The mountain stream of infant development

Abstract

Development is complex. It encompasses interacting domains, at multiple levels, across nested time scales. Embracing the complexity of development-while addressing the challenges inherent to studying infants-requires researchers to make tough decisions about what to study, why, how, where, and when. My own view is inspired by a developmental systems approach, and echoed in Esther Thelen's (2005) mountain stream metaphor. Like a river that carves its course, the active infant navigates the social and physical environment and generates rich inputs that propel learning and development. Drawing from my experiences, I offer some recommendations to guide research on infants. I encourage researchers to embrace discovery science; to observe infants in ecologically valid settings; to recognize the active and adaptive nature of infant behavior; to break down silos and consider the nonobvious; and to adopt full transparency in all aspects of research. I draw on cascading influences in infant play, language, and motor domains to illustrate the value of a bottom-up, cross-domain, collaborative approach.

Figure 1:

Mothers’ speech to infants. (A) Mothers’ word types across 5 minutes of structured play; (B) Mothers’ word types and tokens across 45 minutes of home activities; (C) Bouts of silence during everyday activities (left side) and structured tasks (right side). From Tamis‐LeMonda, C. S., Kuchirko, Y., Luo, R., Escobar, K., & Bornstein, M. H. (2017). Power in methods: Language to infants in structured and naturalistic contexts. Developmental science, 20(6), e12456.

Figure 2:

Mothers’ words to infants during everyday activities. (A) Words to infants during feeding, standardized around mothers’ use of each word category across all routines. Highlighted bars represent words with a significantly high frequency in the specific routine; (B) Words to infants during grooming (bathtime and getting dressed), standardized around mothers’ use of each word category across all routines. Highlighted bars represent words with a significantly high frequency in the specific routine Note: Not shown here is the similarly significant word specificity for activities of bookreading, toy play, and transition time. From Tamis‐LeMonda, C. S., Custode, S., Kuchirko, Y., Escobar, K., & Lo, T. (2019). Routine language: Speech directed to infants during home activities. Child Development, 90(6), 2135–2152.

Figure 3.

The location context of speech to infants. The categories of words that mothers direct to infants in different rooms during everyday activities. From Custode, S. A., & Tamis‐LeMonda, C. (2020). Cracking the code: Social and contextual cues to language input in the home environment. Infancy, 25(6), 809–826.

Figure 4:

Duration sitting independently in 5-month-old infants in six cultures (Italy, Argentina, Korea, USA, Kenya, & Cameroon). From Karasik, L. B., Tamis-LeMonda, C. S., Adolph, K. E., & Bornstein, M. H. (2015). Places and postures: A cross-cultural comparison of sitting in 5-month-olds. Journal of Cross-Cultural Psychology, 46(8), 1023–1038.

Figure 5:

Cultural context and practices in Tajikistan. (A) Dwellings and living spaces are spread out over courtyards, rather than conjoined rooms. (B) Infants are cradled in a gahvora, where their limbs are bound. Gahvora cradles differ across household socio-economic status; some gahvoras have intricately carved details, fancy bindings and coverings, and others are less elaborate. (C) Percent of infants who walk at each age, comparing Taj infants to ages on WHO norms. From Karasik, L. B., Adolph, K. E., Fernandes, S., Roboinson, S. R., & Tamis-LeMonda, C. S. (in press). Gahvora cradling in Tajikistan: Cultural practices and associations with motor development. Child Development.

Figure 6:

Object play in infants from Hispanic and non-Hispanic families. (A) Distributions of bouts of object play in the two groups of infants indicate a preponderance of brief play episodes. (B) Accumulated time manipulating objects in the two groups of infants indicate that brief bouts add up to immense amount of time with objects (i.e., ~60 of the time in both groups). From Herzberg, O., Fletcher, K. K., Schatz, J. L., Adolph, K. E., & Tamis‐LeMonda, C. S. (2022). Infant exuberant object play at home: Immense amounts of time‐distributed, variable practice. Child development, 93(1), 150–164. From Swirbul, M. S., Herzberg, O., & Tamis-LeMonda, C. S. (2022). Object play in the everyday home environment generates rich opportunities for infant learning. Infant Behavior and Development, 67, 101712.

Figure 7:

Mothers’ behaviors during bouts of infant object interactions. Each row represents an infant across two hours of natural activity at home. Colored bars are times infants interacted with objects, color-coded for whether mothers provided action and language about the referent object (dark red), only language about the referent object (pink), only touch or gesture (orange), or no input (blue). From Suarez‐Rivera, C., Schatz, J. L., Herzberg, O., & Tamis‐LeMonda, C. S. (2022). Joint engagement in the home environment is frequent, multimodal, timely, and structured. Infancy, 27(2), 232–254.

Figure 8:

Infant play type and duration in the presence of different types of mother joint engagement. (A) Infant play type (complex or simple) when mothers provide multimodal input (talk and touch/gestures geared to the object of infant touch), language input (talk about the object of infant touch), manual input (touch/gestures geared to the object of infant touch), or neither. (B) Duration of infant play bouts when mothers provide multimodal input, language input, manual input, or neither. From Schatz, J. L., Suarez‐Rivera, C., Kaplan, B. E., & Tamis‐LeMonda, C. S. (2022). Infants’ object interactions are long and complex during everyday joint engagement. Developmental science, 25(4), e13239.

Figure 9:

Associations between infant object touch, mother naming, infant word knowledge, and age of acquisition for object words. (A) Scatterplot of the number of infants who touched objects against mothers’ naming of the object; (B) Plotting the number of infants whose vocabularies contained the word for an object against mothers’ naming of the object; (C) Plot of the number of infants who manipulated an object against the age of acquisition for the object name based on language production data in Wordbank; (D) Plot of the number of mothers who named an object against the age of acquisition for the object name based on language production data in Wordbank. From Suarez‐Rivera, C., Linn, E., & Tamis‐LeMonda, C. S. (2022). From Play to Language: Infants’ Actions on Objects Cascade to Word Learning. Language Learning, 72(4), 1092–1127.

Figure 10:

Correspondence between mothers directing whole-body verbs and manual verbs to their infants and infants’ whole-body and manual actions (3 sec before and 3 sec after the verb).

Figure 11:

Early home learning environment trajectories in relation to measures in Kindergarten and 5^th grade. (A) Six trajectories of home learning environments identified in a longitudinal study of children from 1 year to 5 years of age; (B) Trajectories in relation to preschoolers’ PPVT (receptive vocabulary) scores; (C) Trajectories in relation to academic success and academic risk classifications. From Rodriguez, E., & Tamis-LeMonda, C. S. (2011). Trajectories of the Home Learning Environment across the First Five Years: Associations with Children’s Language and Literacy Skills at PreKindergarten. Child Development.Vol 82(4), pp. 1058–1075. Tamis-LeMonda, C. S., Luo, R., McFadden, K. E., Bandel, E., & Vallotton, C. (2017). The Early Home Learning Environment Predicts Children’s 5th Grade Academic Skills. Applied Developmental Science, 1–17.