Blinking as a measure of effort in visual work.

In recent years a controversy has been waged over the validity of frequency of blinking as an index of effort in visual work.1 On the basis of a series of validating experiments, which involved such variables as intensity of illumination, glare, typography, distorting lenses, and duration of work (fatigue), Luckiesh and Moss concluded that frequency of blinking is inversely related to the adequacy of the conditions under which visual work is performed.2 A variety of subsequent experiments by other investigators have, however, failed to substantiate these results.3 While it is true, Hoffman4 and Tinker5 have reported a significant tendency for frequency of blinking to increase in the course of prolonged visual work, and Simonson and Brozek6 have found a significant relation between frequency of blinking and level of illumination, the great preponderance of negative results has led even these investigators to doubt the value of the index. In the experiments just referred to, Tinker failed to find a relation between blinkrate and level of illumination; Simonson and Brozek found no significant relation between blink-rate and duration of work; and Hoffman pointed out that "the statistical determination of a significant difference is not neces-