Jul 29 2020

How Infants Learn Language: Part II

Written By: Ellen A. Rhoades, Ed.S., LSLS Cert AVT

This is the second of a two-part article that focuses on infant-directed speech (IDS), also known as child-directed speech or caregiver talk.

What is infant-direct speech (IDS)? It’s a method of language development that uses simpler words, repetition, a higher range of pitch and slower rate of speaking to help a child learn to speak. IDS is an interactive dialogue accorded privileged status that neurobiologically promotes early speech processing and language development which is a good predictor for later academic success (Hirsh-Pasek & Golinkoff, 2019). IDS captures infants’ attention which, in turn, controls such finite cognitive resources as auditory memory, auditory perception, and language. Repeatedly securing the child’s attention is essential for statistical learning (Kalashnikova et al., 2018; Lindsay, 2020; Piazza et al., 2017; Romeo et al, 2018; Thiessen, 2017).

A caregiver can exploit the predictability of spoken words so that the child perceives what is heard with greater efficiency. The better the child’s predictability skills, the better the child will process or extract meaning from what is heard (Riecke, 2020). Young language learners, including those wearing hearing devices, seem to prefer and better attend to IDS than to adult-directed speech (Robertson, van Hapsburg & Hay, 2015; Wang, Bergeson & Houston, 2017; 2018).

Deviations and Exceptions to Infant-Directed Speech

Research findings show that IDS is an almost-universal way of talking to young language learners. Certain characteristics seem to be associated with greater language learning, e.g., the more caregivers repeat words, the more likely the child will comprehend those words at an early age (Schwab et al., 2018). While we know caregiver attachment and sensitivity are critical for babies, we know that IDS can strengthen the child-caregiver emotional bond as well as the child’s core cognitive skills of attention and memory.

Language, an essential part of child development that affects how we interact with other people, is a fundamental characteristic of culture. It is, however, important to remember that language ultimately depends on context–the situation in which one is placed at any given time. For example, among low-resource households, pragmatic caregivers’ child-directed speech can differ in several ways, e.g. different vocabulary composition with more commands rather than declaratives and requests (Kuchirko et al., 2020; Pace et al., 2017; Rosemberg et al., 2020).

How and when young children learn language varies from culture to culture. Perhaps this is most noticeable when comparing many children living in westernized, industrialized nations versus those living in remote agrarian communities. Some infants living in non-westernized families are not exposed to IDS; however, they may overhear language spoken in their respective communities. Their caregivers may not engage in “caregiver talk” until the children are toddlers or preschoolers. These typically hearing children learn language at a later age, primarily by socializing with their peers and older siblings until early adolescence (Cristia, 2019; Ochs & Scheiffelin, 2011).

Many child development models based on Western standards are too narrow. Age-based language learning milestones, then, might simply be considered artifacts of culture. However, this does not necessarily detract from the learnability properties of IDS (Adriaans, 2017; Ludusan et al, 2016). The child whose hearing loss is effectively and consistently amplified prior to three years of age is much more likely to learn listening and spoken language skills—particularly if caregivers diligently promote statistical learning and speech perception via IDS (Werker & Hensch, 2015).

As children engage in the language learning process, they become more adept at processing rapid “caregiver talk.” In other words, IDS is considered fluid in that it evolves with maturation. Age-related increases occur across the first two to three language learning years, modified according to caregiver sensitivity to each child’s developmental needs and preferences. For example, over the course of the first language learning year, there tends to be a decrease in some acoustic prominences, an increase in word diversity, and little to no changes in vowel hyperarticulation (Kalashnikova & Burnham, 2018; Liu, Tsao & Kuhl, 2009).

Characterizations of Infant-Directed Speech

A checklist of four categorical features that characterize IDS (see Figure 1) can be used for face-to-face or online observations of caregiver-child interactions. Service providers can use this checklist to note the presence or absence of specific characteristics within caregiver-child interactions, just as caregivers can refer to it as reminders for incorporating certain characteristics when communicating with language learning children. There are no age limits or milestones in this checklist, so it can be used with “late-identified children,” e.g., those who might be language delayed or whose hearing loss was identified beyond infancy.

Section A. Social Characteristics refers to those rhythmic, mutually responsive face-to-face nonverbal movements relevant to rhythmic “conversational duets” between caregiver and child. Infants’ social gazing is important for socio-emotional bonding with caregiver and for intentional communication. Indeed, the more turn-taking, the greater the effect on the child’s brain. These initially exaggerated exchanges are attention-getting on positive emotional, physical, and visual levels, and especially important for language learners with hearing loss (Addabbo et al., 2020; Azhari et al, 2020; Barrett et al, 2020; Cannon & Chatterjee, 2019; Dimitrova, 2020).

