De Ruiter, J. P., Mitterer, H., & Enfield, N. J. (2006). Projecting the end of a speaker's turn: A cognitive cornerstone of conversation. Language,82(3), 515-535.
A key mechanism in the organization of turns at talk in conversation is the ability to anticipate
or PROJECT the moment of completion of a current speaker’s turn. Some authors suggest that this
is achieved via lexicosyntactic cues, while others argue that projection is based on intonational
contours. We tested these hypotheses in an on-line experiment, manipulating the presence of
symbolic (lexicosyntactic) content and intonational contour of utterances recorded in natural conversations.
When hearing the original recordings, subjects can anticipate turn endings with the
same degree of accuracy attested in real conversation. With intonational contour entirely removed
(leaving intact words and syntax, with a completely flat pitch), there is no change in subjects’
accuracy of end-of-turn projection. But in the opposite case (with original intonational contour
intact, but with no recognizable words), subjects’ performance deteriorates significantly. These
results establish that the symbolic (i.e. lexicosyntactic) content of an utterance is necessary (and
possibly sufficient) for projecting the moment of its completion, and thus for regulating conversational
turn-taking. By contrast, and perhaps surprisingly, intonational contour is neither necessary
nor sufficient for end-of-turn projection.