Lexical bloom, syntactic retreat: examining complexity trade-offs within Classical Chinese evolution across two millennia

Abstract The Complexity Trade-off Hypothesis suggests that when one language domain becomes more complex, another tends to simplify to maintain an overall balance of complexity in languages. Previous studies sought to test such trade-offs across languages, implying the equal complexity across languages. However, this assumption has been increasingly questioned. Furthermore, little attention has been given to diachronic changes and interactions in lexical and syntactic complexities, especially within ancient and non-European languages. Against this backdrop, this study explored the evolution of lexical and syntactic complexities and their possible trade-off in Classical Chinese over two millennia. Based on entropy and dependency distance metrics, we found a marked increase in lexical complexity alongside a decrease in syntactic complexity. Our findings provided support to the existence of trade-offs in an individual language and broadened the scope of the complexity trade-off analysis in historical language contexts.