Vocabulary Outcomes for 5-Year-Old Children Who Are Deaf or Hard of Hearing: Impact of Age at Enrollment in Specialized Early Intervention.

The aims of this study were to examine vocabulary scores of 5-year-old children who are deaf or hard of hearing (DHH), as well as the impact of early enrollment in specialized intervention on vocabulary outcomes. Receptive and expressive vocabulary scores were analyzed for 342 five-year-old children who are DHH enrolled in specialized listening and spoken language intervention programs. Regression analyses were utilized to examine the effects of age at enrollment on vocabulary outcomes. Overall, participants achieved scores within normal test limits on receptive and expressive measures of vocabulary. Children who enrolled in intervention prior to 28 months of age had better vocabulary skills at 5 years old. The findings support that children who are DHH can understand and produce vocabulary at skill levels commensurate with their typically hearing peers, regardless of severity of hearing loss. Results highlight the crucial impact of specialized programs on children's lexical readiness to participate in general education settings by kindergarten.

Infants' use of isolated and combined temporal cues in speech sound segregation.

This paper investigates infants' and adults' use of envelope cues and combined onset asynchrony and envelope cues in the segregation of concurrent vowels. Listeners heard superimposed vowel pairs consisting of two different vowels spoken by a male and a female talker and were trained to respond to one specific target vowel, either the male /u:/ or male /i:/. Vowel detection was measured in three conditions. In the baseline condition the two superimposed vowels had similar amplitude envelopes and synchronous onset. In the envelope cue condition, the amplitude envelopes of the two vowels differed. In the combined cue condition, both the onset time and amplitude envelopes of the two vowels differed. Seven-month-old infants' concurrent vowel segregation improved both with envelope and with combined onset asynchrony and envelope cues to the same extent as adults'. A preliminary investigation with 3-month-old infants suggested that neither envelope cues nor combined asynchrony and envelope cues improved their ability to detect the target vowel. Taken together, these results suggest that envelope and combined onset-asynchrony cues are available to infants as they attempt to process competing speech sounds, at least after 7 months of age.

Infants use onset asynchrony cues in auditory scene analysis.

This experiment investigated the effect of onset asynchrony on the segregation of concurrent vowels in infants and adults. Two vowels, randomly chosen from seven American-English vowels, were superimposed. Each vowel pair contained one vowel by a male and one by a female talker. A train of such vowel pairs was presented to listeners, who were trained to respond to the male target vowel /i:/ or /u:/. The ability to identify the target vowel was compared among three conditions: synchronous onset, 100-, and 200-ms onset asynchrony. Experiment 1 measured performance, in d', in 7-month-old infants and adults. Infants and adults performed better with asynchronous than synchronous vowel onset, regardless of asynchrony duration. Experiment 2 compared the proportion of 3-month-old infants achieving an 80% correct criterion with and without onset asynchrony. Significantly more infants reached criterion with asynchronous than with synchronous vowel onset. Asynchrony duration did not influence performance. These experiments show that infants, as young as 3 months old, benefit from onset asynchrony.

The Influence of Target and Masker Characteristics on Infants' and Adults' Detection of Speech.

Purpose: Several investigators have compared infants' detection of speech in speech and nonspeech maskers to evaluate developmental differences in masking. Such comparisons have produced contradictory results, possibly because each investigation used different stimuli. The current study examined target and masker effects on infants' and adults' detection of speech. Method: An observer-based procedure was used to compare infants' and adults' detection of the vowel /ʌ/ and the word "baby" in a 2-talker speech masker and matched speech-spectrum noise. The measure of performance was d'. A total of 43 7-month-old infants and 41 young adults were randomly assigned to 1 target-masker combination condition, and mean performance was compared across conditions at each age. Results: Adults' detection was influenced by an interaction between the target and the masker: Adults detected the vowel better in the 2-talker masker than in speech-spectrum noise but detected the word equally well in the 2 maskers. In contrast, infants detected both targets better in speech-spectrum noise than in the 2-talker masker. Conclusions: The relative effects of the masker on target detection by infants and adults depend on the target to be detected. Thus, conclusions drawn about differences between infants and adults in the mechanisms responsible for masking will depend on the stimuli. Standardization of speech stimuli in developmental research would help clarify the nature of infants' segregation difficulties. Supplemental Material: https://doi.org/10.23641/asha.5613139.

Infant pitch perception: Missing fundamental melody discrimination.

Although recent results show that 3-month-olds can discriminate complex tones by their missing fundamental, it is arguable whether they are discriminating on the basis of a perceived pitch. A defining characteristic of pitch is that it carries melodic information. This study investigated whether 3-month-olds, 7-month-olds, and adults can detect a change in a melody composed of missing fundamental complexes. Participants heard a seven-note melody and learned to respond to a change that violated the melodic contour. To ensure that participants were responding on the basis of pitch, the notes in the melody had missing fundamentals and varied in spectral content on each presentation. In experiment I, all melodies had the same absolute pitch, while in experiment II, the melodies were randomly transposed into one of three different keys on each presentation. Almost all participants learned to ignore the spectral changes and respond to the changed note of the melody in both experiments, strengthening the argument that complex tones elicit a sense of musical pitch in infants. These results provide evidence that complex pitch perception is functional by 3 months of age.