Lexical availability and grammatical encoding scope during spoken sentence production.

Three sentence production experiments investigate the relationship between lexical and structural processing scope. Speakers generated sentences with varying phrase structures in response to visual displays (e.g., The dog and the hat move above the fork and the tree/The dog moves above the hat and the fork and the tree). On half of the trials, one of the pictures in the arrays was previewed. Filler sentences varied preview position and sentence structure from trial to trial. When speakers could not anticipate the position of the previewed picture in the upcoming sentence (Experiment 1), preview benefit for pictures corresponding to the second noun to be produced was limited to pictures that fell within the sentence-initial phrase. When the linear position of the previewed picture was predictable, preview benefits were observed for the second noun to be produced, irrespective of phrase position (Experiment 2). However, no preview benefits were observed for the third noun to be produced (Experiment 3). In contrast, significant effects of initial phrase structure were observed in all experiments, with latencies increasing with initial phrase length. The results are consistent with speakers operating a phrasal scope for structural planning within which the scope of lexical access can vary.