The verbs ser and estar have been a subject of great debate in the literature, mainly because the adjectives that are combined with each copula are not in complementary distribution. A cognitive linguistics approach proposes that estar allows for a comparison of the entity referred to by the utterance’s subject and that very same entity that goes through a temporal change; on the other hand, ser allows for a comparison among entities of different type (Delbecque, 1997). I provide an analysis of spontaneous child-directed speech from a longitudinal database and find variation sets that may allow children to detect the differences between ser and estar. In child-directed speech, the entities referred to by the subject of a sentence with estar are always entities that undergo a perceptible change within an activity of daily life, while the entities referred to with ser never undergo a change.
