According to Cruz, it is not possible for the same verb to function either as transitive or as intransitive. The identification of morphemes as valency-change operators takes only syntactic criteria into consideration. However, from a semantic point of view, Cruz notes that these morphemes are somewhat restricted in the type of thematic role that the inserted (or demoted) argument can receive. Cause-derived verbs select a subject that receives the thematic role CAUSER. On the other hand, verbs derived by the 'reflexive / reciprocal' morpheme select a single argument, characterized at the same time as AGENT and PATIENT.