The analysis of language interactions between children in Dakar and Ziguinchor (Senegal) sheds light on the different sorts of mixed uses of language, depending on the place (the capital in the center, a regional city on the periphery) and the discursive genres (group discussions, conversations between two persons, or games with several players). Language-switching reinforces the perlucotor value of the argumentations exchanged during discussions.   In Dakar, the emergence of a mixture of Wolof and French was observed whereas, in Ziguinchor, the mixing of languages was a sign of the user's plural identifications and of the maintenance of an ethnic identity.   Mixed speech is characterized by mainly extraphrastic alternations and by borrowings in the base language, which itself may also alternate between the language of one's group or wolof.