Exploring the role of proficiency as a mediator of the relationship between working memory and text comprehension in the l2

The main purpose of this study is to find out whether there is a relationship between WM capacity and listening/reading, and whether this relationship is mediated by learners' proficiency level in the L2. In addition, with a mixed methods design where the effect of proficiency level is investigated both as a between groups factor but also as a within groups factor, this study aims to make a cross-sectional comparison of different proficiency groups (intermediate and upper-intermediate) at a certain point in time as well as developmental comparison of the same proficiency group before and after instruction. The participants consist of Turkish University students from Çanakkale Onsekiz Mart University. The Working Memory Capacity was measured by, Reading Span Test (English version), Reading Span Test (Turkish version), and Operation Span Test. To measure the participants' reading and listening comprehension, this study made use of the Certificate in Advanced English (CAE). Descriptive statistics, and 2x2x2 mixed ANOVAs were conducted separately on listening and reading scores with time of testing (pre vs. post) as the repeated measures factor, WM capacity (low vs. high), and proficiency level (intermediate vs. upper-intermediate) as between groups factors. The results indicated no significant effects of WM on reading comprehension. On the other hand, its effect on listening comprehension was significant when WM was measured by L1 or L2 RST. Moreover, it was observed that the difference between low- and high-WM capacity learners was greater on the pre-test compared to the post-test for listening comprehension but not for reading comprehension since the interaction between WM and time of testing was significant for the former, not for the latter. Also, when WM capacity is measured by the RST in the L2, the results for listening comprehension indicated a significant interaction between time of testing and WM. However, the difference between the low- and high-WM participants is negligible in the upper-intermediate group in terms of both listening and reading comprehension when WM is measured by the RST in the L1. Results are interpreted in the light of Working Memory Model (Baddeley, 2000), and Declarative/Procedural (DP) Model of language acquisition (Ullman, 2001a, 2001b). Key Words: Working Memory Capacity, Reading Comprehension, Listening Comprehension, Language Proficiency