Jessica F. Hay

Learning in reverse: Eight-month-old infants track backward transitional probabilities

Numerous recent studies suggest that human learners, including both infants and adults, readily track sequential statistics computed between adjacent elements. One such statistic, transitional probability, is typically calculated as the likelihood that one element predicts another. However, little is known about whether listeners are sensitive to the directionality of this computation. To address this issue, we tested 8-month-old infants in a word segmentation task, using fluent speech drawn from an unfamiliar natural language. Critically, test items were distinguished solely by their backward transitional probabilities. The results provide the first evidence that infants track backward statistics in fluent speech.

Perception of rhythmic grouping : Testing the iambic/trochaic law

This study was designed to test the iambic/trochaic law, which claims that elements contrasting in duration naturally form rhythmic groupings with final prominence, whereas elements contrasting in intensity form groupings with initial prominence. It was also designed to evaluate whether the iambic/trochaic law describes general auditory biases, or whether rhythmic grouping is speech or language specific. In two experiments, listeners were presented with sequences of alternating /ga/ syllables or square wave segments that varied in either duration or intensity and were asked to indicate whether they heard a trochaic (i.e., strong-weak) or an iambic (i.e., weak-strong) rhythmic pattern. Experiment 1 provided a validation of the iambic/trochaic law in Englishs-peaking listeners; for both speech and nonspeech stimuli, variations in duration resulted in iambic grouping, whereas variations in intensity resulted in trochaic grouping. In Experiment 2, no significant differences were found between the rhythmic-grouping performances of English- and French-speaking listeners. The speech/nonspeech and cross-language parallels suggest that the perception of linguistic rhythm relies largely on general auditory mechanisms. The applicability of the iambic/trochaic law to speech segmentation is discussed.

Enhanced contrast for vowels in utterance focus : A cross-language study

The present study examined several potential distinctiveness-enhancing correlates of vowels produced in utterance focus by talkers of American English, French, and German. These correlates included possible increases in vowel space size, in formant movement within individual vowels, and in duration variance among vowels. Each language group enhanced the distinctiveness of vowels in [+focus] context but used somewhat differing means to achieve this. All three groups used spectral differences, but only German talkers used durational differences, to enhance distinctiveness. The results suggest that the amount of distinctiveness enhancement of a vowel property in [+focus] context is positively related to the between-category variation of that property in [-focus] context. Thus, consistent with the theory of adaptive dispersion, utterance clarity appears to vary directly with information content.

How auditory discontinuities and linguistic experience affect the perception of speech and non‐speech in English‐ and Spanish‐speaking listeners

The present study was designed to investigate the effects of long‐term linguistic experience on the perception of non‐speech sounds in English and Spanish speakers. Research using tone‐onset‐time (TOT) stimuli, a type of non‐speech analogue of voice‐onset‐time (VOT) stimuli, has suggested that there is an underlying auditory basis for the perception of stop consonants based on a threshold for detecting onset asynchronies in the vicinity of +20 ms. For English listeners, stop consonant labeling boundaries are congruent with the positive auditory discontinuity, while Spanish speakers place their VOT labeling boundaries and discrimination peaks in the vicinity of 0 ms VOT. The present study addresses the question of whether long‐term linguistic experience with different VOT categories affects the perception of non‐speech stimuli that are analogous in their acoustic timing characteristics. A series of synthetic VOT stimuli and TOT stimuli were created for this study. Using language appropriate labeling and ABX discrimination tasks, labeling boundaries (VOT) and discrimination peaks (VOT and TOT) are assessed for 24 monolingual English speakers and 24 monolingual Spanish speakers. The interplay between language experience and auditory biases are discussed. [Work supported by NIDCD.]

Multimodal imaging of temporal processing in typical and atypical language development

New approaches to understanding language and reading acquisition propose that the human brains ability to synchronize its neural firing rate to syllable‐length linguistic units may be important to childrens ability to acquire human language. Yet, little evidence from brain imaging studies has been available to support this proposal. Here, we summarize three recent brain imaging (functional near‐infrared spectroscopy (fNIRS), functional magnetic resonance imaging (fMRI), and magnetoencephalography (MEG)) studies from our laboratories with young English‐speaking children (aged 6–12 years). In the first study (fNIRS), we used an auditory beat perception task to show that, in children, the left superior temporal gyrus (STG) responds preferentially to rhythmic beats at 1.5 Hz. In the second study (fMRI), we found correlations between childrens amplitude rise–time sensitivity, phonological awareness, and brain activation in the left STG. In the third study (MEG), typically developing children outperformed children with autism spectrum disorder in extracting words from rhythmically rich foreign speech and displayed different brain activation during the learning phase. The overall findings suggest that the efficiency with which left temporal regions process slow temporal (rhythmic) information may be important for gains in language and reading proficiency. These findings carry implications for better understanding of the brains mechanisms that support language and reading acquisition during both typical and atypical development.

