There have been many researches on the subject of oral output in linguistics both home and abroad. Previous literature focuses on pauses in oral tasks includes theoretical studies and empirical ones. This literature review consists of three parts: influential definitions of oral fluency, the definition and classification of pauses and focuses of empirical studies on pauses.

1. Theoretical studies on pauses

1.1 Definitions of L1 and L2 oral fluency

On the issue of defining ”fluency”, there are much controversy and confusion both in L1 fluency and L2 fluency. In the field of L1 fluency studies, one of the most representative opinion is the four basic characteristics of L1 oral fluency identified by Fillmore in 1979, namely, ”the ability to talk at length with few pauses, the ability to fill time with talk”, ”the ability to talk in coherent, reasoned, and ”semantically dense#8217; sentences”, ”the ability to have appropriate things to say in a wide range of contexts” and ”the ability to be creative and imaginative in their language use”. Although these are discussions applied to L1 oral fluency, they are also helpful for us to understand L2 oral fluency.

Compared with L1 oral fluency studies, more efforts were made towards L2 oral fluency. Zhang Wenzhong (1999) explains that it is because normal people have no difficulty acquiring their first language. For Sajavaara (1987), L2 fluency consists of two factors: ”linguistic acceptability and smooth continuity of speech.” Lennon (1990) says that fluency ”reflects the speaker#8217;s ability to focus the listener#8217;s attention on his or her message...rather than...the working of the production mechanisms.” He has paid attention to the listener and the part they play in the communication process.

The fluency of spoken English is every EFL learners#8217; pursue and is routinely used as a non-technical term by teachers and researchers to evaluate the speaker#8217;s performance. Many scholars, linguists, teaching professionals and others have done researches concerning oral fluency and defined fluency from different perspectives. Fluency has taken on both an overarching broad meaning (roughly parallel to the notion of global proficiency) and a componential narrow meaning (as one skill or ”type” of phenomenon of speech among many). (Y. Zhang, 2006).

1.2 Definitions and classifications of pauses.

Pause is regarded as one of the most significant variables in determining oral fluency. A series of studies conducted in the late 20th century investigated the characteristics of fluency in oral production with a special emphasis on hesitations (Zhao, 2011). By definition, pauses are intervals of time during which the speaker does not contribute to the furnishing of silence. They are interruptions in the flow of speech. (Ali, 2004). In most cases, the cut-off point has been utilized to define the concept of pause. Raupach in 1980 and Zhang Wenzhong in 2000 both adopted 0.3 seconds as the cut-off point to define pause. That is, define pause as a break or filler of equal to or longer than 0.3 second, mainly involving filled and unfilled pauses.

There are many kinds of classifications of pauses. Most of them classify pauses into filled pauses and non-filled pauses (or silence). (Lennon, 1990; Riggenbach, 1991).

2. Empirical studies on pauses