Cross-clause planning in Nungon (Papua New Guinea): Eye-tracking evidence.

Hundreds of languages worldwide use a sentence structure known as the "clause chain," in which 20 or more clauses can be stacked to form a sentence. The Papuan language Nungon is among a subset of clause chaining languages that require "switch-reference" suffixes on nonfinal verbs in chains. These suffixes announce whether the subject of each upcoming clause will differ from the subject of the previous clause. We examine two major issues in psycholinguistics: predictive processing in comprehension, and advance planning in production. Whereas previous work on other languages has demonstrated that sentence planning can be incremental, switch-reference marking would seem to prohibit strictly incremental planning, as it requires speakers to plan the next clause before they can finish producing the current one. This suggests an intriguing possibility: planning strategies may be fundamentally different in Nungon. We used a mobile eye-tracker and solar-powered laptops in a remote village in Papua, New Guinea, to track Nungon speakers' gaze in two experiments: comprehension and production. Curiously, during comprehension, fixation data failed to find evidence that switch-reference marking is used for predictive processing. However, during production, we found evidence for advance planning of switch-reference markers, and, by extension, the subjects they presage. We propose that this degree of advance syntactic planning pushes the boundaries of what is known about sentence planning, drawing on data from a novel morpheme type in an understudied language.