Like I think in English, (eu) acho
que in Brazilian Portuguese can function as a discourse marker (DM)
with more than one meaning, and these meanings are curiously diametrically
opposed. Certainty, doubt or uncertainty is inferred by hearers in an
interactional context. In a sample of audio-video recorded interviews, the
occurrences of this DM were classified by meaning, and association tests between
meanings and linguistic factors (pronoun realization, polarity, position in
utterance), real-world features (type of evidence from which the speaker says
something, and discursive topic), prosody (F0, intensity and duration), and
facial expressions were carried out. Differences that distinguish these factors
were identified among certainty, doubt and uncertainty uses. The certainty
meaning of (eu) acho que was associated with pronoun presence, more
formality and topics in which the speaker had direct evidence. Uncertainty and
doubt were associated with pronoun absence, less formality and topics in which
the speaker did not have direct evidence. Patterns of intensity and duration
acted to distinguish the certainty, doubt and uncertainty meanings of (eu)
acho que. In a conditional decision tree, the position in utterance,
presence of a pronoun, type of speaker’s evidence, discursive topic, and
duration helped to disambiguate the meanings of (eu) acho que.
These results suggest the relevance of a multilevel approach to describe DM, in
different languages, at least with respect to mental state verbs.