A chivalrous battle of languages: when speaking with someone whose mother tongue is a language I speak as a second language, I notice that there is a tendency for both of us to prefer the language of the other. Why is this? Two hypotheses. One: out of deference or politeness we both want to ease the flow of conversation by accommodating the linguistic preferences of the other. Two: we each prefer speaking a foreign language, and want to exploit the opportunity to do so on neutral terrain.