Language Origins Viewed in Spontaneous and Interactive Vocal Rates of Human and Bonobo Infants.

From the first months of life, human infants produce "protophones," speech-like, non-cry sounds, presumed absent, or only minimally present in other apes. But there have been no direct quantitative comparisons to support this presumption. In addition, by 2 months, human infants show sustained face-to-face interaction using protophones, a pattern thought also absent or very limited in other apes, but again, without quantitative comparison. Such comparison should provide evidence relevant to determining foundations of language, since substantially flexible vocalization, the inclination to explore vocalization, and the ability to interact socially by means of vocalization are foundations for language. Here we quantitatively compare data on vocalization rates in three captive bonobo (Pan paniscus) mother-infant pairs with various sources of data from our laboratories on human infant vocalization. Both humans and bonobos produced distress sounds (cries/screams) and laughter. The bonobo infants also produced sounds that were neither screams nor laughs and that showed acoustic similarities to the human protophones. These protophone-like sounds confirm that bonobo infants share with humans the capacity to produce vocalizations that appear foundational for language. Still, there were dramatic differences between the species in both quantity and function of the protophone and protophone-like sounds. The bonobo protophone-like sounds were far less frequent than the human protophones, and the human protophones were far less likely to be interpreted as complaints and more likely as vocal play. Moreover, we found extensive vocal interaction between human infants and mothers, but no vocal interaction in the bonobo mother-infant pairs-while bonobo mothers were physically responsive to their infants, we observed no case of a bonobo mother vocalization directed to her infant. Our cross-species comparison focuses on low- and moderate-arousal circumstances because we reason the roots of language entail vocalization not triggered by excitement, for example, during fighting or intense play. Language appears to be founded in flexible vocalization, used to regulate comfortable social interaction, to share variable affective states at various levels of arousal, and to explore vocalization itself.

Consonant Acquisition in Young Cochlear Implant Recipients and Their Typically Developing Peers.

PURPOSE: Consonant acquisition was examined in 13 young cochlear implant (CI) recipients and 11 typically developing (TD) children. METHOD: A longitudinal research design was implemented to determine the rate and nature of consonant acquisition during the first 2 years of robust hearing experience. Twenty-minute adult-child (typically a parent) interactions were video and audio recorded at 3-month intervals following implantation until 24 months of robust hearing experience was achieved. TD children were similarly recorded between 6 and 24 months of age. Consonants that were produced twice within a 50-utterance sample were considered "established" within a child's consonant inventory. RESULTS: Although the groups showed similar trajectories, the CI group produced larger consonant inventories than the TD group at each interval except for 21 and 24 months. A majority of children with CIs also showed more rapid acquisition of consonants and more diverse consonant inventories than TD children. CONCLUSIONS: These results suggest that early auditory deprivation does not significantly affect consonant acquisition for most CI recipients. Tracking early consonant development appears to be a useful way to assess the effectiveness of cochlear implantation in young recipients.

Early gesture, early vocabulary, and risk of language impairment in preschoolers.

BACKGROUND: Gesture precedes vocabulary development and may be an early marker of later language impairment. AIMS: Using data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development, this study examined the contribution of children's (N=1064) early gestures and early vocabularies to their risk of language impairment in preschool years. METHODS AND PROCEDURES: At age 15 months, maternal reports on children's use of gestures and vocabulary comprehension and production skills were measured using the MacArthur Communicative Development Inventories. At age 3 and 4.5 years, children's language skills were assessed using the Reynell Developmental Language Scale and Preschool Language Scale-3, respectively. OUTCOMES AND RESULTS: After controlling for child, maternal, and family sociodemographic factors, children at later risk for language impairment were found to exhibit significantly less early gesture use and vocabulary skills relative to their typically developing peers. Early use of gestures was also significantly correlated with early vocabulary skills. CONCLUSIONS AND IMPLICATIONS: The effect of early gesture on children's later risk of language impairment was indirect and mediated by early vocabulary production. Early gesture may have the potential to serve as an early diagnostic tool and play a role in early intervention.

Volubility of the human infant: Effects of parental interaction (or lack of it).

Although parental volubility, or amount of talk, has received considerable recent attention, infant volubility has received comparatively little attention despite its potential significance for communicative risk status and later linguistic and cognitive outcomes. Volubility of 16 typically developing infants from 2 to 11 months of age was longitudinally investigated in the present study across three social circumstances: parent talking to infant, parent not talking to infant and parent talking to interviewer while the infant was in the room. Results indicated that volubility was least in the Interview circumstance. There were no significant differences in volubility between the parent Talk and No Talk circumstances. Volubility was found to reduce with age. These results suggest that infants vocalise in a variety of circumstances, even when no one talks to or interacts with them. The presence of a stranger or perhaps overhearing adults speaking to each other, however, may significantly reduce infant volubility.

