Do verb bias effects on sentence production reflect sensitivity to comprehension or production factors?

Speakers should be motivated to produce easy-to-understand sentences, but they must successfully say sentences that are harder to produce. Four experiments assessed how verb bias influences the mention of the optional "that" in sentence-complement structures. Without the "that", such sentences can be incorrectly interpreted as including direct objects (garden paths), and especially so after direct-object-biased verbs (compared to embedded-clause-biased verbs). But direct-object-biased verbs are rarely produced as sentence-complement structures, and so they might be harder to produce as such. Experiments 1 and 2 show that speakers mention the "that" more after direct-object-biased verbs than after embedded-clause-biased verbs. Experiment 3a shows that sentences with verbs biased toward neither direct objects nor embedded subjects were often produced with the "that", and Experiment 3b shows that postverbal noun phrases after neither-biased verbs are interpreted as direct objects less than direct-object-biased verbs and so should cause a milder garden path. Thus, frequent "that" mention is not sensitive to the tendency of a verb to be followed by a direct object, but by how rarely the verb has been produced in the formulated structure.