speech style

Japanese can be spoken in two different styles. One is the polite style, and the other is the casual. You talk casually only with your family or close friends. And since children usually learn language from their families, initially their Japanese is casual like chatting, for example, with your mom. Though my students are expected to speak to me politely, they sometimes let words slip in the casual style. When this happens, it seems to me that a cute little child has suddenly appeared, instead of a dignified adult. The contrast is quite charming, but I must correct them nonetheless.