ABSTRACT
Longitudinal study has long been considered essential for substantive work on the acquisition of a first language (L1). Leopold’s (1939) decade-long study of the acquisition of English and German by his daughter is among the best known early examples for this approach. Some 30 years later, Brown (1973) completed sophisticated longitudinal studies that addressed various ages of L1 learners. Miller (1979) used dense time intervals as well as a broad variety of informal contexts in parentchild interaction to expand our understanding of the gradual development of a first language; and in the 1980s, a crosslinguistic dimension was added to the longitudinal study of L1 development under Slobin’s direction (Slobin, 1985).
