Ingestive Verbs, Causatives, and Object Symmetry in Lubukusu

The question of object symmetry compares the grammatical function of two objects in a ditransitive predicate. Of particular interest has been derived ditransitives where a valencychanging morpheme increases the valency of a transitive verb. The central question is whether an object licensed by the base verb and an object licensed by e.g. an applicative morpheme have the same grammatical function. Several aspects of grammar have been proposed to account for object (a)symmetries, such as syntactic differences, especially the height of argument licensing heads (Baker 1988, Ngonyani 1996, McGinnis 2001, Harley 2002, McGinnis & Gerdts 2003, Jeong 2007), differences in thematic role (Bresnan & Moshi 1990, Alsina & Mchombo 1993), and the animacy and person features of the two objects (Morolong & Hyman 1972, Aranovich 2009, Baker et al. 2012). In this paper, I make the novel claim that verb meaning is an additional component in determining symmetry.1 I present a case study from Lubukusu (Bantu; Kenya) where the general pattern with morphological causatives is asymmetry, but caused ingestive verbs are symmetrical. I sketch a brief analysis of these facts by building on the observation that ingestive verbs in many languages behave distinctly under causativization (Masica 1976, Amberber 2002, Næss 2007, 2009, Krejci 2012). I propose that the symmetry of caused ingestives in Lubukusu follows from a principled difference in the lexical semantics of these verbs; adopting an approach from Krejci (2012), I analyze ingestive verbs as inherent reflexive events wherein an agent causes himor herself to digest something. With caused ingestives, there is a delinking of the reflexive relationship between the causer and the ingester, and thus caused ingestives already have a causal relationship in their event structure. This contrasts with other verbs for which causativization adds a wholesale new causal subevent. It is this difference in the lexical semantic nature of the verb that provides a starting point