Modern industrial machinery, technologies, and organization, and the character of many expanding mass trades and occupations impose heightened demands on the intellectual components of work. In many expanding worker occupations, the nature of work is changing before our very eyes. Thus, in setting up or repairing various mechanical devices, machinery, and equipment, 60 to 80 percent of work time is devoted to looking for errors and only 40 to 20 percent is spent on the actual correction of errors.