This paper argues that wieder (‘again’) can be used in wh-questions as a modal particle. This use derives from the use of wieder as a temporal adverb, due to grammaticalization, in accordance with Traugott's hypothesis of a semantic-pragmatic tendency for meanings to become increasingly situated in the speaker's belief-state or attitude toward the situation. By using wieder as a modal particle, the speaker can indicate that s/he knew the answer to the question previously but is at present not aware of it.
It is shown that several other temporal adverbs, such as noch (‘still’) and gleich (‘soon’), may serve as modal particles in questions, with a function very similar to that of wieder. This is due to semantic bleaching, a concomitant of grammaticalization, which neutralizes the differences in lexical semantics between these elements. These modal particles indicate that the answer to the question is part of the speaker and recipient's common ground, but not activated at the moment in the speaker's and/or the hearer's consciousness.