This paper reports the results of a spontaneous-speech study on Case-checking in early Russian. While singular Case endings are adultlike and abundant before age 2, correct plural non-NOM forms are rare. Inspired by Hoekstra and Hyams (1995), we argue that this is due to the underspecification of the Number head.

We investigated structural, inherent, and lexical Case in the spontaneous speech of three monolingual Russian-acquiring children between the ages of 1;8-2;0, and found 89% correct Case assignment in the singular, while in plural only 12% of non-NOM Cases were assigned correctly.

Close examination of the children’s plural forms suggests that plural is not productive. On this basis, we propose that the nominal Num head is initially underspecified, namely, it represents [-plural] only (cf. Müller, 1994). In case of a plural N, an underspecified Num head breaks the Case-chain and blocks Case feature checking, yielding default NOM forms in early Russian.