  People convey information extremely effectively through spoken interaction
using multiple channels of information transmission: the lexical channel of
what is said, and the non-lexical channel of how it is said. We propose
studying human perception of spoken communication as a means to better
understand how information is encoded across these channels, focusing on the
question 'What characteristics of communicative context affect listener's
expectations of speech?'. To investigate this, we present a novel behavioural
task testing whether listeners can discriminate between the true utterance in a
dialogue and utterances sampled from other contexts with the same lexical
content. We characterize how perception - and subsequent discriminative
capability - is affected by different degrees of additional contextual
information across both the lexical and non-lexical channel of speech. Results
demonstrate that people can effectively discriminate between different prosodic
realisations, that non-lexical context is informative, and that this channel
provides more salient information than the lexical channel, highlighting the
importance of the non-lexical channel in spoken interaction.
