137 REFLECTION ON THE AGREEMENT AND TENSE OMISSION MODEL OF SPECIFIC LANGUAGE IMPAIRMENT: A CORPUS-BASED STUDY * YI-AN LIN Abstract On the basis of the Leonard corpus in the Child Language Data Exchange System, the present paper tries to evaluate Wexler, Schütze & Rice’s (1998) two-factor account of specific language impairment (SLI), the Agreement and Tense Omission Model (ATOM), and to figure out the nature of syntactic errors made by SLI children. The result shows that the SLI children in the Leonard corpus did experience difficulties in the use of the third-person, singular, present tense –s and the preterite verb forms as predicted by ATOM. However, it is found that these SLI children mark tense better than agreement. ATOM cannot explain such a discrepancy. In addition, it is shown that case marking is unimpaired in these children’s grammars. Therefore, an alternative account which claims that nominative case is assigned by an interpretable mood feature on T is adopted in order to account for the findings here. Moreover, it is found that these SLI children do not have any problem with A-movement. This suggests that their agreement marking errors are not due to the underspecification of the agreement feature on T as proposed by ATOM. They may instead be merely spellout errors. By contrast, it was shown that these SLI children’s problems with auxiliary inversion may be due to the underspecification of the tense feature. Hence, this indicates that their tense marking errors are caused by the underspecification of the tense feature on T. However, the proposal that the interpretable tense feature may sometimes be underspecified requires the functional head T to have another interpretable feature: mood. Such an amendment prevents the derivation of sentences from crashing at semantic interface. In summary, the primary deficit in SLI children is shown to be the specification of the tense feature, and this is arguably due to the fact that tense is a conceptually complex notion. 1. Introduction Specific Language Impairment (SLI), also known as developmental dysphasia, refers to a delayed or deviant language development of children in the absence of neurological trauma, cognitive impairment, psycho-emotional disturbance, or motor-articulatory disorders (Eisenbeiss, Bartke, & Clahsen 2005). Due to the fact that SLI is a heterogeneous disorder, the identification of SLI is usually based on a set of exclusionary criteria. As Leonard (1998) mentioned, there are some primary criteria for the diagnosis of SLI. Namely, language test scores are of -1.25 standard * This paper is based on the third chapter of my 2005 master’s dissertation submitted to University of Essex. Therefore, I am grateful to my supervisor, Prof. Andrew Radford, for his guidance on the analysis presented here. I also thank the audience at the 1 st Newcastle Postgraduate Conference in Theoretical and Applied Linguistics and the anonymous reviewer for the valuable comments and suggestions. All the remaining errors are my own responsibility.