This article discusses how language change and diffusion in Tarifit (Rif-Berber, North Morocco) can be explained by system-internal factors. The examined cases examined concern several innovation processes triggered by the vocalisation phe-nomenon of the liquids /r/ and /ṛ/ and involving both phonological and morpho-logical features and structures. The analyses presented analyses confirm that innovation can also be formally motivated, which refutes Croft's (2000: 38) claim that only functional factors can induce language change. Moreover, they show how functional properties may determine the success of the diffusion of variants. As such, they offer evidence against the claim that only social factors are accountable for variant selection (Milroy 1992: 201‒202; Croft 2000: 38, 54). The considered data considered in this contribution come from the Atlas Linguistique des variétés berbères du Rif (Lafkioui 2007), a geolinguistic study of the Berber varieties of North Morocco.