Are benefits of second language acquisition and Language testing a two-way street?

This paper's prime aim is to argue that the relationship between second language acquisition (SLA) and language testing (LT) is a bilateral commitment with reciprocal interests and benefits. By showcasing examples of how these two fields benefit from each other, we would argue that more collaborative research between experts in the two areas can help fill some important research gaps in the relevant fields. After an introduction based on Shohamy (2020), the paper will have two main parts. In the first part, we will discuss some studies (Inoue, 2016; Inoue & Lam, 2021) in LT research which have useful implications for SLA researchers; they demonstrate the contributions of LT to SLA in terms of the validation of research instruments and variabels for analysing learner performance. In the second part, we will summarize some of the key findings of SLA research that have significant implications for language testing. After presenting a brief overview of these areas, we will focus on fluency research and the contribution it has had to the field of language testing. Recent research (e.g., Tavakoli, et al., 2017; 2019; 2020) has shown that using a SLA perspective to analyzing spoken performance is an effective and reliable way of validating English as a second language test. The findings of these studies suggest that only few aspects of fluency distinguish speakers at different levels of proficiency. These results further indicate that fluency ratings fail to distinguish speakers at higher levels of proficiency, and therefore the rating allocated to the speakers often reflects raters' evaluation of other aspects of performance. Finally, the talk is concluded with a more up-to-date overview of the two-way street between SLA and LT by Nakatsuhara, Inoue and Khabbazbashi (2021).