Inferences about eye movement control from the perceptual span in reading.

Subjects' eye fixations in a target region were examined as a function of how far the eye was from the beginning of a target word on the previous fixation. Prior to fixation of the target word, a letter string in the target location (which was then in the parafovea) was either visually similar or visually dissimilar to the target word. The results indicated that letter information was extracted from the target location when the eyes were at least nine characters from it. However, at such far distances, the parafoveal information extracted affected only the gaze duration on the target word, whereas at nearer distances, it affected both the gaze duration and the firstfixation duration. These data indicated that the decision to adjust the length of a saccade can be made after the decision to move the eye. In addition, the lengths of saccades and times to examine words were positively correlated: a longer saccade onto the target word was associated with longer gaze durations on both the target word and the prior word, and skipping the target word was associated with a longer last fixation on the previous word. .