Visual signals vertically extend the perceptual span in searching a text: A gaze-contingent window study.

This study investigated the effect of visual signals on perceptual span in text search and the kinds of signal information that facilitate the search. Participants were asked to find answers to specific questions in chapter-length texts in either a normal or a window condition, where the text disappeared beyond a vertical 3° gaze-contingent region. The texts either contained no signals, paragraph marks, or headings that did or did not inform about the text content, that is, topic headings or fake headings. The information conveyed by paragraph marks and topic headings both proved to be very helpful to the search process. Moreover, the results revealed a larger perceptual span for the signaled texts than for the unsignaled ones. The results are taken as evidence for the existence of a text layout span in text search which is larger than the span for letter and word processing, and includes the useful typographical information on the printed page.