The Representation and Processing of Tense, Aspect & Voice across Verbal Elements in English

The Representation and Processing of Tense, Aspect & Voice across Verbal Elements in English Jerry T. Ball (Jerry.Ball@wpafb.af.mil) 711 th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45431 Abstract We consider the representation and processing of the English verb features tense, aspect and voice, within a computational cognitive model of human language processing. We assume that a collection of features is associated with each verbal element and that these features may project to the clauses in which they occur. When multiple verbal elements occur, it is possible for the features to conflict, necessitating mechanisms of feature blocking and overriding to determine feature projection. The alternative of having multiple entries in the mental lexicon for each verbal element with different feature sets is avoided due to the ambiguity that would be introduced, and the weak grammatical motivation for doing so. However, we do assume an ambiguity in the case of most v-ed and v- base verb forms, with the past tense v-ed form being distinct from the past participle v-ed form and the present tense v-base form being distinct from the non-finite v-base form. We assume that every finite clause expresses a tense and voice feature and many finite clauses express an aspect feature as well. We consider the case of transitive and intransitive verbs in combination with the auxiliary verbs ―be‖ and ―have‖ in finite clauses. For intransitive verbs, we introduce an active/inactive voice feature distinction which aligns with the transitive distinction between active and passive voice. Keywords: grammatical feature, tense, aspect, voice Introduction We consider the representation and processing of the English verb features tense, aspect and voice, within the context of a pseudo-deterministic model of human language processing (Ball, 2011a) implemented in the ACT-R cognitive architecture (Anderson, 2007). The pseudo- deterministic model reflects the integration of a highly parallel, probabilistic, and context dependent, activation and selection mechanism and non-monotonic context accommodation mechanism (with limited parallelism) with what is otherwise an incremental processor which pursues the best analysis. The overall effect is a human language processor (HLP) which presents the appearance and efficiency of deterministic processing, despite the rampant ambiguity which makes truly deterministic processing impossible. Our non-monotonic context accommodation mechanism replaces the monotonic look-ahead mechanism of Marcus’s deterministic parser (Marcus, 1980) and is argued to be more cognitively plausible (Ball, 2011a). We assume that a collection of verb features is associated with each verbal element (cf. Gazdar et al., 1985) and that these features may project to the clauses in which they occur. We consider the composition of verb features across verbal elements within a clause. When multiple verbal elements occur, it is possible for the verb features to conflict. The context accommodation mechanism, which has been independently motivated (Ball, 2010a), is crucial for handling conflicts. In particular, we propose specialized mechanisms of feature blocking (i.e. a feature of a preceding verbal element precludes projection of a conflicting feature of a subsequent verbal element) and feature overriding (i.e. a feature of a subsequent verbal element overrides a conflicting feature of a preceding verbal element) to handle conflicts. Feature overriding is non-monotonic in that it changes the incrementally evolving representation. Our non-monotonic approach can be contrasted with approaches which rely on monotonic unification of non- conflicting features (Gazdar et al., 1985; Sag et al., 1986; Sag, Wasow & Bender, 2003). To avoid feature conflicts, such approaches tend to posit alternative entries in the mental lexicon which are structurally ambiguous, often linguistically unmotivated and sometimes grammatically inadequate. For example, ―a few books‖ is grammatical in English despite the fact that ―a‖ is singular and ―few‖ and ―books‖ are plural. In a monotonic unification-based approach, the number feature of ―a‖ must somehow unify with the number feature of ―few‖ and ―books‖. To handle this, one could posit a plural or number lacking version of ―a‖. But this introduces ambiguity and lacks linguistic motivation. In our non-monotonic approach, the plural feature of ―few‖ and ―books‖ is allowed to override the singular feature of ―a‖ (Ball, 2010b). Feature blocking and overriding are concerned with the composition of features across lexical items within constructions and differ from non-monotonic default constraint inheritance (cf. Sag, Wasow & Bender, 2003, 229ff.) which is concerned with defeasible inheritance of features within individual lexical items—which we also use (Ball, 2011b). English has a highly restricted number of distinct verb forms which include the following: V–base (or V–plain) form (e.g. ―give‖, ―go‖) V–s form (e.g. ―gives‖, ―goes‖) V–ed form (e.g. ―gave‖, ―went‖, ―kicked‖) V–en form (e.g. ―given‖, ―gone‖) V–ing form (e.g. ―giving‖, ―going‖)