Coverbs in Chinese, a class of words whose category status appears intermediate between verbs and prepositions, raise interesting questions for the online processing of category assignment. For constructions like 安娜在圖書館 Anna zai tushuguan (Anna is in the library) and 安娜在圖書館讀書 Anna zai tushuguan dushu (Anna is studying in the library), a common analysis is that the category status depends on the existence of a verb later in the clause: the coverb is a preposition if there is a main verb after the coverb phrase, but a verb otherwise. This analysis poses problems from the processing perspective, given the assumption that words are immediately processed when they are inputted into a processor.

Two groups of coverbs are used to study the online processing of coverb constructions: optional-VP coverbs and mandatory-VP coverbs. The coverbs phrase of optional-VP coverbs can stand alone as a predicate, while mandatory-VP coverbs require a following verb phrase as in 安娜從學校出發 Anna cong xuexiao chufa (Anna set off from the school.) Optional-VP coverbs are temporarily ambiguous between 'prepositional' constructions with a verb continuation and 'verbal' ones with a noun continuation. Corpus data show that mandatory-VP coverbs occur 100% in the [coverb + N + V] construction, while for optional-VP coverbs, the frequency of [coverb + N + V] is higher than [coverb + N]. A norming test showed that the [optional-VP coverb + N1 + N2] construction is rated as more complete than [mandatory-VP coverb + N1 + N2], and [optional-VP coverb + N1 + V] was more complete than [optional-VP coverb + N1 + N2]. A self-paced reading experiment showed that the reading time of N2 in [optional-VP coverb + N1 + N2] is significantly longer than for V in [optional-VP coverb + N1 + V]. The reading time of the final noun in [optional-VP coverb + N1 + N2] is also longer than that in [mandatory-VP coverb + N1 + N2]. The results suggest that [optional-VP coverb + N1] is initially analyzed by the processor as [P NP], based on frequency considerations, then reanalyzed as [V NP] when a verb continuation is not encountered. The corpus findings suggest that the initial analysis is chosen on the basis of frequency.

The results show that coverbs do not form a homogenous category: the processor processes optional-VP coverbs and mandatory-VP coverbs differently. Mandatory-VP coverbs functions consistently as prepositions, while optional-VP coverbs can be verbs or prepositions. The online processing perspective provides support for the view that some coverbs have dual status as verbs and prepositions.

This study resolves the conflict between the common analysis of coverb status and the processing problem of category assignment depending on a later verb. It builds up a link between processing and grammar that is important as category assignment is crucial to structure building and sentence comprehension.