Publications

Abstract

The automatic retuning of phoneme categories to better adapt to the speech of a novel talker has been extensively documented across various (neurotypical) populations, including both adults and children. However, no studies have examined auditory perceptual learning effects in populations atypical in perceptual, social, and language processing for communication, such as populations with autism. Employing a classic lexically-guided perceptual learning paradigm, the present study investigated perceptual learning effects in Australian English autistic and non-autistic adults. The findings revealed that automatic attunement to existing phoneme categories was not activated in the autistic group in the same manner as for non-autistic control subjects. Specifically, autistic adults were able to both successfully discern lexical items and to categorize speech sounds; however, they did not show effects of perceptual retuning to talkers. These findings may have implications for the application of current sensory theories (e.g., Bayesian decision theory) to speech and language processing by autistic individuals.
Lay Summary

Lexically guided perceptual learning assists in the disambiguation of speech from a novel talker. The present study established that while Australian English autistic adult listeners were able to successfully discern lexical items and categorize speech sounds in their native language, perceptual flexibility in updating speaker-specific phonemic knowledge when exposed to a novel talker was not available. Implications for speech and language processing by autistic individuals as well as current sensory theories are discussed.

Abstract

How do speakers of languages with different intonation systems produce and perceive prosodic junctures in sentences with identical structural ambiguity? Native speakers of English and of Mandarin produced potentially ambiguous sentences with a prosodic juncture either earlier in the utterance (e.g., “He gave her # dog biscuits,” “他给她#狗饼干 ”), or later (e.g., “He gave her dog # biscuits,” “他给她狗 #饼干 ”). These productiondata showed that prosodic disambiguation is realised very similarly in the two languages, despite some differences in the degree to which individual juncture cues (e.g., pausing) were favoured. In perception experiments with a new disambiguation task, requiring speeded responses to select the correct meaning for structurally ambiguous sentences, language differences in disambiguation response time appeared: Mandarin speakers correctly disambiguated sentences with earlier juncture faster than those with later juncture, while English speakers showed the reverse. Mandarin-speakers with L2 English did not show their native-language response time pattern when they heard the English ambiguous sentences. Thus even with identical structural ambiguity and identically cued production, prosodic juncture perception across languages can differ.

Abstract

As many distributional learning (DL) studies have shown, adult listeners can achieve discrimination of a difficult non-native contrast after a short repetitive exposure to tokens falling at the extremes of that contrast. Such studies have shown using behavioural methods that a short distributional training can induce perceptual learning of vowel and consonant contrasts. However, much less is known about the neurological correlates of DL, and few studies have examined non-native lexical tone contrasts. Here, Australian-English speakers underwent DL training on a Mandarin tone contrast using behavioural (discrimination, identification) and neural (oddball-EEG) tasks, with listeners hearing either a bimodal or a unimodal distribution. Behavioural results show that listeners learned to discriminate tones after both unimodal and bimodal training; while EEG responses revealed more learning for listeners exposed to the bimodal distribution. Thus, perceptual learning through exposure to brief sound distributions (a) extends to non-native tonal contrasts, and (b) is sensitive to task, phonetic distance, and acoustic cue-weighting. Our findings have implications for models of how auditory and phonetic constraints influence speech learning.

Abstract

Children adopted early in life into another linguistic community typically forget their birth language but retain, unaware, relevant linguistic knowledge that may facilitate (re)learning of birth-language patterns. Understanding the nature of this knowledge can shed light on how language is acquired. Here, international adoptees from Korea with Dutch as their current language, and matched Dutch-native controls, provided speech production data on a Korean consonantal distinction unlike any Dutch distinctions, at the outset and end of an intensive perceptual training. The productions, elicited in a repetition task, were identified and rated by Korean listeners. Adoptees' production scores improved significantly more across the training period than control participants' scores, and, for adoptees only, relative production success correlated significantly with the rate of learning in perception (which had, as predicted, also surpassed that of the controls). Of the adoptee group, half had been adopted at 17 months or older (when talking would have begun), while half had been prelinguistic (under six months). The former group, with production experience, showed no advantage over the group without. Thus the adoptees' retained knowledge of Korean transferred from perception to production and appears to be abstract in nature rather than dependent on the amount of experience.