Section B. Prosodic Characteristics focuses on the acoustic landmarks of IDS, generally referred to as phonological simplifications. Word and phrase segmentation is perceptually salient. Acoustic boundaries are especially noticeable, i.e., there are longer pauses between words and phrases. Melodic content tends to be exaggerated during the first language learning year. This is particularly important for children recently provided with sufficient access to conversational sound, regardless of hearing device (Estes, 2014; Estes & Hurley, 2013; Leong, Kalashnikova & Goswami, 2017; Segal, Houston & Kishon-Rabin, 2016).

Section C. Structural Characteristics highlights those characteristics promoting lexical and morphosyntactical growth, otherwise known as vocabulary and grammar. “Caregiver talk” is repetitive, directed to and pertinent to the child’s activity at hand. Within the first few months of life, the home environment already begins shaping the child’s vocabulary. The lexical repertoire does not seem different when the dyad involves a young child with hearing loss. Over time, shorter utterances couching familiar or new words within simple sentences are gradually expanded, and more questions are added (Bergelson & Aslin, 2020; Newman, Rowe & Ratner, 2015; Schwab et al., 2018; Segal & Newman, 2015; Wang et al., 2020).

Section D. Content Characteristics focuses on those characteristics that signify caregiver awareness of the child’s evolving language needs. Children preferentially attend to spoken language at a manageable level of complexity. As their auditory attention improves, they may learn from overheard speech. Over time, IDS becomes more complex in both grammar and vocabulary. However, this necessitates caregiver flexibility; the inclusion of more abstract language with more rare-sophisticated words enables a transition toward adult-directed speech. Regardless of child’s chronological age, this evolution of IDS seems to occur until the child is linguistically competent, i.e., approximately three years (Foushee, Griffiths & Srinivasan, 2020; Kidd, Piantadosi & Aslin, 2014; Kucker, McMurray & Samuelson, 2020; Scott, McNeill & van Bysterveldt, 2020).

Issues to Consider with Infant-Directed Speech

Each caregiver-child dyad is uniquely complex. Families differ dramatically in structure, relationships, and adaptability (see review by Rhoades, 2017). In turn, family systems are affected by a host of environmental variables, including their expectation levels of the child with hearing loss (Ching & Wong, 2017; Hyde, Punch & Grimbeek, 2011; Verdon, 2020). It is difficult for one practitioner to provide effective interventions that will optimize caregiver-child exchanges for all types of family situations and issues.

In general, mid- to high-resource caregivers provide more positive affirmations and encouraging language than do resource-constrained caregivers, with the latter often providing more directive language. For example, resource-constrained caregivers may experience multiple stressors, so they often tell their babies what to do, using limited vocabulary, as opposed to describing what their babies are experiencing, with more advanced and varied vocabulary in a topic-continuing manner (e.g., Ramirez, Lytle & Kuhl, 2020). Income inequality is a growing problem across all nations (Odgers & Adler, 2018). Because such differences in “caregiver talk” have cascading effects, practitioners engaged in evidence-based coaching avoid passing judgment on other cultures while being effective agents for change (Kemp & Turnbull, 2014; Kolijn et al, 2020; Pellecchia et al, 2020; Romano & Schnurr, 2020).

For varied reasons, some families are hard to reach (Barr, Duncan & Dally, 2018; Boag-Munroe & Evangelou, 2012). Other families may be embedded in cultures beyond the ken of some practitioners (Vaughan et al., 2015). Aside from the child’s hearing loss and westernized caregivers, some issues may not be within the professional realm of early intervention (EI) or Listening and Spoken Language (LSL) service providers’ expertise (Cupples et al., 2018; Iffland & Neuner, 2020). Multiple issues can adversely influence caregiver-child interactions in significant ways (Erozkan, 2016; Gabrieli et al, 2020; Loeb et al., 2020; Toof, Wong & Devlin, 2020; Vogel et al, 2020).

It can be helpful to question the existence and extent of such mitigating factors. When caregiver-child exchanges seem compromised, it behooves practitioners to dig deeper, trying to understand those factors that shape caregivers’ interactions with their children. The expertise of specialized practitioners can inform interventions designed to promote IDS. Holistic interventions that cut across disciplines may be necessary for those families unable to demonstrate healthy ‘caregiver talk’ (Lorio et al., 2019; Rowe, 2018).

Child: 5 considerations

Are the child’s Hearing Age and Language-equivalency Age factored into the use of IDS?

Has the child experienced any pre-, peri- or post-natal medical/health trauma?

