A language habit observed in Norway and Ireland. Where an American would say "uhm" while you were talking to encourage you to go on, the aspirated affirmative is the word "yes", but said while drawing in breath. Unfortunately, this is similar to the American signal that the listener wants to interrupt, resulting in some pretty amusing conversations (to watch).

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Actually, from personal experience as an American in Scandinavia, it was even more jarring.  When someone quickly takes in their breath, with their mouth shaped roughly like an "O", it signals that the person has been startled by something, like something about to fall or break.  For a few times until I got used to it, I kept jumping at the sound, looking around to see where the emergency was!