Although people do not usually talk at the same time, simultaneous speech by two or more speakers is frequent. In meetings, it has been calculated at around 10% of total speaking time. If, rather than total speaking time, we consider the number of speaker turns that are overlapped, the proportion of overlapping talk is much higher – up to 50% in conversation.

Given that conversations are generally perceived to proceed smoothly, the high occurrence of overlap requires explanation. However, phonetic science has largely neglected overlapping talk, and its potential theoretical importance for our understanding of linguistic structure and function have hardly been explored. An understanding of overlapping talk is also important for a number of practical applications, including those in which human-computer interaction is achieved through a speech interface.

Conversations normally conform to a turn-taking model, in which participants wait for others to stop talking before talking themselves. However, overlapping speech can be used by conversational participants to compete for the turn – in other words, overlaps are initiated in order demonstrate that the overlapper is interested in taking over the turn immediately, not when the current speaker has finished. Conversations also contain a large number of non-competitive overlaps that have different conversational functions. A common example is so-called backchannel continuers such as “uh-huh” that confirm the current talker’s right to the turn. Given that both competitive and non-competitive overlaps are well attested in conversation, the question arises as to what linguistic resources are employed by participants in order to display an overlap as turn competitive or as non-competitive.

In answering this question, previous research has focused almost exclusively on the English language. Little is known about the similarities and differences between languages, with respect to overlapping talk, particularly in regard to its phonetic aspects. Also, previous work in the field has mainly used careful impressionistic listening rather than quantitative techniques. Our project addresses the limitations of previous work by conducting a cross-linguistic study of overlapping talk, combining quantitative with qualitative methods.