I live in Belgium I don't actually know in what language I think, but it probably depends on the situation I'm in, so I guess I think in the language I need at that moment. I'm not that into languages, I'm a science-guy, but I think English is my favorite, just because almost everyone on the planet will understand you in English. But Dutch (Flemish actually) does have some nice expressions you just don't find in other languages, so I guess I like that as well