What is the effect of motherese on development? Most cultures (Falk, 2009) have a special type of language that is used to talk to children: infant-directed-speech (IDL; or informally, motherese, baby talk). For instance, Fernald (1992) argues that motherese is an evolved phenomena that was selected for. This suggests that it has a benefit to child development, hence my questions:

What benefit does IDL provide children?
How do the features of IDL benefit the cognitive development of children?
Are there benefits beyound effects on language-acquisition?

Notes

The only benefit I am familiar with (shameless self plug) is in helping avoid reversal-errors in pronoun acquisition but Kaznatcheev (2010) is only a theoretical prediction based on a particular computational model of questionable (1, 2) empirical validity.

I am interested in the developmental benefit of the very specific language used in IDL, not about the benefit of maternal care in general.


References
Fernald, A. (1992). &quot;Human maternal vocalizations to infants as biologically relevant signals: An evolutionary perspective.&quot; In J. H. Barkow, L. Cosmides, &amp; J. Tooby (Eds.) The adapted mind: Evolutionary psychology and the generation of culture (pp. 391-428).
Falk, D. (2009). Finding our tongues: Mothers, infants and the origins of language. New
York: Basic Books.
Kaznatcheev, A. (2010). &quot;A Connectionist Study on the Interplay of Nouns and Pronouns in Personal Pronoun Acquisition.&quot; Cognitive Computation 2(4): 280-284.
Motherese may play a role in emotional development. 

Soken and Pick write: "Concurrent with the exaggerated speech of motherese, there are probably exaggerated facial displays, allowing infants to explore the particular aspects of the face... Child-centered displays may serve as opportunities for learning about affective events."

Walker-Andrews (1997) also suggests that "the presence of the face acts as a setting for attending to the affective quality of the voice."

Yet, according to a recent, extensive review on motherese (Saint-Georges et al., 2013), its role in emotion and cognition  is still an open area of research.

References


N. H. Soken and A. D. Pick, “Intermodal Perception of Happy and Angry Expressive Behaviors by Seven‐Month‐Old Infants,” Child development, vol. 63, no. 4, pp. 787–795, 1992.
A. S. Walker-Andrews, “Infants' perception of expressive behaviors: differentiation of multimodal information.,” Psychological Bulletin, vol. 121, no. 3, p. 437, 1997.
C. Saint-Georges, M. Chetouani, R. Cassel, F. Apicella, A. Mahdhaoui, F. Muratori, M. C. Laznik, and D. Cohen, “Motherese in Interaction: At the Cross-Road of Emotion and Cognition? (A Systematic Review),” PLoS ONE, vol. 8, no. 10, p. e78103, Oct. 2013.