phonetic-deficit hypothesis. Ss in this experiment were 16 children classified as marginally competent readers and 16 children classified as good readers. Their task was to recall rhyming or nonrhyming letter sequences presented either visually or auditorily. Marginal readers showed less evidence of phonetic coding than good readers, whether letter presentations were visual or auditory, as in previous studies. However, analyses carried out separately on the data of each reading group suggest that marginal readers were capable of phonetic coding, at least when letter presentations were auditory. These findings raise the possibility that the phonetic-coding deficiency shown by children who are subaverage readers is not as pervasive as has been suggested previously.

Child↗
PubMed1983

A possible auditory basis for internal structure of phonetic categories.

We used a selective adaptation procedure to investigate the possibility that differences in the degree to which stimuli within a phonetic category are considered to be good exemplars of the category--that is, differences in perceived category goodness--have a basis at a prephonetic, auditory level of processing. For three different phonetic contrasts (/b-p/, /d-g/, /b-w/), we assessed the relative magnitude of adaptation along a stimulus continuum produced by a variety of stimuli from the continuum belonging to a given phonetic category. For all three phonetic contrasts, nonmonotonic adaptation functions were obtained: As the adaptor moved away from the category boundary, there was an initial increase in adaptation, followed by a subsequent decrease. On the assumption that selective adaptation taps a prephonetic, auditory level of processing, these findings permit the following conclusions. First, at an auditory level there is a limit on the range of stimuli along a continuum that is treated as relevant to a given contrast; that is, the stimuli along a continuum are effectively grouped into auditory categories. Second, stimuli within an auditory category vary in their effectiveness as category members, providing an internal structure to the categories. Finally, this internal category structure at the auditory level, revealed by the adaptation procedure, may provide a basis for differences in perceived category goodness at the phonetic level.

Adaptation, Physiological↗
PubMed1984

Phonemic and phonetic factors in adult cross-language speech perception.

Previous research has indicated that young infants can discriminate speech sounds across phonetic boundaries regardless of specific relevant experience, and that there is a modification in this ability during ontogeny such that adults often have difficulty discriminating phonetic contrasts which are not used contrastively in their native language. This pattern of findings has often been interpreted as suggesting that humans are endowed with innate auditory sensitivities which enable them to discriminate speech sounds according to universal phonetic boundaries and that there is a decline or loss in this ability after being exposed to a language which contrasts only a subset of those distinctions. The present experiments were designed to determine whether this modification represents a loss of sensorineural response capabilities or whether it shows a shift in attentional focus and/or processing strategies. In experiment 1, adult English-speaking subjects were tested on their ability to discriminate two non-English speech contrasts in a category-change discrimination task after first being predisposed to adopt one of four perceptual sets. In experiments 2, 3, and 4 subjects were tested in an AX (same/different) procedure, and the effects of both limited training and duration of the interstimulus interval were assessed. Results suggest that the previously observed ontogenetic modification in the perception of non-native phonetic contrasts involves a change in processing strategies rather than a sensorineural loss. Adult listeners can discriminate sounds across non-native phonetic categories in some testing conditions, but are not able to use that ability in testing conditions which have demands similar to those required in natural language processing.

Adolescent↗
PubMed2001

Contextual influences on the internal structure of phonetic categories: a distinction between lexical status and speaking rate.

Previous research has shown that phonetic categories have a graded internal structure that is highly dependent on acoustic-phonetic contextual factors, such as speaking rate; these factors alter not only the location of phonetic category boundaries, but also the location of a category's best exemplars. The purpose of the present investigation, which focused on the voiceless category as specified by voice onset time (VOT), was to determine whether a higher order linguistic contextual factor, lexical status, which is known to alter the location of the voiced-voiceless phonetic category boundary, also alters the location of the best exemplars of the voiceless category. The results indicated that lexical status has a more limited and qualitatively different effect on the category's best exemplars than does the acoustic-phonetic factor of speaking rate. This dissociation is discussed in terms of a production-based account in which perceived best exemplars of a category track contextual variation in speech production.

Adolescent↗