Psychophysics of reading - VII. Comprehension in normal and low vision

1. This is the seventh in a series of papers describing the role of vision in reading. In the previous studies, we have relied on a subject's fastest reading rate as a psychophysical measure of performance, but comprehension is the ultimate goal of reading. In this paper, we ask how comprehension depends on reading rate and we evaluate comprehension as a psyschophysical measure of reading performance. 2. Subjects read passages that drifted across a TV screen at rates ranging from 10 to 450 words/min. Comprehension was assessed by multiple-choice questions. There were 109 subjects with normal vision and 24 subjects with low vision. 3. Normally sighted subjects showed roughly constant comprehension for rates less than 200 words/min (roughly 2/3 of their fastest reading rates). The view that reading comprehension deteriorates at very slow rates was not supported. Above 200 words/min there was a steady decline in comprehension. However, the lack of a sharp transition from good to poor comprehension means that comprehension is a poor psychophysical measure. 4. When low-vision subjects read at 2/3 of their fastest reading rates, most of their comprehension scores (21 out of 24) were within 1SD (standard deviation) of normal scores. This encouraging result emphasizes the need for prescription of reading aids, even for people with severely impaired vision.