Complex verbs in Nupe and Yoruba

This paper examines the structural behaviour of various types of complex verbs in Nupe and Yoruba in relation to causative constructions. When such verbs occur in simplex non-agentive causative sentences as well as in agentive non-causative sentences, they freely permit sentence embedding, resulting in biclausal causative structures. But in the case of non-agentive causatives, it is only Yoruba which allows the verbs to be irregularly embedded into causative matrix sentences in such a way that the biclausal causative structure constitutes input to Causative Clause Union, which compresses it into a uniclausal agentive causative sentence. Functionally, Yoruba uniclausal and biclausal agentive causatives are intercharigeable in many cases. On the other hand, only uniclausal agentive causatives are attested in Nupe, as Causative Clause Union has disappeared from its grammar. It is concluded that causative constructions in these languages demonstrate clearly that the CCU rule is motivated by a diachronic process of moving from a pragmatic mode of expression to a syntacticized one, and where a particular target has been hit, the rule ceases to function.