Many multilinguals report different personalities, or even different worldviews, when they speak their different languages.
It’s an exciting notion, the idea that one’s very self could be broadened by the mastery of two or more languages. In obvious ways (exposure to new friends, literature and so forth) the self really is broadened. Yet it is different to claim—as many people do—to have a different personality when using a different language. A former Economist colleague, for example, reported being ruder in Hebrew than in English. So what is going on here?
Benjamin Lee Whorf, an American linguist who died in 1941, held that each language encodes a worldview that significantly influences its speakers.
Johnson: Do different languages confer different personalities?
Mind Hacks points out:
... bilingual speakers may have different associations with each language – for example, home and work – and so come to associate different sorts of social behaviours with each.
With every language, a personality?
I'm personally inclined rather strongly to agree with the Whorfian view.