Abstract: Working memory capacity and sentence processing are closely related. The capacity-constrained theory argues that there is a general verbal working memory system that supports language processing. Alternatively, the separate processing resources theory states that there are two kinds of working memory systems that support the on-line and off-line language processing separately. The capacity of working memory measured by the Daneman and Carpenter Reading Span Test (1980) only influences off-line language processing.
This study presents an eye-tracking experiment that investigated whether the working memory capacity of adult learners of English as a second language had an effect on the on-line and off-line processing of English sentences. The sentences contained verbs that were temporarily ambiguous between a main verb and a reduced relative clause. Participants were 31 Chinese-English bilinguals who are less proficient English readers.
The reading span test of Daneman and Carpenter (1980) was used to differentiate high-span and low-span readers. The first-pass fixation duration of reading different regions of sentences was used as the index of on-line processing; whereas the regression numbers and total fixation times were used as the index of off-line processing. Results showed that the first-pass durations were significantly different on ambiguous and disambiguated regions between high and low working memory capacity readers; the regression patterns from disambiguated regions to ambiguous regions and to subject noun phrase regions between high and low working memory capacity readers were similar; the total fixation times were significantly different on the ambiguous and disambiguated regions between high and low working memory capacity readers.
These results suggest that different working memory capacity affects the on-line as well as the off-line syntactic processing of syntactically ambiguous English sentences for less proficient second language readers. Furthermore, these results support the capacity-constrained theory of working memory.

Key words: working memory, syntactically ambiguous English sentences, syntactic processing