Social role in infant’s language development. In this

Social cognition can be defined as “the study of the mental processes involved in perceiving, attending to, remembering, thinking about, and making sense of the people in our social world” (Moskowitz, 2004). Several distinctive abilities of social cognition include theory of mind (TOM), imitation, gaze following and social learning. These mechanisms form the basis of social behaviour and culture (Fitch, Huber and Bugnyar, 2010). Language allows us to express an arbitrary thought as a signal, and conversely, a signal as a thought. Language development starts with producing a wide variety of pre-linguistic vocalisations that contain the adult speech’s infraphonological features (Oller, 2000). There have been a few studies on a possible social mechanism of language development, but it has not yet been focused on because language production was considered to be linked to internal maturational systems rather than environmental influences (Bloom, 1993; Kent, 1981; Lenneberg, 1967). However, Gros-Louis et al., (2006) recently argued that behavioural responses of a social companion to an infant’s pre-linguistic vocalisations can encourage the production of particular vocalisations. Clark (1987) and Macnamara (1972) also suggested that children require advanced social cognition to acquire language because complex “mind-reading” abilities are essential to infer meanings behind words and communicate realistically. Up until lately, the only suggested system of vocal development was imitation according to Papousek and Papousek in 1989. While infants can imitate various acoustic characteristics of adult speech, and that imitation can provide them with incidental reinforcement of certain sounds, a study on vocal development in other species shows that imitation only has a limited role. Instead, social interactions and a social partner’s responsiveness encourage an infant’s vocal development through influencing extemporary speech and introduction of new sounds (Snowdon and Hausberger, 1997). Thus, it is suggested that a more general process through social interactions may also play an important role in infant’s language development. In this essay, several studies providing evidence for this mechanism will be introduced and discussed. Several researchers such as Goldstein, King and West (2003) suggested evidence for this mechanism from their experiment on mothers’ contingent responses to their infant’s vocalisations. In their study, thirty infants (mean age, 8 months and 14 days) and their mothers were engaged in two 30-minute plays. Half of the mothers, the contingent group, were required to respond immediately to their own infants’ vocalisations with non-social, vocal reactions such as smiling, touching and moving closer to their child. The other half of the mothers, the control group, were asked to react depending on response schedules of the contingent group’s mothers. To explore the role of contingency in vocal development, the timing of mothers’ responsiveness was manipulated in the second play session. The result revealed that infants who received contingent social feedback on their vocalisations, compared to infants who received social feedback regardless of when they produced vocalisations, generated more developmentally advanced vocalisations during both manipulation of maternal response and without manipulation. However, as mothers were instructed to respond, and reacted to every form of vocalisations regardless of their quality, it should be noted that it is not clear whether mothers respond consistently and predictably during everyday interactions as well. Hsu, Fogel and Messinger (2001) revealed similar results in their studies on unstructured infant-mother interactions. Infants generated more syllabic and speech-like vocalisations when they received social feedback such as smiling and eye contact from their mothers. This result shows that infants seem to be sensitive to other kinds of maternal feedback since mothers’ responses were not imitative in this study. Also, Locke (1996) argued that infants’ pre-linguistic sounds could evoke production of proximate sounds from parents, which leads them to encourage infants’ communicative development. From caregivers’ reactions, infants seem to learn the correlation between the production of particular sounds and following interactions with caregivers. Moreover, Bruner (1977) and Tomasello (1992) suggested that caregivers’ social feedback and early conversation seem to support infants’ language learning by being informed about objects and activities which are of their interests and attention. A number of studies on adult perception of infant vocalisations show that adults differentiate them from tracking prominent characteristics. According to Oller, Eilers and Basiner (2001), when infants start to generate their first well-produced consonant-vowel sounds, caregivers can identify these vocalisations. Studies on maternal responses during social interactions by Tamis-LeMonda, Bornstein and Baumwell (2001) suggested that mothers produce a wide range of feedback to infants’ vocal and social behaviours. Because the parents can distinguish different vocal forms and produce different proximate responses, maternal responses seem to certainly play a role in an infant’s language development. In addition, a study on vocalisation in infants with Autism Spectrum Disorder (ASD), who lack social interactions showed they do not have functional spoken language, which supports this social mechanism in language development. In this study, researchers investigated production of canonical babbling in infants with ASD and typically developing infants. It was well established that evaluation of early vocal behaviours in typically developing infants is critical to ordinary vocal development. Production of canonical syllables is a critical achievement in the development of spoken language and delayed emergence has been indicated to be predictive of significant communication impairment. Typically developing infants showed the onset of this babbling by no later than 10 months (Oller, 1980). Even infants with Down syndrome generally show ordinary ages of onset, in spite of a detectable delay of a month or more (Lynch et al., 1995). However, according to Oller et al. (2010), young children with ASD (16-48 months) showed low rates in production of canonical syllable compared to typically developing infants. Furthermore, twenty four infants at high-risk for ASD since they had siblings with ASD, generated significantly lower mean ratios of canonical babbling (measured as canonical syllables by every speech-like vocalisations) compared with 9-month old infants at low risk for ASD, but there were no significant findings with 12-month old infants. Similarly, infants with ASD showed significantly less total vocalisations compared to typically developing infants. (Patten et al., 2014)