Effects of Parental Interaction on Infant Vocalization Rate, Variability and Vocal Type.

Examination of infant vocalization patterns across interactive and noninteractive contexts may facilitate better understanding of early communication development. In the current study, with 24 infant-parent dyads, infant volubility increased significantly when parent interaction ceased (presenting a "still face," or SF) after a period of normal interaction ("face-to-face," or FF). Infant volubility continued at the higher rate than in FF when the parent re-engaged ("reunion," or RE). Additionally, during SF, the variability in volubility across infants decreased, suggesting the infants adopted relatively similar rates of vocalization to re-engage the parent. The pattern of increasing volubility in SF was seen across all of the most common speech-like vocal types of the first half-year of life (e.g., full vowels, quasivowels, squeals, growls). Parent and infant volubility levels were not significantly correlated. The findings suggest that by six months of age infants have learned that their vocalizations have social value and that changes in volubility can affect parental engagement.

Relationships between vocalization forms and functions in infancy: preliminary implications for early communicative assessment and intervention.

PURPOSE: This preliminary study explored relationships between form and function in prelinguistic vocalizations to increase our understanding of early communicative development and to provide potential clinical implications for early communicative assessment and intervention. METHOD: Twenty typically developing infants-5 infants in each of 4 age groups, from 3 to 20 months of age-were included. Vocalizations from these infants had previously been categorized for their form (Nathani, Ertmer, & Stark, 2006) and function (Stark, Bernstein, & Demorest, 1993) characteristics. In the present study, cross-classification tabulations between form and function were conducted to examine relationships between vocalization types and their apparent uses. RESULTS: As anticipated, earlier developing forms were mostly associated with earlier developing functions, and later developing forms were mostly associated with later developing functions. However, there were some exceptions such that some forms were associated with a variety of functions, and vice versa. CONCLUSIONS: The results suggest that some forms are more tightly coupled to function than others in the prelinguistic and early linguistic period. Preliminary implications for developmental theory, future research, and clinical applications are discussed. Larger, longitudinal studies with typical and atypical populations and stricter methodological controls are needed to validate these findings.

Effects of social games on infant vocalizations*.

The aim of the present study was to examine the contextual effects of social games on prelinguistic vocalizations. The two main goals were to (1) investigate the functions of vocalizations as symptoms of affective arousal and symbols of social understanding, and (2) explore form-function (de)coupling relations between vocalization types and game contexts. Seventy-one six-month-olds and sixty-four twelve-month-olds played with their mothers in normal and perturbed tickle and peek-a-boo games. The effects of infant age, game, game climax, and game perturbation on the frequency and types of infant vocalizations were examined. Results showed twelve-month-olds vocalized more mature canonical syllables during peek-a-boo and more primitive quasi-resonant nuclei during tickle than six-month-olds. Six- and twelve-month-olds increased their vocalizations from the set-up to climax during peek-a-boo, but they did not show such an increase during tickle. Findings support the symptom function of prelinguistic vocalizations reflecting affective arousal and the prevalence of form-function decoupling during the first year of life.

Fundamental frequency development in typically developing infants and infants with severe-to-profound hearing loss.

Little research has been conducted on the development of suprasegmental characteristics of vocalizations in typically developing infants (TDI) and the role of audition in the development of these characteristics. The purpose of the present study was to examine the longitudinal development of fundamental frequency (F(0)) in eight TDI and eight infants with severe-to-profound hearing loss matched for level of vocal development. Results revealed no significant changes in F(0) with advances in pre-language vocal development for TDI. Infants with hearing loss, however, showed a statistically reliable higher variability of F(0) than TDI, when age was accounted for as a covariate. The results suggest development of F(0) may be strongly influenced by audition.

Prelinguistic Vocal Development in Infants with Typical Hearing and Infants with Severe-to-Profound Hearing Loss.

Delays in the onset of canonical babbling with hearing loss are extensively documented. Relatively little is known about other aspects of prelinguistic vocal development and hearing loss. Eight infants with typical hearing and eight with severe-to-profound hearing loss were matched with regard to a significant vocal development milestone, the onset of canonical babbling, and were examined at three points in time: before, at, and after the onset of canonical babbling. No differences in volubility were noted between the two infant groups. Growth in canonical babbling appeared to be slower for infants with hearing loss than infants with typical hearing. Glottal and glide production was similar in both groups. The results add to a body of information delineating aspects of prelinguistic vocal development that seem to differ or to be similar in infants with hearing loss compared to infants with typical hearing.