|Abstract:||This paper examines the emergence of UG patterns appearing in the phonological analysis of Japanese adaptations of French words. The results provide us with evidence for adulthood access to UG. The issue of the emergence of UG outside of first language acquisition has arisen in several other areas of linguistic study: Acquisition of second language (Flynn and O'Neil eds. 1988, Epstein, Flynn and Martohardjono 1996), Interlanguage phenomena (Browslow and Park 1995), Creolization (De Graff 1999). Our study contributes to 1) the linguistic theory of acquisition and 2) the relevance of the Optimality model (Prince and Smolensky 1993) to the study of acquisition. In the linguistic theory of acquisition, one of the controversial issues is whether the ON/OFF parameters are fixed in the early stage of language acquisition; or on the contrary whether UG latent in L1 is accessible in a later stage of life. Phonological analysis of adapted forms of foreign input shows that structures (and the grammatical principles that underlie them) that are not overt in the L1 lexicon may emerge in the adaptation process and these structures seem to be the unmarked ones cross-linguistically, indicating that they belong to UG. We conclude that UG can play a role in adulthood acquisition and hence that it is accessible later stages in life.