The purpose of this study was to examine changes in prelinguistic vocal productions during the first 20 months of life. Vocalizations were classified into 23 mutually exclusive and exhaustive types, and grouped into five ascending levels using the Stark Assessment of Early Vocal Development-Revised (SAEVD-R). Data from 30 typically developing infants, aged 0-20 months, show that older infants attained higher developmental levels on the SAEVD-R than younger infants. Infants 0-2, 3-5, and 6-8 months of age primarily produced vocalizations from Levels 1 (Reflexive), 2 (Control of Phonation), and 3 (Expansion). Infants 9-20 months of age also produced vocalizations from Level 4 (Basic Canonical Syllables). Only infants from 16-20 months of age produced Level 5 (Advanced Forms) vocalizations in significant quantities. The outcomes indicate that the SAEVD-R is a valuable instrument for evaluating prelinguistic vocal development.

The aim of this study was to examine prelinguistic vocal development in very young cochlear implant recipients. A prospective longitudinal research design was used to observe the sequence and time-course of vocal development in seven children who were implanted between 10 and 36 months of age. Speech samples were collected twice before implant activation and on a monthly basis thereafter for up to 2 years. Children's vocalizations were classified according to the levels of the Stark Assessment of Early Vocal Development-Revised (SAEVD-R; Nathani, Ertmer, & Stark, in press). The main findings were (a) six of seven children made advancements in vocal development after implantation, (b) children implanted between 12 and 36 months progressed through SAEVD-R levels in the predicted sequence whereas a child implanted at a younger age showed a different sequence, (c) milestones in vocal development were often achieved with fewer months of hearing experience than observed in typically developing infants and appeared to be influenced by age at implantation, and (d) in general, children implanted at younger ages completed vocal development at younger chronological ages than those implanted later in life. Clinical indicators of benefit from implant use were also identified. Keywords COCHLEAR IMPLANTS; CHILDREN; VOCAL DEVELOPMENT; SPEECH PRODUCTIONCochlear implants (CIs) have been shown to increase hearing sensitivity and improve auditory speech perception, speech production, and language ability in preschool and school-age children (e.g., ASHA, 2004;Blamey, Barry, & Jacq, 2001;Fryhauf-Bertschy, et al., 1997;Svirsky, Robbins, Kirk, Pisoni, & Miyamoto, 2000). Currently, however, little is known about the initial phases of speech development in very young implant recipients. Prelinguistic vocal development (hereafter referred to as "vocal development") is a process by which infants and toddlers produce increasingly diverse and adult-like utterances before they say words on a regular basis. For very young CI recipients, advancements in vocal development are likely to be among the first observable indications of increased hearing sensitivity and improved speech perception ability. That is, barring motoric, cognitive, or persistent technological problems, infants and toddlers with CIs should make progress in vocal development before words dominate their spoken output. Typical and Atypical Patterns of Vocal DevelopmentThe process of vocal development in typically developing infants and toddlers has been characterized as consisting of overlapping stages during which new vocalization types NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript emerge and become common (See Vihman, 1996 for review). For example, Stark (1980) proposed a five level model in which infants progressed from Reflexive sounds (e.g., cry and discomfort sounds) to Cooing (i.e., the voluntary productions of comfort sounds in the velar area), to Vocal Play (i.e., sounds showing increased control of phonation and art...

Infant vocal behaviors are extremely complex. Consequently, coding these behaviors is difficult and is typically associated with low reliability across observers. Various difficulties that arise when dealing with prelinguistic vocalizations, especially in the first 6 months of life, are outlined here. A proposed database of digitized infant vocalizations that illustrates strategies used to deal with these difficulties is then described. These strategies are based on theoretical infraphonological constructs, empirical observations, and information about the nature of mature phonological systems. Furthermore, the strategies are open-ended and can be modified as new information becomes available regarding infant vocal behaviors. At present, a preliminary database is available on the Web that illustrates some of these strategies. As the database is expanded, it is expected to provide a general framework for observers to categorize infant vocalizations and thereby enhance observer reliability.

Results provided further evidence of robustness of canonical babbling and indicated the need for a large parametric study evaluating effects of varying degrees of hearing loss and other risk factors on vocal development.

Final Syllable Lengthening (FSL) has been extensively examined in infant vocalizations in order to determine whether its basis is biological or learned. Findings suggest there may be a U-shaped developmental trajectory for FSL. The present study sought to verify this pattern and to determine whether vocal maturity and deafness influence FSL. Eight normally hearing infants, aged 0;3 to 1;0, and eight deaf infants, aged 0;8 to 4;0, were examined at three levels of prelinguistic vocal development: precanonical, canonical, and postcanonical. FSL was found at all three levels suggesting a biological basis for this phenomenon. Individual variability was, however, considerable. Reduction in the magnitude of FSL across the three sessions provided some support for a downward trend for FSL in infancy. Findings further indicated that auditory deprivation can significantly affect temporal aspects of infant speech production.