The Span of the Effective Stimulus during Fixations in Reading.

This study investigated the effect of two classes of variables on a person's performance: the size of the window within which normal text was displayed and the type of information present in the display beyond the boundaries of the window. Six junior and senior high school students, identified as being among the best readers in their school, were used as subjects. Each subject read sixteen 500-word passages taken from a high school psychology text. Each passage was divided into six pages, displayed a page at a time, double-spaced, for the reader. Six mutilated versions of the passages were also prepared. For two of these versions each letter or number was replaced with an X. For two versions each letter or number was replaced with a letter or number which tended to be visually confusable with it. In the final two versions each letter or number was replaced with a letter or number not usually confused with it. Eight window sizes were used: 13, 17, 21, 25, 31, 37, 45, or 100 character positions on the line fixated. Results indicated that there is a clear effect due to window size. Reducing the window to thirteen characters increases the fixation duration by 30 percent, decreases the saccade length for forward saccades by 26 percent, and increases reading time by 60 percent, as compared to a window size of 100 character spaces. (WR)