Acoustic markers of prominence influence infants' and adults' segmentation of speech sequences

Two experiments investigated the way acoustic markers of prominence influence the grouping of speech sequences by adults and 7-month-old infants. In the first experiment, adults were familiarized with and asked to memorize sequences of adjacent syllables that alternated in either pitch or duration. During the test phase, participants heard pairs of syllables with constant pitch and duration and were asked whether the syllables had appeared adjacently during familiarization. Adults were better at remembering pairs of syllables that during familiarization had short syllables preceding long syllables, or high-pitched syllables preceding low-pitched syllables. In the second experiment, infants were familiarized and tested with similar stimuli as in the first experiment, and their preference for pairs of syllables was accessed using the head-turn preference paradigm.When familiarized with syllables alternating in pitch, infants showed a preference to listen to pairs of syllables that had high pitch in the first syllable. However, no preference was found when the familiarization stream alternated in duration. It is proposed that these perceptual biases help infants and adults find linguistic units in the continuous speech stream.While the bias for grouping based on pitch appears early in development, biases for durational grouping might rely on more extensive linguistic experience

Learning phonemic vowel length from naturalistic recordings of Japanese infant-directed speech.

In Japanese, vowel duration can distinguish the meaning of words. In order for infants to learn this phonemic contrast using simple distributional analyses, there should be reliable differences in the duration of short and long vowels, and the frequency distribution of vowels must make these differences salient enough in the input. In this study, we evaluate these requirements of phonemic learning by analyzing the duration of vowels from over 11 hours of Japanese infant-directed speech. We found that long vowels are substantially longer than short vowels in the input directed to infants, for each of the five oral vowels. However, we also found that learning phonemic length from the overall distribution of vowel duration is not going to be easy for a simple distributional learner, because of the large base-rate effect (i.e., 94% of vowels are short), and because of the many factors that influence vowel duration (e.g., intonational phrase boundaries, word boundaries, and vowel height). Therefore, a successful learner would need to take into account additional factors such as prosodic and lexical cues in order to discover that duration can contrast the meaning of words in Japanese. These findings highlight the importance of taking into account the naturalistic distributions of lexicons and acoustic cues when modeling early phonemic learning

Category formation and the role of spectral quality in the perception and production of English front vowels

This study aimed at comparing the perception and production of English front vowels by 17 proficient Brazilian speakers of English as a second language (L2) and 6 native speakers of American English. Towards this end, three experiments were carried out: (i) a production test measuring the first two formants of the participants ’ English front vowels, (ii) an oddity discrimination test investigating the formation of vowel categories, and (iii) a discrimination test with synthetic stimuli which assessed the participants ’ reliance on spectral quality when perceiving English vowels. The results of these experiments suggest a strong relationship between L2 vowel perception and production, since the vowel pairs which were produced with similar formant values by the Brazilian participants were also poorly discriminated in the two perception tests. In addition, the findings suggest that vowel perception might precede vowel production, as high rates on the discrimination of vowel pairs on both perception tests were a prerequisite for differentiating the same two vowels on the production test. Lastly, some Brazilian participants obtained native-like scores on the category formation test without manifesting native-like reliance on spectral quality, indicating that other acoustic cues, such as vowel duration, might be playing a role in their perception of English vowels. Index Terms: vowel perception, vowel production, English 1

The frequency distribution of vowel duration in the present Japanese IDS corpus.

<p>Ninety-four percent of the vowels in our corpus are short, and there is complete overlap in the distribution of short and long vowels. This kind of input is problematic for simple distributional learning models.</p

Mean duration of short and long vowels in the present Japanese IDS corpus.

<p>The difference in duration between short and long vowels is reliable and the effect size is large. The error bars represent the standard error of the mean for each vowel across participants.</p

Memory in the Neonate Brain

Background: The capacity to memorize speech sounds is crucial for language acquisition. Newborn human infants can discriminate phonetic contrasts and extract rhythm, prosodic information, and simple regularities from speech. Yet, there is scarce evidence that infants can recognize common words from the surrounding language before four months of age. Methodology/Principal Findings: We studied one hundred and twelve 1-5 day-old infants, using functional near-infrared spectroscopy (fNIRS). We found that newborns tested with a novel bisyllabic word show greater hemodynamic brain response than newborns tested with a familiar bisyllabic word. We showed that newborns recognize the familiar word after two minutes of silence or after hearing music, but not after hearing a different word. Conclusions/Significance: The data show that retroactive interference is an important cause of forgetting in the early stages of language acquisition. Moreover, because neonates forget words in the presence of some –but not all – sounds, the results indicate that the interference phenomenon that causes forgetting is selective

OxyHb changes from the last familiarization block to the first test block (Studies 2 and 3).

<p><b>A.</b> When the 2-minute pause was filled with music, channels in both hemispheres showed a decrement in the concentration of oxyHb from the familiarization to the test in the Same-word condition, and an increment in the Novel-word condition. <b>B.</b> There were no significant changes in oxyHb concentration from the familiarization to the test phases when the interval was filled with speech stimuli.</p

OxyHb changes from the last familiarization block to the first test block (Study 1).

<p>Channels bilaterally located in frontal, temporal and parietal areas show a decrease in the concentration of oxyHb when neonates hear the same word before and after the pause (white bar). In contrast, when neonates are confronted with a novel word in the test (black bar) the concentration from the familiarization phase to the test increases. Colored ellipses on the schematic neonate brain indicate the localization of the channels included in the areas of interest.</p

Experimental paradigm and results.

<p><b>A.</b> Schematic diagrams of the procedure used in the experiments. During the familiarization phase, all the neonates were presented with 10 blocks composed of 6 identical words. A period of silence of varying duration (from 25s to 35s) followed each block. In the test, 5 blocks of the same word heard during familiarization were presented to half of the neonates while the other half heard a novel word. In Study 1, a silent 2-minute interval intervened between familiarization and test. In studies 2 and 3, the silent interval was filled by music (Study 2) or speech stimuli (Study 3). <b>B-C-D)</b> Time courses of the relative hemodynamic changes averaged across all the channels and subjects per group. The dashed line indicates the time series for the group that heard the same word before and after the pause; the continued line represents the group that heard a novel word in the test. Error bars indicate standard errors. The x-axis shows number of blocks; in the y-axis the changes in concentration of Oxy-hemoglobin in mmol*mm is displayed. The neonates who heard a novel word after a silent period showed greater cortical Oxy-Hb concentration changes in the test than neonates who heard the same word before and after the silent pause. The presence of speech stimuli during the interval affects recognition memory in neonates. No interference was found when music was presented during the interval (*, <i>p</i><0.01; **, <i>p</i><0.0001).</p