2. Somewhat more abundant and diversified are those forms of employment for the unspecialized mental competent. This requires only a sufficient degree of intelligence to enable the individual to escape classification as a mental incompetent. One who is capable of earning a living under favorable circumstances, in the absence of aggressive competition and without close supervision, can find his or her level in the "blind alley" occupations. These offer no prospects of promotion to positions of responsibility and skill, and by definition, this group of individuals afford suitable workers for these occupations. They fill the gap between the feeble-minded and that degree of intelligence which the most moderately endowed _average_ individual typifies. Rough clerking and attending, simple personal and domestic service, delivering goods of small value, laundry work of the mechanical sort, supervised manual and agricultural labor, waiting on domesticated animals, standardized and mechanical factory operations, wrapping, cleaning, polishing, petty shop-keeping, running errands and freight elevators, street cleaning, janitorial assistance, etc., are forms of work about equally difficult and satisfying. They do not involve the acquisition of special skill or technical knowledge and they are capable of performance, in the main, by almost any physically able person above the status of feeble-mindedness. We may expect that in the very near future there will be provided standardized scales for the determination of general intelligence of this degree. Even now it is fairly easy to select from a group of children those who, while not positively mentally defective, are nevertheless slow of comprehension, stupid, unable to acquire new knowledge and skill with facility, and perhaps disinclined or unable to form the moral and social habits of honesty, cleanliness, promptness, truthfulness and economy. Since these can fill the "blind alley" occupations with fair satisfaction they should be "guided" into the first available positions of this kind.
Thorndike has advocated a series of tests, experience with which leads him to say:
"Suppose that the general intellectual ability of the dullest men who are able to support and look after themselves (men who though temperate and strong earn say $400 a year in good times in New York City) be represented by a and that of Aristotle or Goethe by _a_+_b_, the difference, _b_, being 100. Then the amount of such ability assigned by the tests alone would not, on the average, vary from the individual's true amount by more than 5; and would not vary therefrom by more than 14 in one case out of a hundred. The 5 and 14 are very cautious estimates, 4 and 11 being probably nearer what such an experiment would in fact reveal."