EXPRESS: The lexical boost is not an automatic part of sentence production: Evidence from Japanese structural priming.

The lexical boost is an increase in structural priming with overlapping elements like verbs. Residual activation priming theories argue that the boost is an automatic side effect of sentence planning. In contrast, explicit memory theories of the boost argue that it is the result of a non-automatic explicit memory retrieval. These theories were contrasted in Japanese by including a prime memory task in a structural priming study. Structural priming was found for both datives and passives, but no lexical boost was found and one possible reason was that explicit memory for the prime structure was weak. In a follow-up study, priming was found in a sentence completion task, but there was no lexical boost. The existence of abstract priming and the lack of a lexical boost in these studies falsifies theories that argue that verb overlap automatically creates a boost under conditions that exhibit abstract priming.