The longitudinal obseration, from the perspective of Dynamic Systems Theory entails challenge to the generally-held “plateau phenomenon”. Via the five indices in lexical richness, there exist the sequential attractor states and repellor states in the development process. The dynamic characteristic of interlanguage is also proved by connected growers and competitors.
Based on a self-compiled Longitudinal Learner Written Corpus of EFL learners in China (107,907 tokens), this study conducts a longitudinal probe into their lexical richness development. The criterion for advancement is set by their institutional status—the development through 6 semesters. A combination of both quantitative description and qualitative analyses is adopted in the data processing, which is interpreted from the perspective of Dynamic Systems Theory. Through the quantitative description and qualitative analysis of the indices from 3 aspects of lexical richness (consisting of lexical density, lexical variation and lexical sophistication), the findings confirm the dynamic features of lexical development. The dynamicity is shown by the existence of sequential attractor states and repellor states in lexical developmental process, with the first three semesters being more fluctuating and the later part inclining toward linearity. Another dynamic characteristic of the interlanguage lexicon is proven by the identification of connected growers and competitors. The 2000 most-frequently-used words form competitive relationships with academic word list families (AWL) and off-list word families. Lexical density and lexical variation are connected growers, the same being the relationship between lexical density and AWL. The findings show that the developmental patterns of the subjects’ lexical richness display fairly dynamic ebbs and flows, rather than linear ascent or descent. These dynamic features of lexical development serve as a challenge to the notion of “plateau phenomenon”, which is prevailingly held by most researchers.
