Using Mental Set to Change the Size of Posner's Attentional Spotlight: Implications for how Words are Processed in Visual Space
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The present thesis investigated how words are processed within the context of visual search. Both explicit and implicit measures were used to assess whether spatial attention is a prerequisite for words to undergo processing. In the explicit search task, subjects searched a display and indicated whether a word was present or absent among nonword distractors. In the implicit task, priming was employed to index word processing. Subjects viewed the same search displays that were used in the explicit task, however, the displays were presented briefly and were followed by a single target letter string to which subjects performed a lexical decision. In Experiments 3 through 6, in which the target was always presented at fixation, no priming was evident. In Experiments 7 and 8 when the location of the target moved from trial to trial, priming was observed. It is argued that attentional resources are narrowly allocated to a location in visual space when target location is certain but diffusely allocated when target location is uncertain. Furthermore, processing only occurs for words that fall within the suffusion of this strategically pliable attentional beam. The results are also interpreted within the domains of perceptual cuing and attentional capture.