Denise Padden

Enhanced discriminability at the phonetic boundaries for the voicing feature in macaques

Discrimination of speech sounds from three computer-generated continua that ranged from voiced to voiceless syllables (/ba-pa/, /da-ta/, and ga-ha/ was tested with three macaques. The stimuli on each continuum varied in voice-onset time (VOT). Paris of stimuli that were equally different in VOT were chosen such that they were either within-category pairs (syllables given the same phonetic label by human listeners) or between-category paks (syllables given different phonetic labels by human listeners). Results demonstrated that discrimination performance was always best for between-category pairs of stimuli, thus replicating the “phoneme boundary effect” seen in adult listeners and in human infants as young as I month of age. The findings are discussed in terms of their specific impact on accounts of voicing perception in human listeners and in terms of their impact on discussions of the evolution of language.

Brain Responses to Words in 2-Year-Olds with Autism Predict Developmental Outcomes at Age 6

Autism Spectrum Disorder (ASD) is a developmental disability that affects social behavior and language acquisition. ASD exhibits great variability in outcomes, with some individuals remaining nonverbal and others exhibiting average or above average function. Cognitive ability contributes to heterogeneity in autism and serves as a modest predictor of later function. We show that a brain measure (event-related potentials, ERPs) of word processing in children with ASD, assessed at the age of 2 years (N = 24), is a broad and robust predictor of receptive language, cognitive ability, and adaptive behavior at ages 4 and 6 years, regardless of the form of intensive clinical treatment during the intervening years. The predictive strength of this brain measure increases over time, and exceeds the predictive strength of a measure of cognitive ability, used here for comparison. These findings have theoretical implications and may eventually lead to neural measures that allow early prediction of developmental outcomes as well as more individually tailored clinical interventions, with the potential for greater effectiveness in treating children with ASD.

ERPs to words correlate with behavioral measures in children with Autism Spectrum Disorder

Children with Autism Spectrum Disorder (ASD) participated in a research study that involved both electrophysiological and behavioral measures. Event related brain potentials (ERPs) were recorded during auditory presentation of known and unknown words. Behavioral measures of language/cognitive function and severity of autism symptoms were also collected at the time of ERP testing and again one year later. In general, higher functioning children with ASD exhibited more localized brain effects for differences between known and unknown words. Lower functioning children with ASD had more diffuse patterns of response to the different word classes and also exhibited a stronger right hemisphere lateralization. That is, they showed differences between known and unknown words at many electrode sites and larger differences in the right hemisphere. In addition, significant correlations were obtained between specific brain wave measurements for both known and unknown words and the various behavioral measures. Patterns of ERPs effectively predicted later behavioral scores.

The bilingual brain: A comparison of native and non‐native speech perception in monolingual and bilingual infants

Infants raised in monolingual families are equally good at native and non‐native speech discrimination early in life. By 12 months, performance on native speech has significantly improved while non‐native performance declines. We tested bilingual American infants at 7 and 11 months of age on native (/ta‐pa/) and non‐native (Mandarin affricate‐fricative) contrasts used in the monolingual tests. Phonetic discrimination was assessed using behavioral (conditioned head‐turn) and brain (event‐related potential) measures. The MacArthur Communicative Development Inventory estimated infants developing language skills at 14, 18, 24, and 30 months of age. The monolingual data [Kuhl et al., Language Learning and Development (2005)] demonstrated that at 7 months of age, infants native and non‐native speech perception skills predicted their later language development, but differentially. Better native phonetic perception predicted more rapid language development between 14 and 30 months, whereas better non‐native phone...

Effects of short‐term exposure to a foreign language on discrimination of a non‐native phonetic contrast: Convergent evidence from brain and behavioral tests

Studies in our laboratory demonstrate that between 6 and 12 months of age infants show a significant increase in the ability to discriminate native‐language phonetic contrasts and a decline in foreign‐language discrimination. The increase in performance on native‐language contrasts suggests a process of active learning rather than maintenance. In the present experiment, we tested whether the learning process infants engage in during the period between 6 and 12 months extends to a foreign language the infants had not previously heard. American infants at 9 months of age participated in a 12‐session language play group in which they heard a native speaker of Mandarin Chinese read, play, and talk to them. A control group was exposed to American English using the same books and toys. Both groups were subsequently tested on a Mandarin Chinese contrast using both behavioral and brain measures. The results demonstrate that infants exposed to Mandarin over a 4‐week period show significant discrimination of the Ma...

Assessment of the intelligibility and perceived quality of speech produced by text‐to‐speech engines

The intelligibility and quality of speech produced by current text‐to‐speech (TTS) engines was assessed using well‐established tests of speech intelligibility. TTS engines included Microsoft’s Whistler, AT&T’s Watson, and Elan Informatique’s ProVerbe. The speech intelligibility tests varied in complexity and in the degree to which syntax and lexical knowledge could aid perception. Stimuli included CVC words, semantically meaningful sentences, semantically anomalous sentences, and paragraphs representing different styles of discourse. Intelligibility was evaluated using transcription accuracy for isolated word and sentence items, as well as ratings of the clarity of articulation for word and paragraph items. Perceptual errors on word items also were analyzed by phoneme and word position (initial, medial, or final). Additional ratings were used to determine the perceived ‘‘naturalness’’ of meaningful sentences and paragraph items. Across levels of speech complexity, clear and consistent differences between ...

Speech discrimination by macaques: enhanced discrimination at the phonetic boundaries between speech‐sound categories

Discrimination of speech‐sound pairs drawn from a computer‐generated continuum in which syllables varied along the Place of Articulation phonetic feature (/bae, dae, gae/) was tested with macaques. The acoustic feature that was varied along the 15‐step continuum was the starting frequencies of the first and second formant transitions. Discrimination of stimulus pairs separated by two steps was tested along the entire continuum in a same‐different task. Results demonstrated that peaks in the discrimination functions occur for macaque listeners at the “phonetic boundaries” which separate the /b‐d/ and /d‐g/ phonetic categories for human listeners. This effect of greater discriminability at the phonetic boundaries in macaque listeners replicates that seen in human listeners as young as one month of age. The data demonstrate that the results previously obtained with nonhuman listeners on the voiced‐voiceless (/b‐p/, /d‐t/, /g‐k/) phonetic feature can be generalized to another phonetic feature; this finding is...