Quantifying the perceptual value of lexical and non-lexical channels in
  speech
Sarenne Wallbridge Peter Bell Catherine Lai
Speech is a fundamental means of communication that can be seen to provide
two channels for transmitting information: the lexical channel of which words
are said, and the non-lexical channel of how they are spoken. Both channels
shape listener expectations of upcoming communication; however, directly
quantifying their relative effect on expectations is challenging. Previous
attempts require spoken variations of lexically-equivalent dialogue turns or
conspicuous acoustic manipulations. This paper introduces a generalised
paradigm to study the value of non-lexical information in dialogue across
unconstrained lexical content. By quantifying the perceptual value of the
non-lexical channel with both accuracy and entropy reduction, we show that
non-lexical information produces a consistent effect on expectations of
upcoming dialogue: even when it leads to poorer discriminative turn judgements
than lexical content alone, it yields higher consensus among participants.