Abstract In this paper, we introduce the notion of positional differential argument marking, a pattern in which the use of argument-coding devices, such as flags or indexes, is contingent upon the linear position of arguments in the clause. Compared to factors such as animacy and referentiality, the impact of word order on differential argument marking is understudied. In order to fill this gap, we compiled and annotated a dataset of 93 PDAM patterns, identified in a genealogically and areally diverse convenience sample of 70 languages. Most patterns involve a competition between a default, or zero, form and a non-zero form, but word order was found to affect argument indexing and argument flagging in a non-identical way. Non-zero indexing is more likely in the case of preverbal arguments. Non-zero flagging is favored in verb-edge orders and also when the argument is used in a non-default position. We hypothesize that this distinction reflects avoiding higher costs in processing referents in the discourse in the case of indexing, but more efficient comprehension of the clause in the case of flagging.
Seržant et al. (Sat,) studied this question.