Full length articleWhat are the benefits of having a village? Effects of allomaternal care on communicative skills in early infancy
Introduction
During the late stages of infancy prior to toddlerhood, typically developing infants undergo developmental changes in both their language abilities and their energetic requirements. Before the age of two, typically developing infants are not yet considered highly competent communicators because they cannot yet string together words in such a way as to produce meaningful speech (Kuhl & Meltzoff, 1996). However, during this time, infants practice babbling, increase their vocabulary to a small range of words (Kuhl & Meltzoff, 1996; Oller et al., 2013), and develop the ability to share joint attention on subjects of interest (Tomasello & Rakoczy, 2003). Infants also experience energetic changes during this time, such that brain energy needs increase, fat deposits to support those needs begin to decrease, and mother’s milk alone no longer provides enough caloric support to meet these increasing energetic needs (Dettwyler, 1995; Humphrey, 2010; Kuzawa, 1998; Kuzawa et al., 2014). In humans, the dependency period is particularly prolonged to compensate for these issues (Aiello & Wells, 2002; Kuzawa et al., 2014; Leigh, 2012), and provide more time for the infant to be exposed to signal-rich experiences that appropriately shape brain development to support optimal conditioning to the cultural environment (DeVries, 1999; Greenough, Black, & Wallace, 1987; Hertzman & Boyce, 2010; Kolb, Mychasiuk, & Gibb, 2014). Allomaternal care (AMC, or supplemental care from individuals other than the mother) may be a key mechanism that supports optimal brain development during late infancy.
Notably, humans are unique in their universal expression of extensive cooperative care for infants via AMC, a trait that likely evolved relatively early on within the Homo lineage (e.g., Burkart, Hrdy, & van Schaik, 2009; Hawkes, 2014; Hrdy, 2007, 2009; Isler & van Schaik, 2012; Meehan, 2014; Meehan & Crittenden, 2016). AMC can come in the form of food sharing between allomaternal caregivers and infants, which can improve physical growth outcomes for infants by supplementing their energetic needs (Burkart et al., 2014; Isler & van Schaik, 2012, 2014), and historically researchers have focused efforts on exploring this benefit as physical growth and instances of food sharing are relatively easily measured. In fact, cooperative care through AMC and collaborative foraging (which enables food sharing) may have coevolved such that they produced similar selective pressures on the ontogeny of communicative behaviors associated with cooperation in both adults and infants (Tomasello & Gonzalez-Cabrera, 2017). Thus, AMC may also provide important developmental benefits for infant communicative abilities in addition to offsetting energetic needs, an outcome that has not yet been assessed. The current study seeks to understand how differences in exposure to AMC impact developmental outcomes within late infancy, providing a new avenue for understanding why humans continue to exhibit such extensive AMC across cultures.
Importantly, AMC can come in a variety of forms, including care from related and unrelated individuals, within both formal and informal settings. While care received in formal settings, such as childcare facilities and preschools, has been studied fairly intensively, care received in informal settings has received much less attention despite its high degree of prevalence across cultures (but see; Geoffroy et al., 2010; Hansen & Hawkes, 2009; Leach et al., 2008; NICHD Early Child Care Research Network, 2001). Particularly in non-Western cultures, but also in the West, AMC is frequently conducted by grandmothers and older siblings (e.g., Kramer & Veile, 2018; Sear, 2016). Grandparents have received attention for their ability to enable parents (mothers in particular) to get back to engaging in the workforce by providing free childcare in the home (e.g., Brady, 2016; Wheelock & Jones, 2002), with less focus on the potential developmental benefits the infant might receive from interacting with grandparents. Additionally, while older siblings are generally less recognized as caregivers in the United States, evolutionarily and in non-Western contexts, older siblings have played a very important role in providing significant levels of AMC (e.g., Kramer & Otárola-Castillo, 2015; Kramer & Veile, 2018), although the types of care and language input they use to communicate with infants may vary significantly from those provided by older individuals (e.g., Hoff, 2006). More research is needed to determine what ways informal care of all types might impact developmental outcomes by providing additional opportunities for language exposure.
If AMC does indeed help improve an infant’s communicative skills early on, this would not only translate to improvement in abilities to solicit care during early childhood (potentially improving survival outcomes), but also increased time to practice and perfect collaborative communicative skills for use in cooperative behaviors in later adulthood (potentially improving mate attraction and thus reproductive outcomes) (Tomasello & Gonzalez-Cabrera, 2017). Skills like shared attention and turn-taking are highly involved in cooperative activities, impacting a child’s ability to recruit attention and help from adults (i.e., solicit caregiving), as well as an adult’s abilities to coordinate social activities like recruiting help from other adults to share in the burden of care or participate in collaborative foraging (see Tomasello & Gonzalez-Cabrera, 2017). From the infant’s perspective, exposure to more AMC equates to exposure to more prospective communicative partners, potentially enhancing opportunities for infants to practice their skills of attracting attention and communicating needs to others (Aiello & Wells, 2002; Hawkes, 2014; Hrdy, 2007; Kolb et al., 2014; Nelson & Bloom, 1997).