Does the child have sufficient and consistent acoustic accessibility in relative quiet?

Has the child experienced mistreatment, such as abuse or neglect?

Beyond hearing-related issues, does the child demonstrate developmental delays?

Caregiver: 5 considerations

Has the primary caregiver already established a secure attachment bond with the infant?

Does the caregiver generally demonstrate sensitivity in recognizing the child’s needs?

Does the caregiver respond appropriately and consistently to the child’s needs?

Is the caregiver in a stable positive mindset, free of post-partum depression?

Is the child’s hearing loss causing the parent to engage in excessive directive talk?

Family: 5 considerations

Does the child’s family have sufficient resources to promote the use of IDS?

Is the family size and composition amenable toward giving the child sufficient attention?

Is the household routines-based and are extraneous noises effectively managed?

Are family relationships supportive, stable, and free of mistreatment, abuse, or neglect?

Is the home conducive for verbal caregiver-child exchanges within a listening bubble?

Service provider/agency: 5 considerations

Has a therapeutic alliance been established between service provider and caregiver?

Does the service provider facilitate social components of language input via coaching’?

Has the service provider transmitted sufficient feedback and knowledge base to caregivers?

Does the service provider demonstrate appropriate guiding and scaffolding strategies?

Does the service provider’s agency provide flexibility in service delivery and positive support?

Minimizing the Effects of Hearing Loss on Learning

Beyond the use of IDS during the early language learning years, certain factors should be in place for children with hearing loss. Although oft-repeated, caregivers are reminded of two critical issues that should occur concurrently:

  1. Caregiver’s voicing features: Many children with hearing loss recognize their primary caregiver’s voice (Vongpaisal et al., 2019). However, when ‘caregiver talk’ is softly-spoken, it may be problematic for young language learners with hearing loss. So, it is important that the intensity level of a caregiver’s voice be robust enough for the child’s speech comprehension, i.e., at the average conversational level of approximately 60 dB sound pressure level (Boothroyd, 2021). Beyond the language learning years, there are data showing that the speaker’s voicing features tend to facilitate such cognitive capacities as working memory (Gudi-Mindermann et al., 2020). In short, it is to the child’s advantage to have each motivated caregiver develop the habit of speaking strongly and emotively.
  2. Child’s acoustic accessibility: Talking close to the infant’s microphone is a critical strategy for ensuring the clearest auditory signal (Ling & Ling, 1978; Wright, 1915). “Within earshot” is the distance over which speech sounds are most easily intelligible to listeners. Optimal listening conditions in a quiet room at a soft conversational level means talking within 3-6 inches or 15 cm from each child’s hearing device microphone (Rhoades, 2011). Remote microphone systems and telecoils are excellent hearing device accessories for when children become more mobile (Benitez-Barrera et al., 2020; Thompson et al., 2020). Otherwise, ‘caregiver talk’ should remain within the “listening bubble,” a 3-5 foot or 2 meter range of wherever the child with hearing loss is situated (Anderson, 2015; Droogendyk, 2015). Consistent and sufficient acoustic accessibility serves a dual purpose: to facilitate speech comprehension and to minimize listening effort as well as auditory fatigue.

While auditory experiences during the first year of life unquestionably facilitate the development of listening and spoken language, the value of later accessibility to sufficient sound should never be discounted. Assuming positive family support, ‘caregiver talk’ that facilitates attention and statistical learning can enable the late-identified child to learn spoken language. Beyond infancy, IDS is a critical language teaching tool for young preschoolers with hearing loss.

Author’s personal post scripts:

My congenital severe-profound bilateral deafness was not identified until I was two years of age. I remained essentially “languageless” until fit with a hearing aid a few months later. Across my remaining preschool years, my mother consistently employed IDS with strong, deep voicing features. By the time I entered first grade at 6 years of age, my hearing age and language age-equivalency were 4 years. Thereafter, language socialization with same-age peers across grade school proved critical.

At 50 years of age, I began traveling to Central and South America to give workshops. I wanted to re-learn Spanish. A Guatemalan friend came to my house and tried teaching me her native language, but I had great difficulty understanding her; she spoke so quickly and everything sounded the same. Finally, I told her to talk to me like I was a baby. She shifted gears and used IDS. Slower speech. Phrase boundaries. Emotion-laden words. Consonant clarity. Repetitive words. Simple sentences. Eureka! I understood her with relative ease. IDS worked for me as a language learning tool. 

REFERENCES

(For readers interested in the evidence underlying this broad and highly researched topic of IDS, care has been taken to avoid repeating those references listed in How Infants Learn, Part I)

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