“…Because of the centrality of functional structure in modern generative grammar, the analysis of functional categories was similarly of central importance in our study, as it has been for numerous other researchers in normal (Hyams, 1996;Radford, 1995;Sinka & Schelletter, 1998;Wexler, 1998) and impaired (e.g., Jakubowicz, Durand, Rigaut, & van der Velde, 2001; Leonard, 1998) language development. For this reason, our coding system was developed with a focus on the analysis of these items.…”