Putting second language in context: Effects of second language learning context on behavior and gray matter structure
Open Access
- Author:
- Legault, Jennifer
- Graduate Program:
- Neuroscience
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 08, 2019
- Committee Members:
- Ping Li, Dissertation Advisor/Co-Advisor
Ping Li, Committee Chair/Co-Chair
Stephen Jeffrey Wilson, Committee Member
Kathryn Suzanne Scherf, Committee Member
Nanyin Zhang, Outside Member - Keywords:
- Neuroimaging
Second language acquisition
Learning context - Abstract:
- Second language learning and experience has consistently been shown to be associated with changes in brain structure and functional activity. Converging evidence from structural and functional neuroimaging studies suggest that the timing, extent, and nature of L2 experience may impact these experience-based brain changes. Research on the timing of L2 learning has indicated that adults who learn an L2 later in life tend to learn less effectively as compared to child learners, possibly due to the dynamic interactions between the native language (L1) and L2. Further studies have suggested that differences between how the L1 and L2 are learned may help explain this discrepancy in L2 learning performance in adults and children. This leads to the main research questions of the current dissertation: what are the behavioral and structural effects of learning an L2 in a manner consistent with L1 learning? How does this differ from typical classroom and paired association L2 learning contexts, which are the main methods of instruction we currently use? The current dissertation examines the effects of L2 learning context upon L2 learning performance and gray matter structure in adults, and integrates these novel findings with literature from various behavioral, functional, and structural imaging studies. Specifically, Study 1 examines changes in cortical thickness (CT) and gray matter volume (GMV) across two semesters of L2 Spanish classroom learning. Our findings indicated that CT increased in the left ACC and right MTG after L2 learning and CT increase in the left ACC was correlated with its functional connectivity with the MTG (Grant et al., 2015). These findings indicate that intermediate-level L2 lexical development is associated with both functional and structural changes in brain regions important for cognitive control and semantic processing. Study 2 examines changes in CT and GMV in response to different learning contexts for short-term L2 vocabulary learning. We compared structural changes for learning with paired picture-word (PW) association versus learning within virtual environments (VE) and non-trained controls. Our results show 1) CT and GMV increased in regions implicated in a language control network for both L2 training groups, and 2) CT in the right IFG was associated with L2 training performance for the PW group, whereas CT in the right IPL showed a positive correlation with L2 training performance for the VE group. Our findings indicate that short-term L2 training leads to changes in brain structure, which vary based on L2 learning contexts and individual differences in cognitive ability. Study 3 examines individual differences in L2 performance during vocabulary learning in both immersive virtual reality (iVR) and word-word (WW) paired association. Our results indicate a main effect of learning context such that the iVR group outperformed the WW. These results seem to be driven by effects from the less successful learners, who showed a significant benefit of iVR instruction as compared to WW as compared to the successful learners who showed no group differences. These finding have broad implications towards L2 education, particularly for those who struggle in learning an L2. Study 4 is a preliminary study that expands on study 3 by using a between-subjects design to examine structural changes in the brain in iVR versus WW learning. Our behavioral findings indicate no overall effects for L2 learning accuracy as a function of L2 learning context. Our sMRI findings indicate that only the VR group showed significantly greater increase in GMV in the left IPL and ACC as compared to the WW group. Further, L2 performance for the WW group was associated with CT in the left IFG, while L2 performance for the VR group was associated with GMV in the right ACC. Overall, the findings of the current dissertation provide considerable support for the concept that L2 learning context plays a significant role in L2 learning efficacy and L2 experience-dependent neuroplasticity. Behaviorally, virtual environments were shown to be more effective as learning platforms as compared to paired association-based learning conditions. Structurally, experience-dependent gray matter increases in the left ACC and IFG tended to occur across classroom-based, iVR, and PW L2 learning conditions. On the other hand, learning in virtual environments uniquely was associated with structural changes in the IPL, a region functionally implicated in effective L2 learning. This dissertation provides the first systematic examination on the effects of L2 learning context on both behavioral performance and gray matter structure.