In general, when infants interact with older children and adults, they have opportunities to learn and practice culturally-appropriate ways of communicating, and develop basic conversational skills like turn-taking and sharing attention (Bahrick & Lickliter, 2012; Feldman, Bamberger, & Kanat-Maymon, 2013; Greenough et al., 1987; Hedenbro & Rydelius, 2014; Hoff, 2006; Lewkowicz, 2012; Tomasello & Rakoczy, 2003). Since different types of caregivers are generally culturally-primed to interact with infants in distinct ways (Beebe & Steele, 2013; DiCarlo, Onwujuba, & Baumgartner, 2014; Fouts & Lamb, 2009; Jung & Fouts, 2011), different caregivers may also expose infants to slightly different communicative strategies. Previous research suggests that while joint actions and gestures such as pointing, showing, placing, and offering are universally expressed (regardless of culture) by children when interacting with adults at a young age (appearing between 8–15 months of age), the social environment helps determine the frequency and timing with which infants use these signals with caregivers (Salomo & Liszkowski, 2013). Generally speaking, between 12–18 months, children engage in a lot of joint attention behaviors, working to perfect behaviors like making eye-contact, alternating gaze, and pointing (Bakeman & Adamson, 1984; Carpenter, Nagell, & Tomasello, 1998; Tomasello, 1995). While most children have started to develop a small vocabulary of words by 15 months, generally only after 18 months do children become increasingly reliant on verbal communication (Bakeman & Adamson, 1984; Carpenter et al., 1998; Tomasello, 1995). Heightened AMC could be viewed as creating a specific type of social environment which provides opportunities for infants to gain increased exposure to culturally appropriate use of gestural (and verbal) communicative skills by increasing the number of potential signalers with which the infant can practice these skills.
Therefore, AMC potentially increases exposure to more varied stimuli and sensory experiences, which enables the brain to develop neural pathways that allow the infant to better perceive, categorize, and respond to signals in a culturally-appropriate way (Kolb et al., 2014; Nelson & Bloom, 1997; Singer, 1995; Sterner et al., 2012). The current study seeks to illuminate whether there are measurable differences in infant use of communicative behaviors as predicted by exposure to AMC, such that infants exposed to more AMC utilize communicative behaviors at a higher frequency to generate shared attention during dyadic interactions. In addition to AMC measures, this study emphasizes the possible impact siblings might have on infant development, utilizing birth order as a measure of the number of sub-adult communicators present in the home that could play an important role in helping infants develop certain behaviors.
Section snippets
Overview
This study was approved by the University’s Institutional Review Board for Research Involving Human Subjects, and was conducted in accordance with APA ethical standards in the treatment of the study sample. Mothers and their typically developing infants were recruited to participate in this study between May 2017 and October 2018 in Tucson, Arizona. Following screening and informed consent, mothers responded to online questionnaires through Qualtrics (a secure software program) to provide
Results
Across the twelve communicative behaviors assessed using linear regression of null models followed by backward model selection, two outcomes were significantly predicted by Household AMC, two were significantly predicted by the child’s birth order (a proxy for sub-adult communicators present in the household), and the rest did not retain any significant AMC predictors within the best fitting models (Table 4). As this paper focuses on the effect of AMC on communicative outcomes, this section
AMC exposure influences communicative behavior
These results show that AMC exposure likely influences some communicative behaviors, and that these differences are due to AMC received in informal settings rather than formal childcare settings. There were no effects of attending formal childcare, regardless of facility type, suggesting that at least at this age, formal AMC may have little impact on the development of communicative behaviors. Instead, what differences were attributable to AMC are a result of exposure to caregivers within the
Conclusions
These results are indicative of interesting next steps required to better understand how AMC at the household level, particularly in terms of sibling dynamics, impacts the development of communicative behaviors during infancy. Some behaviors are impacted by Household AMC, however, these relations are not in a uniform direction. Additionally, the effect of birth order (or the number of sub-adult communicators present in the house) on communicative behaviors is not uniform. Ultimately, this study
Funding
This work was supported by: the National Science Foundation [Award Number: BCS-1752542]; the University of Arizona’s (UA’s) School of Anthropology [W. & N. Sullivan Research Scholarship Fund and Reicker Endowment]; UA’s Confluencenter for Creative Inquiry; UA’s Social and Behavioral Sciences Research Institute; and UA’s Graduate and Professional Student Council.
