The Effect of Typography upon the Perceptual Span in Reading

Abstract

In the reading situation, the amount of material perceived at each fixational pause is known as the perceptual or fixation-span. The material perceived at any one fixation is greater than the words or letters within the area of clear vision which covers only three or four letters. Dodge points out that this area of clear vision merges into a less clear and less distinct peripheral area.x There are no sharp boundaries between the two areas. In reading, one fixates an area, not a point. As emphasized by Dodge, practically all the significant stimulation of the retina in any reading pause is extra-foveal. Peripheral vision has an important r6le in reading. In the unclear vision to the right of a fixation it is possible to distinguish vague word forms (outlines of words). For words that are close to the area of clear vision, the word-forms are frequently clear enough to be perceived without direct fixation. The more vague word-forms in the more remote regions of the peripheral vision provide a pre-fixational beginning of perception and act as guides to subsequent fixations. seems probable that the normal reading pause represents a comparatively late moment in the total process of perception of the fixated object.2 The degree to which peripheral vision is utilized by the reader is an important determinant of perceptual span. For instance, it is probable that the proficient reader makes maximum use of cues in peripheral vision in reading easy narrative prose. Certain factors appear to condition the utilization of peripheral vision in reading. It is obvious from experimental evidence that the extent of the perceptual span is partly determined by the complex central processes of apprehension and assimilation. Abundant data show that, as the requirements of comprehension increase, more and longer fixational pauses are required. This means a smaller perceptual span.