A learner nativises the target language in early stages of second language acquisition by interpreting language input and producing output with reference to an internal (i.e., first language) norm. Denativisation occurs at later stages of acquisition, when the learner changes to an external (i.e., target language) norm.
Andersen's Nativisation Model developed in the late 1970s built on Schumann's pidginisation or acculturation model which relates second language progress to social and cultural distance: learners who feel distant from the target language culture will reject its linguistic norms via nativisation, while those who feel closer will adopt the new norms through denativisation.
This process bears comparison with Piaget's notion of adaptation, with its two components of assimilation (adaption of the environment to the learner) and accommodation (adaption of the learner to the environment).
Classroom illustration: Story adaptation