On noncausal/causal alternations in Tima (Nuba Mountains, Sudan)

Tima, a language spoken in the Nuba Mountains of Sudan, uses three derivation markers (with various allomorphs) to either increase or decrease the valency of the verb. Middle voice and antipassive marking are used to reduce the valency. Causative marking may on the one hand increase the valency of monovalent verbs, while on the other hand it functions as an anticausative/passive marker for erstwhile transitive verbs. The distribution of these derivation markers across the formal alternation patterns augmentation, reduction, and double marking (as described by Nichols et al. 2004), is investigated in order to establish certain verb groups. Due to the peculiar behaviour of the causative marker, in that the device can be used to form a causal verb as well as a noncausal verb, the connection between causative and passive functions is further scrutinised by relating the Tima data to a grammaticalisation path, as suggested by Haspelmath (1990), from causative via reflexive-causative to passive. Tima deviates from this path: A reflexive-causative function is not attested; instead we find an anticausative function. The unlikely assumption that the Tima ergative construction originates from a further grammaticalisation of the causative-passive morpheme is also considered.