Although much further research is required before we can identify all the mental functions which are incoherent with general intelligence, we already have some knowledge of the matter, useful for the welfare of school children. Certain abilities are shown repeatedly by different investigators to be relatively independent. Success in music and in representative drawing is very slightly correlated with success in other school subjects. Spelling is far from perfectly predictable from grades in schooling generally. Mechanics is relatively independent. Whereas ability in reading and in arithmetic is highly, but not perfectly, correlated with general competence.
These facts mean that from knowledge of a pupil’s general intelligence we can make very reliable predictions as to his capacity for reading and for arithmetic, somewhat less reliable predictions as to his aptitude for spelling or mechanics, and that our predictions concerning his ability to draw, sing, or play musical instruments should be given without confidence in their reliability, if given at all.
Other kinds of performances, like the management of people, appreciation of a joke, dancing, the management of wild or domestic animals, have not been thoroughly studied in their relation to general intelligence, though these and scores of others which will occur to the reader, might be of great significance for practical psychology, if shown to be somewhat independent talents.
As we have already said, most of the functions performed by human beings are very complex, and capable of analysis. To read, understand, and execute a page of any musical composition is a very complicated performance. The attempt to measure special ability has been the attempt first to scale total performance in the function, and second to scale performance in the various coördinating functions contributing to total result. Thus in the case of musical talent, Seashore has found by analysis a large number of contributing factors, and has actually devised scales of measurement for five of these subsidiary functions.
Measurement more or less adequate can now be made of ability to read, spell, draw, write, put mechanical contrivances together, and calculate. This list does not by any means exhaust the possibilities of measurement in particular functions at present, but exemplifies them. Slowly we are approaching the point of being in position to tell not only how a child stands in general intelligence, but also to indicate his status in regard to special abilities. The “picture” of the total relationship among a person’s abilities is called a psychograph.
XI. THE PSYCHOGRAPHIC PICTURE OF INDIVIDUALITY
A psychograph may consist merely of numerical statements of the individual’s standing in various mental capacities respectively; or it may be presented in the form of a graph drawn from the figures. No standard graph has been agreed upon. Sometimes the method is to present points of deviation from a horizontal line representing the typical performance; sometimes to present the deviations from a vertical line, representing the typical; sometimes to present deviations along the spokes of a “wheel,” the typical being taken as a circumference drawn midway between the center and the perimeter of the circle.
Fig. 3.—The psychograph of a school boy, showing his standing in various mental functions; illustrating use of the horizontal line to denote typical performance. The scores are in terms of mental age. (From Hollingworth’s Judging Human Character. Reproduced by courtesy of D. Appleton and Company.)
Figure 3 is an illustration of the first mentioned mode of presentation. It shows the status of a school boy in various mental functions measured. This boy is 18 years old. In interpreting the psychograph, which is platted in terms of mental age, it must be borne in mind that many of the capacities here included are matured by the age of 16 years. The individual is not, therefore, subnormal with regard to them. This case illustrates some of the difficulties of treating adolescents and adults in terms of mental age.