For military purposes it was desired to know the relation between two types of reaction time tests. These tests were: (1) a simple reaction time test of the usual type, (2) a clock reaction time test in which the subject attempted to stop the moving hand of a clock at a certain predesignated point on the face, by pressing a standard telegraph key. Seashore, Buxton, and McCollom (1940) have reported that certain factors corresponding to motor skills have been isolated in terms of qualitative similarity in the pattern of action, including perceptual activity, involved in various tests rather than to anatomical units such as the dominant sense-field, or even the musculature employed. Seashore, Starmann, Kendall, and Helmick (1941) found that both simple and discriminative reaction times for visual and auditory stimuli are included in a group factor of speeds of single reactions. The same authors, however, warn against extending this factor to include other kinds of reaction time without experimental verification
