Fagan MK. Mean length of utterance before words and grammar: longitudinal trends and developmental implications of infant vocalizationsJ Child Lang. 2009; 36(3): 495-527.
In this study, researchers measured developmental changes in various types of infant utterances, and found that changes occur in predictable ways with regards to both age and language milestones. Results led to new perspectives on the processes underlying the transition from babbling to first words.

Iverson JM. Developing language in a developing body: the relationship between motor development and language development. J Child Lang. 2010; 37(2): 229-261. 
This review article contends that motor acquisitions provide infants with an opportunity to practice skills relevant for communication development and language acquisition before they are needed for that purpose.

Kuhl, Patricia. Early language acquisition: cracking the speech code. Nat Rev Neurosci. 2004; 5(11): 831-843.
Early language acquisition is constrained at the perceptual, computational, social, and neural levels. The author concludes that identifying the constraints and determining whether those constraints reflect innate language-specific or general knowledge will be the focus of future research on language learning.

Lyytinen, P., Laakso, M.-L., Poikkeus, A.-M. and Rita, N. The development and predictive relations of play and language across the second year. Scand J Psychol. 2008; 40(3): 177–186.
Results from this study show that vocabulary production and symbolic play at 14 months and language outcomes at 18 months are predictive of language and cognitive skills at 2 years.

Mayberry R, Nicoladis E. Gesture reflects language development: evidence from bilingual children. Psychol Sci. 2000; 9(6): 192-196.
This study explored the relationship between gesture and language development in French-English bilingual children from 2 to 3.5 years old. Researchers found that the onset of iconic and beat gestures coincided with the onset of sentence-like utterances separately in each of the children’s two languages, supporting the idea that gesturing is not independent from language development.

Nip IS, Green JR, Marx DB. Early speech motor development: cognitive and linguistic considerations. J Commun Disord. 2009; 42(4): 286-98.
The goal of this study was to examine the developmental trajectories of various orofacial movements during the early stages of language acquisition. Silent spontaneous movements were consistently slower than those for babble and words, suggesting that linguistic and cognitive processing demands affect speech-related movements.

Nip IS, Green JR, Marx DB. The co-emergence of cognition, language, and speech motor control in early development. J Commun Disord. 2011; 44(2): 149-60.
This article presents preliminary evidence of the interaction between cognition, language, and speech motor skills during early development. Further work is needed to identify and quantify causal relationships among co-emerging skills in these domains.

Stark RE, Rose SN, McLiagan M. Features of infant sounds: the first eight weeks of life. J Child Lang. 1975; 2: 205–221.
In this study, researchers recorded the vocalizations of two girls between one and eight weeks of age, and found particular features that appeared to be highly typical of cry and discomfort sounds, and others typical of vegetative sounds.

Tsao FM, Liu HM, Kuhl PK. Speech perception in infancy predicts language development in the second year of life: longitudinal study. Child Dev. 2004; 75(4): 1067-1084.
Results from this study demonstrate that speech perception performance at 6 months predicts receptive and expressive language skills at 2 years, supporting the idea that phonetic perception may play a key role in language acquisition.

Wetherby AM, Rodrigues GP. Measurement of communicative intentions in normally developing children during structured and unstructured contexts. J Speech Lang Hear Res. 1992; 35(1): 130-139.
The purpose of this study was to examine the effect of sampling context on measurements of expressive language by typically-developing children during various stages of linguistic development. Authors found that the production of requests and comments increased significantly from the prelinguistic stage to the multiword stage in both structured and unstructured contexts. Furthermore, significantly more requests were produced during the structured context.