A cross‐language study of vowel sounds produced with and without emphasis: Testing the theory of adaptive dispersion

According to Lindbloms Theory of Adaptive Dispersion (TAD), the aim of talkers is to make phonological contrasts sufficiently distinctive to promote linguistic comprehension by the listener while minimizing the articulatory effort needed to achieve this degree of distinctiveness. When part of an utterance carries new—rather than given—information, it tends to be spoken with greater emphasis and clarity. In this study, several possible acoustic correlates of vowels in emphasized words were examined in American English, French, and Japanese in comparable phonetic and sentence contexts. These possible correlates include an expanded vowel space, greater vowel inherent spectral change, and a greater systematic variation in vowel length. Preliminary analyses suggest that the contrast‐enhancing properties of emphasized vowels vary considerably across languages. [Work supported by NIDCD.]

The Longevity of Statistical Learning: When Infant Memory Decays, Isolated Words Come to the Rescue.

Research over the past 2 decades has demonstrated that infants are equipped with remarkable computational abilities that allow them to find words in continuous speech. Infants can encode information about the transitional probability (TP) between syllables to segment words from artificial and natural languages. As previous research has tested infants immediately after familiarization, infants’ ability to retain sequential statistics beyond the immediate familiarization context remains unknown. Here, we examine infants’ memory for statistically defined words 10 min after familiarization with an Italian corpus. Eight-month-old English-learning infants were familiarized with Italian sentences that contained 4 embedded target words—2 words had high internal TP (HTP, TP = 1.0) and 2 had low TP (LTP, TP = .33)—and were tested on their ability to discriminate HTP from LTP words using the Headturn Preference Procedure. When tested after a 10-min delay, infants failed to discriminate HTP from LTP words, suggesting that memory for statistical information likely decays over even short delays (Experiment 1). Experiments 2–4 were designed to test whether experience with isolated words selectively reinforces memory for statistically defined (i.e., HTP) words. When 8-month-olds were given additional experience with isolated tokens of both HTP and LTP words immediately after familiarization, they looked significantly longer on HTP than LTP test trials 10 min later. Although initial representations of statistically defined words may be fragile, our results suggest that experience with isolated words may reinforce the output of statistical learning by helping infants create more robust memories for words with strong versus weak co-occurrence statistics.

Studying audience effects in animals: what we can learn from human language research

a Department of Psychology, University of Tennessee, Knoxville, TN, U.S.A. b National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, TN, U.S.A. c ASU-SFI Center for Biosocial Complex Systems, Arizona State University, Tempe, AZ, U.S.A. d Santa Fe Institute, Santa Fe, NM, U.S.A. e Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, U.S.A. f NeuroNET Research Center, University of Tennessee, Knoxville, TN, U.S.A.

A cross‐language study of the influence of duration and intensity on perception of lexical stress

The present study examines perceived lexical stress across five languages which differ in their prosodic characteristics: English, French, German, Japanese, and Turkish. Native speakers from each language were presented with a two‐syllable nonsense word, (/bibi/), and were asked to judge whether the first or second syllable was more prominent. The relative durations and intensities of the two syllables were varied orthogonally across ranges, which were determined on the basis of analyses of natural utterances from the five languages. The key issue addressed is whether judgment of syllable prominence is cross‐linguistically invariant or dependent on exposure to language‐specific lexical stress patterns. [Work supported by NIDCD.]

Intersecting Constraints on Label Learning: Effects of Age, Label Properties, and Referential Context

ABSTRACT This research investigates the development of constraints in word learning. Previous experiments have shown that as infants gain more knowledge of native language structure, they become more selective about the forms that they accept as labels. However, the developmental pattern exhibited depends greatly on the way that infants are introduced to the labels and tested. In a series of experiments, we examined how providing referential context in the form of familiar objects and familiar object names affects how infants learn labels that they would otherwise reject, nonspeech sounds. We found evidence of the development of intersecting constraints: Younger infants (14-month-olds) were more open to learning nonspeech tone labels than older infants (19-month-olds), and younger infants were more open to the influence of referential context. These findings suggest that infants form expectations about labels and labeling contexts as they become more sophisticated learners.