Occasionally it is possible to illustrate in nature, to the eye of the man untutored in the derivation of scientific laws, the form of this distribution. This happens, for example, when a very large flock of birds rises and passes overhead, during migration. Being tested in flight, the birds will be seen distributed somewhat as suggested in Figure 2. Not all are equally swift and enduring, but they deviate from a single type or mode—the great median mass of birds, which are typical of this species, in respect to the function of flight.
The same phenomena of distribution appear if a thousand wild horses run a race, or if a hundred unselected swimmers swim in competition. They appear whenever non-select organisms of a single species are submitted to an adequate test or measure of any function of endowment. The curve approximates that form which mathematicians tell us results when an infinite number of factors act together in an infinite number of ways.
We have spoken thus far of the distribution of individuals in a single kind of performance. What does quantitative psychology teach with respect to the combination of performances in a given personality? Is it true, as folk-wishes would have it, that abilities are distributed among us by a law of compensation? Is the slow man’s slowness offset by accuracy? Does the quick learner lose his learning more readily than the slow learner? Is he who excels in arithmetic likely to be surpassed at spelling? The general consideration of these questions, which form the topics of this volume, will be found in the chapter which follows. It will be seen that there is no law of compensation in human ability, however much we may long to find it there.
Fig. 2.—Flight of birds, illustrating distribution in ability to fly. (Schematic.)
As for the origin of talents and defects, psychology teaches that mental endowment in human beings is conditioned by ancestry, just as other traits of organisms are. Mental capacities are inherited through the germ-plasm. A child is gifted (if he is so) for the same reason that he is an Eskimo (if he is one)—because some or all of his ancestors carried those traits in their germ-plasm, and the combination of them in just that way was possible.
REFERENCES
Meumann, E.—Vorlesungen zur Einführung in die experimentelle Pädagogik; Engelmann, Leipzig, 1914.
Seashore, C.—Measures of Musical Talent; Columbia Graphophone Company, New York, 1919.
Stern, W.—Die differentielle Psychologie; Barth, Leipzig, 1911.