Declaration of Competing Interest
None.
Acknowledgements
The author would like to extend special thanks to the participating mothers and children for their time, without which this study would not have been possible. The author also thanks Your Family’s Journey, Tucson Moms Group, Tucson Meet up Moms Group, and the many other local groups that shared recruitment information to potential participants. The author is grateful to the University of Arizona’s Frances McClelland Institute for Children, Youth, and Families, Dr. Andrea Romero, and Feliz Baca
References (88)
- et al.
Socioeconomic status and the developing brain
Trends in Cognitive Sciences
(2009) How contexts support and shape language development
Developmental Review
(2006)Weaning behaviour in human evolution
Seminars in Cell & Developmental Biology
(2010)- et al.
Allomaternal care, life history, and brain size evolution in mammals
Journal of Human Evolution
(2012) - et al.
When mothers need others: The impact of hominin life history evolution on cooperative breeding
Journal of Human Evolution
(2015) - et al.
Infant allocare in traditional societies
Physiology & Behavior
(2018) - et al.
How much is too much? The influence of preschool centers on children’s social and cognitive development
Economics of Education Review
(2007) Autism and pervasive developmental disorders
Pediatric Clinics of North America
(1993)- et al.
Individual differences in joint attention skill development in the second year, 1998
Infant Behavior & Development
(1998) Beyond the nuclear family: An evolutionary perspective on parenting
Current Opinion in Psychology
(2016)
Validity of the Center for Epidemiologic Studies Depression Scale—Revised (CESD-R): Pragmatic depression assessment in the general population
Psychiatry Research
Does child-care quality mediate associations between type of care and development?
Journal of Marriage and Family
Energetics and the evolution of the genus Homo
Annual Review of Anthropology
The role of intersensory redundancy in early perceptual, cognitive, and social development
Coordinating attention to people and objects in mother-infant and peer-infant interaction
Child Development
Bayley scales of infant and toddler development, third edition screening test manual
How does microanalysis of mother-infant communication inform maternal sensitivity and infant attachment?
Attachment & Human Development
Using parent questionnaires to assess neurodevelopment in former preterm infants: A validation study
Paediatric and Perinatal Epidemiology
Quantity counts: Amount of child care and children’s socioemotional development
Journal of Developmental & Behavioral Pediatrics
Are there long-term effects of early child care?
Child Development
Communicative skills in relation to gender, birth order, childcare and socioeconomic stats in 18-month-old children
Scandinavian Journal of Psychology
Socioeconomic status and child development
Annual Review of Psychology
Gluing, catching and connecting: How informal childcare strengthens single mothers’ employment trajectories
Work, Employment and Society
Chronicity, severity, and timing of maternal depressive symptoms: Relationships with child outcomes at age 5
Developmental Psychology
Siblings’ direct and indirect contributions to child development
Current Directions in Psychological Science
Child care quality and Dutch 2- and 3-year-olds’ socio-emotional outcomes: Does the amount of care matter?
Infant and Child Development
The evolutionary origin of human hyper-cooperation
Nature Communications
Cooperative breeding and human cognitive evolution
Evolutionary Anthropology: Issues, News, and Reviews
Social cognition, joint attention, and communicative competence from 9- to 15-months of age
Monographs for the Society for Research in Child Development, Serial No. 255
Behavioral phenotype of individuals with Down syndrome
Mental Retardation and Developmental Disabilities Research Reviews
A time to wean: The hominid blueprint for the natural age of weaning in modern human populations
Babies, brains and culture: Optimizing neurodevelopment on the savanna
Acta Pædiatrica
Infant communicative behaviors and maternal responsiveness
Child & Youth Care Forum
Child-care history, classroom composition, and children’s functioning in kindergarten
Psychological Science
Center for Epidemiologic Studies Depression Scale: Review and revision (CESD and CESD-R)
Parent-specific reciprocity from infancy to adolescence shapes children’s social competence and dialogical skills
Attachment & Human Development
Discovering statistics in R. E-book
Cultural and developmental variation in toddlers’ interactions with other children in two small-scale societies in Central Africa
International Journal of Developmental Science
Thinking in niches-sociocultural influences on cognitive development
Human Development
Atypical brain development: A conceptual framework for understanding developmental learning disabilities
Developmental Neuropsychology
Closing the gap in academic readiness and achievement: The role of early childcare
The Journal of Child Psychology and Psychiatry
Experience and brain development
Child Development
Early childcare and child development
Journal of Social Policy
Primate sociality to human cooperation why us and not them?
Human Nature
Cited by (2)
Social Competence and Its Related Factors in High School Students: A Cross-sectional Study
2023, Journal of Holistic Nursing and Midwifery