Speech Melody Controls Alternation Of Speakers

In a normal conversation between two people, the speakers take over from one another very rapidly. The question is how each lets the other know when he or she can start speaking. It is usually the sentence structure which provides the most important information, whilst melodic cues only play an auxiliary role.

The melodic cue that Dr Caspers has identified is an exception to this general principle. There are moments in a conversation when one of the speakers has reached the end of a complete sentence and wishes to pause for a few tenths of a second without the other person taking over the conversation. At such moments, the speaker can make use of melodic cues to indicate that he wishes to continue. To signal this intention, the speaker raises the pitch on the final stressed syllable and maintains this pitch until the subsequent pause. Dr Caspers discovered that the same melodic form has a similar function in English.

In the study at Leiden University, test subjects were played short recorded fragments of conversation. The conversations were electronically truncated at points when the speakers changed or when one of them paused briefly. At the end of each fragment, subjects indicated whether they expected the speaker to continue speaking or the other person to take over. The subject could also indicate whether the other speaker would merely produce an affirmative sound (such as ‘hmmm’ or ‘yes’), prompting the original speaker to keep talking.

In grammatically incomplete sentence fragments, it was the sentence structure that played the overriding role. No matter what melodic configuration the speaker used, hardly any of the subjects expected the other speaker to take over after the short pause. In grammatically complete fragments, however, speech melody played a much greater role. Here the rise in pitch signalling the speaker’s intention to continue speaking had a strong effect. When such a rise in pitch occurred, as many as 91% of the test subjects thought that the speaker would continue speaking, possibly after the other person made a short affirmative sound. In the absence of such a rise in pitch, only 34% to 54% thought so.