Patientive (S = O) ambitransitives are those where the single argument of the intransitive (S) corresponds to the object (O) of the transitive. For example, in the sentence "John (S) tripped" and "John (A) tripped Mary (O)", John is doing the falling in the first sentence. Likely candidates for this type of ambitransitive are verbs that affect an agent spontaneously, or those that can be engineered by an agent. English has "bend", "break", "burn", "burst", "change", "cool", "enter", "extend", "fall", "frighten", "grow", "hurry", "melt", "move", "open", "spill", "stretch", "trip", "turn", "twist", "walk", and many other verbs. Such verbs are also called labile verbs (or "ergative verbs").