Abstract

Until at least 6 mo of age, infants show good discrimination for familiar phonetic contrasts (i.e., those heard in the environmental language) and contrasts that are unfamiliar. Adult-like discrimination (significantly worse for nonnative than for native contrasts) appears only later, by 9–10 mo. This has been interpreted as indicating that infants have no knowledge of phonology until vocabulary development begins, after 6 mo of age. Recently, however, word recognition has been observed before age 6 mo, apparently decoupling the vocabulary and phonology acquisition processes. Here we show that phonological acquisition is also in progress before 6 mo of age. The evidence comes from retention of birth-language knowledge in international adoptees. In the largest ever such study, we recruited 29 adult Dutch speakers who had been adopted from Korea when young and had no conscious knowledge of Korean language at all. Half were adopted at age 3–5 mo (before native-specific discrimination develops) and half at 17 mo or older (after word learning has begun). In a short intensive training program, we observe that adoptees (compared with 29 matched controls) more rapidly learn tripartite Korean consonant distinctions without counterparts in their later-acquired Dutch, suggesting that the adoptees retained phonological knowledge about the Korean distinction. The advantage is equivalent for the younger-adopted and the older-adopted groups, and both groups not only acquire the tripartite distinction for the trained consonants but also generalize it to untrained consonants. Although infants younger than 6 mo can still discriminate unfamiliar phonetic distinctions, this finding indicates that native-language phonological knowledge is nonetheless being acquired at that age.

Abstract

Background/Aims: Evidence from spoken word recognition suggests that for English listeners, distinguishing full versus reduced vowels is important, but discerning stress differences involving the same full vowel (as in mu- from music or museum) is not. In Dutch, in contrast, the latter distinction is important. This difference arises from the relative frequency of unstressed full vowels in the two vocabularies. The goal of this paper is to determine how this difference in the lexicon influences the perception of stressed versus unstressed vowels. Methods: All possible sequences of two segments (diphones) in Dutch and in English were presented to native listeners in gated fragments. We recorded identification performance over time throughout the speech signal. The data were here analysed specifically for patterns in perception of stressed versus unstressed vowels. Results: The data reveal significantly larger stress effects (whereby unstressed vowels are harder to identify than stressed vowels) in English than in Dutch. Both language-specific and shared patterns appear regarding which vowels show stress effects. Conclusion: We explain the larger stress effect in English as reflecting the processing demands caused by the difference in use of unstressed vowels in the lexicon. The larger stress effect in English is due to relative inexperience with processing unstressed full vowels

Abstract

Orthographies encode phonological information only at the level of words (chiefly, the information encoded concerns phonetic segments; in some cases, tonal information or default stress may be encoded). Of primary interest to second language (L2) learners is whether orthography can assist in clarifying L2 phonological distinctions that are particularly difficult to perceive (e.g., where one native-language phonemic category captures two L2 categories). A review of spoken-word recognition evidence suggests that orthographic information can install knowledge of such a distinction in lexical representations but that this does not affect learners’ ability to perceive the phonemic distinction in speech. Words containing the difficult phonemes become even harder for L2 listeners to recognize, because perception maps less accurately to lexical content.

Abstract

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

Abstract

In four experiments, listeners’ response times to detect vowel targets in spoken input were measured. The first three experiments were conducted in English. In two, one using real words and the other, nonwords, detection accuracy was low, targets in initial syllables were detected more slowly than targets in final syllables, and both response time and missed-response rate were inversely correlated with vowel duration. In a third experiment, the speech context for some subjects included all English vowels, while for others, only five relatively distinct vowels occurred. This manipulation had essentially no effect, and the same response pattern was again observed. A fourth experiment, conducted in Spanish, replicated the results in the first three experiments, except that miss rate was here unrelated to vowel duration. We propose that listeners’ responses to vowel targets in naturally spoken input are effectively cautious, reflecting realistic appreciation of vowel variability in natural context.

Abstract

Nasal consonants in syllabic coda position in Japanese assimilate to the place of articulation of a following consonant. The resulting forms may be perceived as different realizations of a single underlying unit, and indeed the kana orthographies represent them with a single character. In the present study, Japanese listeners' response time to detect nasal consonants was measured. Nasals in coda position, i.e., moraic nasals, were detected faster and more accurately than nonmoraic nasals, as reported in previous studies. The place of articulation with which moraic nasals were realized affected neither response time nor accuracy. Non-native subjects who knew no Japanese, given the same materials with the same instructions, simply failed to respond to moraic nasals which were realized bilabially. When the nasals were cross-spliced across place of articulation contexts the Japanese listeners still showed no significant place of articulation effects, although responses were faster and more accurate to unspliced than to cross-spliced nasals. When asked to detect the phoneme following the (cross-spliced) moraic nasal, Japanese listeners showed effects of mismatch between nasal and context, but non-native listeners did not. Together, these results suggest that Japanese listeners are capable of very rapid abstraction from phonetic realization to a unitary representation of moraic nasals; but they can also use the phonetic realization of a moraic nasal effectively to obtain anticipatory information about following phonemes.

