The discourse conditions for the use of the complementizer that in conversational English

The complementizer that in English, as in I heard (that) you were sick, has widely been regarded as optional. Our research demonstrates that the use of that in such utterances in conversation is highly related to various other features in the discourse. First and second person subjects, the verbs think and guess, and auxiliaries, indirect objects, and adverbs in the main clause, and pronominal complement subjects are all significant in predicting the use of that. As seemingly disparate as these factors are, their influence finds a unified explanation in the acknowledgement that certain combinations of main clause subjects and verbs in English (such as I think) are being reanalyzed as unitary epistemic phrases. As this happens, the distinction between ‘main’ and ‘complement’ clauses is being eroded, with the omission of that a strong concomitant. Our findings show that the factors most likely to contribute to this reanalysis are precisely those which relate either to the epistemicity of the main subject and verb or to the topicality of the complement at the expense of the main clause.