He further remarks, "There is excellent reason to believe that it is literally true that the result of two hours' tests properly chosen from those already tested gives a better diagnosis of an educated adult's general intellectual ability than the result of the judgments of two teachers or friends who have observed him in the ordinary course of life each for a thousand hours."[14] Interesting applications of tests of this general character have been reported by Scott. Workers of various kinds, such as salesmen and clerks, were graded by their employers or supervisors on the basis of their actual ability at their task. It was possible in some cases to get very accurate objective measures of ability to sell goods, etc., by keeping records of achievement over a considerable period of time. These objective measures have been compared with the results of psychological tests administered at the time the men were employed. Positive correlations ranging in several instances as high as .80 to .90 were secured. This means that ability in the performance of the particular mental tests used was a very reliable sign of ability in the field. Various instances similar to these have already been described in Chapter 5.
3. If, as seems quite likely, it be ultimately demonstrated that there are some characteristics, aptitudes and capacities that depend directly on congenital endowment, special nervous and sensory characteristics of a valuable kind, we may mark off another group of occupations for which particular individuals are well adapted, though not exclusively so, by original nature. Among the traits which have been said to occur in some such direct hereditary way, or as the result of unexplained mutation or deviation from type, are: mathematical aptitude, ability in drawing, musical composition, singing, poetic reaction, military strategy, chess playing. Maternity, as a vocation, is of course strictly sex limited. Pitch discrimination seems to depend on structural factors which are not susceptible of improvement by practice. The same may be said of various forms of professional athletic achievement. Color blindness seems to be an instance of the conspicuous absence of such a unit characteristic. "Poets," it is said, "are born, not made." Many of these apparent unit characteristics are so relatively independent that they often occur in quite surprising degree in individuals who are otherwise imbecilic. Mathematical, musical, graphic and decorative aptitudes, mechanical memory, and certain types of manual dexterity and mechanical cunning are frequently exhibited by the _idiot savant_. By the _idiot savant_ is meant an individual who is in most respects mentally defective, who perhaps cannot dress himself, cannot adequately learn to speak or write, but who possesses some particular ability to a surprising degree. Such individuals may be able to perform on various musical instruments, to compose music, to sketch designs and objects in an imitative manner, to remember long lists of disconnected names or numbers, to weave acceptably such articles as rugs and scarfs, or to construct complicated mechanical objects such as furniture, pumps, and sailing vessels.