Research on the acquisition of two first languages from birth (2L1A) has focused, among other issues, on how the grammars of the two languages being acquired interact (e.g. Bhatia & Ritchie, 2012 ; De Houwer, 2009 ; Deuchar & Quay, 2000 ; Döpke, 2000 ; Köppe & Meisel, 1995 ). A case in point is natural interpreting which evidences how bilingual children exposed to two languages from birth deal with the grammatical properties of the two languages and how this leads them to potentially convey the same message in either (or both) of these languages. More specifically, as part of the simultaneous processing of their two L1s, 2L1 bilingual children have been reported to often translate between their two L1s ( Álvarez de la Fuente & Fernández Fuertes, 2012 , 2015 ; Cossato, 2008 ; Harris, 1980a , 1980b ; Harris & Sherwood, 1978 ), a phenomenon that has been called natural interpreting ( Harris, 1977 , 2003). In this respect, natural interpreting can be included with other language contact phenomena, such as interlinguistic influence or code-switching, as a typical defining property of 2L1A. Therefore, in this study we aim to offer an analysis of the way in which Spanish-English bilingual children use natural interpreting in their 2L1A process by focusing on the Spanish-English bilingual corpora freely available through the CHILDES project ( MacWhinney, 2000 ).
