Effects of Contingent Maternal Imitation vs. Contingent Motherese Speech on Infant Canonical Babbling

Maternal vocal stimulation plays a vital role in infants’ language acquisition. Contingent maternal imitation and contingent motherese speech were used in an alternating sequence as reinforcers to a 12 month-old infant’s canonical babbling. Both vocal contingencies function as reinforcers; however, motherese speech produced the highest frequency of canonical babbling. In the past three decades, the study of infant vocal development has yielded a deeper understanding of the emerging language in children (Oller, Eilers, Neal, & Schwartz, 1999). Early infant vocalization, starting as early as three weeks after birth, are precursors to speech. The sounds of the infant develop systematically and show a maturation of speech even before the child utters a single word. This knowledge has motivated research to identify infants who may be at risk of developing language delays. Research on older infants’ speech, however, is less conclusive and less common than studies with younger infants (McRoberts, McDonough, & Lakusta, 2009). Our programmatic research has shown that the early sounds produced by infants at 3-months elicit a response in adults (Pelaez, Virues-Ortega, & Gewirtz, in press). It is widely recognized that the acquisition of language is facilitated by a special manner in which adults speak to babies and toddlers, called baby-talk, motherese, or infant-directed (ID) speech (Falk, 2004). ID is particularly recognizable in the tone of voice the adults use; it is a type of sing-song way adults commonly use to communicate with young children. This type of speech is also commonly accompanied with visual interaction, gestures, and touch. For example, a mother speaking to her 5 month-old infant might use short sentences, a high pitch, exaggerated intonation, raised eye-brows, and a smile, while asking her baby how he is doing today. A universalist hypothesis states that ID speech may even contribute to initial infant emotional regulation, then to socialization, and finally to the acquisition of speech in a sequential, ageappropriate manner (Falk, 2004). This research examined the reinforcing effects of two maternal vocal topographies (maternal imitation and motherese speech) on infant vocalization (canonical babbling). The purpose of this research was to find out which type of response is most effective in increasing the frequency of babbling in a 12 month-old infant. We know that children’s earliest communication is an attempt to share and obtain information (Golinkoff, 1993) and that infants progressively expand their ability to communicate with others by coordinating behaviors from different expressive modalities, such as gaze, facial expressions, and vocalizations (Lin & Green, 2009). Moreover, infant speech screening procedures can help identify infants who are at risk of speech and language-related disorders (Oller et al., 1999), such as language-based learning disabilities, autism spectrum disorders, and speech delays among others. Oller et al. (1999) propose 4 stages in infant vocal development. The phonotation stage, producing quasivowels, is apparent in the first two months of life. In the second stage, primitive articulation stage, usually apparent at 2-3 months of age, infants produce sounds called cooing. In the third stage, called the expansion stage, infants produce full-like vowel sounds. Finally, in