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Vision SpanVision Span or perceptual span is the width and height at which the human eye has an effective focus area to view text. The human eye can see approximately 120 degrees of arc. However, most of that arc is peripheral vision, the area outside of the area at which the human eye has effective cone cell resolution in the macula. The area that is actually in sufficent focus because of resolution limits is approximately 6 degrees of arc, which is typically enough to see three to five words wide and high when printed text is held at approximately 18 inches from the eyes. The brain creates the illusion of having a greater span of vision by automatically and unconsiously moving the center of vision into any area of interest in the field of vision. During reading processes readers will fail to recognize a word unless they are fixating within three to four character spaces of the word (Rayner, 1975). The same is true for speed readers and skimmers. Speed readers cannot answer questions about a main point or detail, if they did not fixate directly on it or within three character spaces of it (Just and Carpenter 1987). When a text is removed whilst reading, readers can only accurately report upon the word they were fixating upon or the next one to the right (McConkie and Hogaoam 1985). There is no evidence from eye movement research that individuals are making predictions of text based upon hypotheses about the words in the periphery so that they can skip over or spend less time on unimportant or redundant words (Rayner, 1975). Most speed reading courses claim that the peripheral vision can be used to read text. This claim has been found to be false, because the text is blurred out through lack of visual resolution. At best the human brain can only guess at the content of text outside the macula. There simply are not enough cone cells in the eye to have sufficient resolution to identify words in the periphery around the central area of focus. There is also the problem of the blind spot, an area near the center of vision at which the human eye has no cone cells or rod cells to effectively see anything. It has been suggested, primarily through popular psychology that the fixation span can be stretched through training meta guiding to take in as much as a line for the purpose of skimming or speed reading. This suggestion has found to be false, which goes some way to explain why skimming results in a severely reduced comprehension rate in comparison to normal reading (rauding). Some speed reading courses stress that the human eye has to move very quickly. They also stress that the human eye should move in a pattern to fill in the information that was not properly perceived. The effective limit for scanning speeds based upon the limit of the human eyes resolution is approximately 10,000 words a minute. Such speeds also require great practice, and extremely rapid eye movements. It has been suggested that the readers who achieve such speeds are on the autistic spectrum, such as Kim Peek. References - Rayner 1975. The perceptual span and peripheral cues in reading. Cognitive Psychology, 7, 65-81
- McConkie and Hogaoam 1985. Eye position and word identification during reading. In R. Groner et al's Eye movements and information processing. Amsterdam, Elsevier.
- Just and Carpenter 1987 In Allyn & Bacon's The Psychology of Reading and Language Comprehension. Boston.
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