Bilingual people often report that they feel different when switching from one language to another. Take Karin, a fictitious bilingual, for example. She might use German informally at home with family, in the pub, and while watching football. But she uses English for more structured, professional aspects of her life as an international lawyer.
This contextual change of language is not simply superficial, it goes hand-in-hand with a host of perceptual, cognitive and emotional trends. Research shows that language linked to experiences shapes the way we process information. So if someone was to utter the words “Ich liebe dich” to Karin, she might well blush, but by the same token, “I love you” might not alter her cheek color at all. It’s not a matter of proficiency: Karin is equally fluent in German and English, but her emotional experiences are bound more strongly to her mother tongue, simply because she experienced more fundamental, defining emotions as a child.