Abstract:

Speech-like vocalizations are sounds that resemble adult speech and are the precursor for subsequent language development. The current study explored the relationship between vocalizations and language in typically developing infants and young children with language disorders, specifically the quantity of vocalizations, phonological quality of vocalizations, and the communicative quality of vocalizations. The quantity of vocalizations, the total number of vocalizations, predicts expressive language, but inconsistently predicts receptive language development. The phonological quality of vocalizations is measured through four indicators, of which the proportion or frequency of vocalizations with a canonical syllable, consonant inventory and diversity of key consonants used in communication predict expressive language, while the age at canonical babbling onset inconsistently predicts age of word onset and expressive vocabulary size. The communicative quality of vocalizations, including the number of communication acts with a vocalization and proportion of communicative vocalizations, predicts expressive language.
Three mechanisms explain how speech-like vocalizations may predict future language ability: speech-like vocalizations provide the basis for language production, create optimal learning states for language learning, and promote socially contingent responses. The first mechanism emphasizes the foundations of speech-like vocalizations, i.e., they provide the phonological basis for early vocabulary and the functional flexibility for language. The second mechanism emphasizes the influence of speech-like vocalizations on children’s own language learning status, i.e., speech-like vocalizations indicate that the child is in an attentional state that facilitates learning, speech-like vocalizations help the child’s speech perception, and reflects the child’s motivation to actively participate in social interactions. The third mechanism emphasizes the social function of speech-like vocalizations, i.e., children elicit responses from social partners through speech-like vocalizations, which provide contingent, scaffolding support, and didactic information. All three mechanisms contribute to the transition of children’s speech-like vocalizations to language.
Many studies have investigated the correlation between speech-like vocalizations and language ability, and future studies may consider exploring the causal relationship between speech-like vocalizations and language development. For example, a speech-like vocalization intervention for children with language disorders could be used to examine its causal relationship with language. The relationship between language ability and speech-like vocalizations may be influenced by factors such as cognition, age and degree of impairment in children with language disorders, and the moderating effects of these factors may be investigated in the future. Different criteria for speech-like vocalization indicators and language testing methods may also influence this prediction, and controlling for the role of these two factors is one of the directions for future research. Future research could also investigate individual differences among children with language disorders, and explore if specific speech-like vocalizations of children with different language disorders are uniquely predictive of future language in order to better implement interventions. How the dynamic interaction between children’s speech-like vocalizations and social responses promotes their transition to language is another question worthy of exploration, especially the longitudinal exploration of children’s vocal development and social responses during interaction.

Key words: infants and toddlers, speech-like vocalizations, language development, language disorder