Quantifying the perceptual value of lexical and non-lexical channels in speech
This work addresses a fundamental problem in speech communication research by providing a generalised paradigm to study non-lexical information across unconstrained lexical content, though it is incremental in advancing existing methods.
The paper tackles the challenge of quantifying the relative effects of lexical and non-lexical channels in speech on listener expectations, showing that non-lexical information yields higher consensus among participants even when it leads to poorer discriminative turn judgements than lexical content alone.
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.