Social and endogenous infant vocalizations

Abstract

27 Research on infant vocal development is focused primarily on vocal interaction with caregivers, 28 where it appears to be largely assumed that infants vocalize mostly for the purpose of interaction. 29 A survey of both parents and non-parents indicated that public opinion conformed to the 30 expectation that infant vocalization is mostly socially interactive. However, we report that in 31 laboratory recordings of infants and their parents, the bulk of infant speech-like vocalizations 32 ("protophones") were directed toward no one, and instead appeared to be generated 33 endogenously in exploration of vocal abilities. The tendency to produce protophones without 34 directing them to others occurred both during periods when parents were instructed to interact 35 with their infants and during periods when parents were occupied with an interviewer, with the 36 infants in the room. The results emphasize the infant as an agent in vocal learning, not as a 37 passive recipient of vocal input.38 Keywords: Speech development 1 , Social interaction 2 , Illocutionary force 3 , Prelinguistic 39 communication 4 , Origin of language 5 , Language development 6 , Evolutionary-development 7 42 The study of vocal development has been dominated by the expectation that infants primarily 43 vocalize in a speech-like manner when they are in social engagement, an expectation suggesting 44 social interaction drives prelinguistic vocal development (1-6). Granted, social learning is 45 required in order for infants to acquire the language-specific syllables and phonemic elements 46 and the largely arbitrary pairings of words with meanings in languages. Thus, there can be no 47 doubt that social interaction plays a critical role in infant vocal learning and language 48 acquisition. Surprisingly, however, we know little about the extent to which infants actually 49 engage in directed vocal interaction using the speech-like sounds or "protophones" of infancy 50 (which include both canonical babbling and precanonical speech precursors in accord with the 51 terminology of Oller, 2000), as opposed to simply vocalizing playfully or exploratorily. The 52 proportion of infant protophones that are socially-directed has, to our knowledge, never been 53 previously quantified, so the extent to which infant protophone production may be primarily 54 endogenous rather than social is unknown.55 Even so, infant vocalization, especially in the context of social interaction, has been researched 56 for half a century (8-13). A social feedback loop has been posited to exist in infant and child 57 vocalization, and that loop has been thought to promote contingent infant vocalizations with 58 respect to caregiver vocalizations (14-17). Experimental studies in the still-face paradigm (18) 59 have shown that by 5-6 months of age, infants increase the rate of protophone production when 60 the parent disengages from an ongoing vocal interaction (19,20), suggesting infants by that age 61 seek to repair broken interactions with increased vocalization. SOCIAL AND NON...

Canonical babbling during vocal turn taking and independent vocal play

“…Higher CBRs will occur during segments with high TT compared to low TT, a prediction based on the existing literature showing positive effects of social interaction on infant vocal development [12,15,49], and 4. Higher CBRs will occur during segments with high VP compared to low VP, a prediction based on the growing body of evidence indicating high rates of endogenous vocal activity proposed to signal fitness to caregivers [21,24].…”

“…Infant protophones [2] are considered foundations for speech in that they manifest a capacity to produce phonation and other speech characteristics voluntarily, in the absence of external stimulation, as is required in speech. Such baby sounds can be seen as fitness signals, selected because they tend to elicit longterm investment from caregivers, required across the lengthy period of relative helplessness, or altriciality, of infant humans [8,21,26,27]. Parents throughout hominin history can be viewed as having implemented the selection of the infant trait of endogenous protophone production.…”

“…Contradicting the seemingly implicit assumption in child development literature that infant vocalizations are routinely produced during social interaction, several researchers have recently emphasized the role of intrinsic motivation in the development of emotional and cognitive systems, including those related to vocal development [22,23,34]. We previously showed that typically developing infants produce protophones (both canonical and precanonical) predominantly endogenously, that is, with no indication of social directivity [21]. Even in laboratory recordings, during periods when parents are instructed to seek social interaction with infants, most protophones (∼60%) appear not to be directed to them.…”

Reverse Engineering Language Acquisition with Child-Centered Long-Form Recordings

“…In this section, we turn to production, although we start by admitting that this line of research is a great deal less developed than the perception one, and it may take considerable time to make progress in this area. As with perception, the development of production involves learning mechanisms that are still the matter of active debate (Long et al 2020).…”

“…• The presence of both speech-like and non-speech-like vocalizations (Long et al 2020) • The increase in canonical vocalizations (having at least one adult-like consonant-vowel or vowel-consonant transition) with age (Cychosz et al 2021) • The appearance of meaningful utterances, starting with single words (de Boysson-Bardies and Vihman 1991) • The appearance and increased prevalence of word combinations (Braine and Bowerman 1976) Not only are all of these phenomena not currently within the scope of any extant model learners, but also the basic description of these phenomena in long-form recordings is rare. In fact, it is only recently that it was found that speech-like vocalizations are prevalent in long-form recordings even among newborns (Long et al 2020); and that the proportion of vocalizations containing canonical transitions appears to continually increase well beyond the first year of age, according to long-form data (Cychosz et al 2021). Information from long-form recordings on the other phases, namely the appearance of meaningful speech and of word combinations has been documented in only two studies (Casillas et al 2020b,a), both of which employed human annotation.…”