(By Jakob Lesage): "This feature asks whether intransitive verbs can take a phonologically bound morpheme that signals the addition of just one role in the event denoted by the verb. This could be a causative affix or clitic, an applicative marker (benefactive, instrumental, etc.), etc. The marker has to be productive. Note that there is no logical dependency with GB155 on causative markers, as a language could have causatives that change a verb's valency from 2 to 3 but not from 1 to 2.