The input's role
Although genetic factors predominantly drive brain function and organization, environmental factors are also responsible for its design. Research shows that general child development is strongly influenced by the environment in which they are immersed and by the daily input (Kuhl et al., 2001; Saffran, 2003). For example, addressing infants with specific communicative intent or using a special speech known as “Baby-Talk” from the first days of life is crucial for their subsequent development (Kuhl et al., 1997; Liu et al., 2003). It is not only the quantity of daily input to which children are exposed that determines different developmental trajectories, but also the quality of the input itself (Hirsh-Pasek et al., 2015). Therefore, studying infants’ development also means considering multiple factors and intertwining different domains (D’Souza et al., 2017).

References:
- D’Souza, D., D’Souza, H., & Karmiloff-Smith, A. (2017). Precursors to language development in typically and atypically developing infants and toddlers: the importance of embracing complexity. Journal of Child Language, 44(3), 591–627. https://doi.org/10.1017/S030500091700006X
- Kuhl, P. K., Tsao, F. M., Liu, H. M., Zhang, Y. & De Boer, B. (2001). Language/culture/mind/brain: Progress at the margins between disciplines. Annals of the New York Academy of Sciences, 935, 136–174.
- Saffran, J. R. (2003). Statistical language learning: Mechanisms and constraints. Current Directions in Psychological Science, 12 (4), 110–114.
- Hirsh-Pasek, K., Adamson, L. B., Bakeman, R., Owen, M. T., Golinkoff, R. M., Pace, A., Yust, P. K. S., & Suma, K. (2015). The Contribution of Early Communication Quality to Low-Income Children’s Language Success. Psychological Science, 26(7), 1071–1083. https://doi.org/10.1177/0956797615581493
- Kuhl, P. K., Andruski, J. E., Chistovich, I. A., Chistovich, L. A., Kozhevnikova, E. V., Ryskina, V. L., Stolyarova, E. I., Sundberg, U. & Lacerda, F. (1997). Cross-language analysis of phonetic units in language addressed to infants. Science, 277, 684–686.
- Liu, H. M., Kuhl, P. K. & Tsao, F. M. (2003). An association between mothers’ speech clarity and infants’ speech discrimination skills. Developmental Science, 6, F1–F10.