Background and Aim: L۲ proficiency modulates the
ERP signatures associated with L۲ syntactic processing, with high proficient L۲ learners' often displaying of L۱-like patterns, whereas the
ERP responses of low-proficient L۲ learners display quantitative and qualitative differences (Diaz et al., ۲۰۱۶). The different patterns of activation could mainly be ascribed to the age of acquisition, proficiency level, and type of instruction (implicit vs. explicit) (Steinhauer et al., ۲۰۰۹). Difficulties in lexical/semantic processing in L۱ elicit central/posterior bilaterally distributed negativities (N۴۰۰) and syntactic violations elicit a
P۶۰۰ component which is associated with the activation of procedural memory (Osterhout et al., ۲۰۰۸). Methods Two groups of Persian-English bilinguals (L۱=Persian, L۲=English; N=۱۰ high-proficient, N=۱۰ low-proficient (pre-intermediate levels); Gender Female; mean age=۲۵.۵۰ years, SD = ۵.۰۹ years, age range = ۱۹-۳۵ YoA) who learned English as a foreign language (EFL) after the age of ۱۵ under explicit instruction were compared. Within the
N۴۰۰ time window (۳۰۰-۵۰۰ms) and the
P۶۰۰ time window (۵۰۰-۷۰۰ms), ERPs to the violated words were compared between the two groups across six different conditions including a visual stimulus task of ۲۴۰ English sentences with three different experimental conditions (English sentences including violated regular past forms or phrase structure rules or final-word semantic violation) and three control conditions (sets of correct sentences for each experimental condition). ANOVA was used to investigate the performance of each group against task conditions and t-test was used to compare the performance of the two groups on each condition. Results: The main purpose of this study was to investigate the extent the second language (L۲) proficiency accounts for native-like syntactic and semantic processing in two groups of Persian-English bilinguals when their age of acquisition was after the puberty and the type of instruction for learning English was explicit. Conclusion: Results showed that upon processing the syntactic violation conditions, more native-like patterns of scalp activity were elicited from the high-proficient subjects, despite their late age of acquisition and undergoing explicit instruction, addressing their application of more procedural and automatic memory systems. However, less proficient learners have shown different components in a number of regions with N۴۰۰s or N۴۰۰-like posterior negativities while processing the syntactic violations; this could refer to the initial reliance on the declarative memory system and less automaticity for syntactic processing at lower levels of L۲.
