This paper presents Phase III of an 11-year longitudinal study on a Japanese-English interpreter, examining what happens to his Lα (Japanese) and Lβ (English) neuro-linguistically (brain activation and structural change). The theoretical framework for this study is based on the Complex Dynamic Systems Theory (CDST, henceforth), which is a combined transdisciplinary label for the Complexity Theory (Larsen-Freeman, 2017) and the Dynamic Systems Theory (de Bot, Lowie, and Verspoor, 2007) and shares the same view that language progression is adaptive, chaotic, complex, dynamic, non-linear, and variable in nature (Mitchell et al., 2019). In comparing the CDST to a static model of language development, Dornyei (2014) argues the importance of including a time scope. This makes straightforward outcomes among variables in the non-dynamic model rather complex because each variable changes over time, impacting the outcome and resulting in an endless chain reaction. The data collected include fNIRS (functional Near-Infrared Spectroscopy) brain activation data, using a Shimadzu OMM-3000 when the interpreter engaged in a verbal fluency task. The results are presented on whether or not accumulated experiences impacted the existing language connectome in the interpreter's brain.