Abstract

In languages with variable stress placement, lexical stress patterns can convey information about word identity. The experiments reported here address the question of whether lexical stress information can be used in word recognition. The results allow the following conclusions: 1. Prior information as to the number of syllables and lexical stress patterns of words and nonwords does not facilitate lexical decision responses (Experiment 1). 2. The strong correspondences between grammatical category membership and stress pattern in bisyllabic English words (strong-weak stress being associated primarily with nouns, weak-strong with verbs) are not exploited in the recognition of isolated words (Experiment 2). 3. When a change in lexical stress also involves a change in vowel quality, i.e., a segmental as well as a suprasegmental alteration, effects on word recognition are greater when no segmental correlates of suprasegmental changes are involved (Experiments 2 and 3). 4. Despite the above finding, when all other factors are controlled, lexical stress information per se can indeed be shown to play a part in word-recognition process (Experiment 3).

Abstract

Recent research in speech production has shown that syntactic structure is reflected in segmental phonology--the application of certain phonological rules of English (e.g., palatalization and alveolar flapping) is inhibited across phrase boundaries. We examined whether such segmental effects can be used in speech perception as cues to syntactic structure, and the relation between the use of these segmental features as syntactic markers in production and perception. Speakers of American English (a dialect in which the above segmental effects occur) could indeed use the segmental cues in syntax perception; speakers of British English (in which the effects do not occur) were unable to make use of them, while speakers of British English who were long-term residents of the United States showed intermediate performance.

Abstract

Infants acquire whatever language is spoken in the environment into which they are born. The mental capability of the newborn child is not biased in any way towards the acquisition of one human language rather than another. Because psychologists who attempt to model the process of language comprehension are interested in the structure of the human mind, rather than in the properties of individual languages, strategies which they incorporate in their models are presumed to be universal, not language-specific. In other words, strategies of comprehension are presumed to be characteristic of the human language processing system, rather than, say, the French, English, or Igbo language processing systems. We report here, however, on a comprehension strategy which appears to be used by native speakers of French but not by native speakers of English.

Abstract

Spontaneous self-corrections in speech pose a communication problem; the speaker must make clear to the listener not only that the original Utterance was faulty, but where it was faulty and how the fault is to be corrected. Prosodic marking of corrections - making the prosody of the repair noticeably different from that of the original utterance - offers a resource which the speaker can exploit to provide the listener with such information. A corpus of more than 400 spontaneous speech repairs was analysed, and the prosodic characteristics compared with the syntactic and semantic characteristics of each repair. Prosodic marking showed no relationship at all with the syntactic characteristics of repairs. Instead, marking was associated with certain semantic factors: repairs were marked when the original utterance had been actually erroneous, rather than simply less appropriate than the repair; and repairs tended to be marked more often when the set of items encompassing the error and the repair was small rather than when it was large. These findings lend further weight to the characterization of accent as essentially semantic in function.

Abstract

In an earlier study, it was shown that listeners can use prosodic cues that predict where sentence stress will fall; phoneme-monitoring RTs are faster when the preceding prosody indicates that the word bearing the target will be stressed. Two experiments which further investigate this effect are described. In the first, it is shown that the duration of the closure preceding the release of the target stop consonant burst does not affect the RT advantage for stressed words. In the second, it is shown that fundamental frequency variation is not a necessary component of the prosodic variation that produces the predicted-stress effect. It is argued that sentence processing involves a very flexible use of prosodic information.

Abstract

Reaction time to detect a phoneme target in a sentence was found to be faster when the word in which the target occurred formed part of the semantic focus of the sentence. Focus was determined by asking a question before the sentence; that part of the sentence which comprised the answer to the sentence was assumed to be focussed. This procedure made it possible to vary position offocus within the sentence while holding all acoustic aspects of the sentence itself constant. It is argued that sentence understanding is facilitated by rapid identification of focussed information. Since focussed words are usually accented, it is further argued that the active search for accented words demonstrated in previous research should be interpreted as a search for semantic focus.