Sentence-initial I think (that) and I believe (that): Prosodic evidence for uses as main clause, comment clause and discourse marker

Sentence-initial pronoun-verb combinations such as I think, I believe are ambiguous between main clause use on the one hand and adverbial or discourse use on the other hand. We approach the topic from a prosodic perspective. Based on corpus data from spoken British English the prosodic patterns of sentence-initial I think and I believe are analysed and related to their interpretation in context. We show that these expressions may function as main clause (MC), comment clause (CC) or discourse markers (DM) and that the speaker’s choice is reflected in the prosody. The key feature is prosodic prominence: MCs are reflected by accent placement on the pronoun, CCs by an accent on the verb, while DMs are unstressed.