Is Speech Planning More Linearly or More Hierarchically Incremental in Consecutive Interpreting?

When people produce sentences, they can either proceed incrementally word by word (Linear Incrementality) or by preparing larger conceptual-syntactic frameworks (Hierarchical Incrementality). While the scope of advance planning is generally affected by processing load, it remains unclear how bilingual speakers adapt their planning strategies to the heightened demands of L2 production, particularly in cognitively challenging conditions. This study examined the effect of structure-related load on bilinguals' planning scope in consecutive interpreting. Thirty-nine Chinese-English interpreter trainees interpreted sentences that varied in source-target symmetry (symmetrical adjectival modifiers vs. asymmetrical prepositional phrases) and structural length (short vs. long). Planning scope was assessed through reordering rates, based on the assumption that the order of items can be reversed only when they are processed in the same unit. Results showed that both asymmetry and length increased the probability of reordering, indicating greater reliance on hierarchical incrementality. Further analyses of dependency relations and disfluencies revealed that interpreters expanded the planning scope before articulation to reduce downstream integration costs and facilitate economy-driven reformulations, whereas linear incrementality minimized initial planning effort but often at the expense of fluency. Overall, the findings support the proposal of a flexible and adaptive planning process.