Another important method of measurement takes advantage of the fact that, up to a certain point in growth, achievement is a function of maturity. The average four-year-old child can repeat immediately after one hearing, a sentence of 12 syllables; the six-year-old, 17 syllables; the eight-year-old, 19 syllables; while at ten, thirteen, and sixteen years the memory spans are 21, 24 and 28 syllables respectively. That is to say, irrespective of other conditions, memory span is a function of age. This is true of most intellectual operations up to a point which ranges from 11 to 16 years, according to the nature of the process.
It is thus possible in the case of, say, an adult epileptic whose immediate memory enables him to repeat but 17 syllables, to say that, although he is chronologically an adult, his memory span is only that of an average six-year-old child. Other capacities or disabilities of a patient can similarly be expressed in terms of developmental units or years of growth.
During recent years rapid progress has been made in the standardization of capacity tests in terms of developmental units, and new standardizations are from time to time reported and adopted.
The ideal psychographic technique would call for standardized tests for each of those component factors which comprise that highly elaborate complex we call personality. Psychological research is still far from realizing this goal, but advance is being made so rapidly that close specialization of interest and cordial collaboration of psychiatrists and psychologists are required in order that satisfactory progress and application in this important field may be assured.
A notable step in the science of mental measurement was made by Binet and Simon when they attempted, on the basis of empirical investigation, to extend miscellaneous achievement scales from the third year up through the later years of childhood and youth to maturity. Accepting a year of growth as a convenient unit of division, experimental research enabled these investigators to establish at each age level a group of intelligence tests which could be accomplished by the majority of children at that age, but failure in which characterized the average child of younger ages. Special effort was made to exclude such acts as would depend on education and training rather than simple psycho-physical growth.
The practical value of such an intelligence scale was readily appreciated, and the original scale soon underwent, at the hands of numerous investigators, such revisions, adaptations, extensions and wider standardizations as would render it more reliable and comprehensive. The most widely used scale is that known as the Stanford revision formulated by Terman and his associates. Directions for the use of the Stanford revision will be found in Appendix V, Part III, of this Manual.
Other adaptations, notably the Point Scale of Yerkes and his collaborators,1 have been found useful by many workers.
Such intelligence scales, and the psychographic methods already discussed, afford the most reliable means of determining intellectual make-up and of revealing and measuring mental deficiency. In applying these tests to cases of psychotic conditions it is, of course, necessary to guard against mistaking temporary disability of acute psychotic states or acquired disability in states of dementia for inferiority of original mental endowment. In the presence of active psychotic manifestations these tests are not to be applied, but one should rather wait until the active manifestations have subsided and the patient is sufficiently composed to give full cooperation.
The intelligence scales described above are used in individual examinations which require the devotion of half an hour to an hour or more to each subject. Many occasions arise in which it is desirable to make intellectual ratings of large numbers of individuals, for which purpose the time-consuming individual methods are inexpedient. Accordingly for the examination of army recruits, selection of industrial employees, classification of school children, etc., group tests have been devised. A number of standardized group tests will be found described in Appendix VII, Part III, of this Manual.
1 Yerkes, Bridges and Hardwick. A Point Scale for Measuring Mental Ability. Baltimore, 1915.
Limitations of group tests are obvious. Although success in them may be taken as reliable indication of the subject's mental competence, failure may be due to a great variety of factors. Illiteracy, sensory defect, unfamiliarity with the language of the instructions, physical impediment, and psychotic conditions may, in the intellectually competent, cause the showing to resemble that of the mentally deficient. For these reasons subjects who fail in group tests should always be submitted, before decision, to individual examination. Group tests afford a useful means of indicating those most likely to require closer individual study.
The tests described up to this point relate chiefly to the intellectual or cognitive aspects of mental life, and deal mainly with capacity to achieve in those multifarious adaptations which have as their end product what we call intelligent conduct. There are, of course, many other traits of personality that have high psychiatric importance, and for which methods of measurement are also desirable. The relative strength of instincts and fundamental trends, the affective make-up, volitional characteristics, the focalization of effort, degree of accessibility, moral habits, character trends, the strength of determining tendencies, eccentricity of values - these and other non-cognitive aspects of the mental make-up may assume a dominant role in the clinical picture. Measurement in these fields is far less advanced than in the determination of intelligence and capacity, and the more strictly cognitive functions such as learning, memory, perception, language ability, judgment and reasoning. There are, however, certain valuable quantitative aids to diagnosis and description which it may often be advantageous to employ.
Association tests may be found useful in studying disturbances of the flow of thought, and they have been used in the technique of psychoanalysis. For whatever object employed, it would seem advisable to make use of a standardized procedure. For this reason the test developed by Kent and Rosanoff is recommended. This test has been applied to one thousand normal subjects, and all reactions thus obtained arranged in frequency tables for all stimulus words. The technique and the necessary tables are given in Appendix VI, Part III, of this Manual.
In this test normal subjects seldom give over 10% individual reactions; psychotic subjects very often give over 25%. Among the individual reactions are contained almost all those that are of pathological significance. Moreover, certain varieties are to be distinguished among the individual reactions which are more or less characteristic of the various clinical types of mental disorder.
Standards have also been made available for the ages of childhood from four to fifteen years. Feeble-mindedness is recognizable with the aid of this test, and its degree may be roughly determined by reference to the standards for normal children. This test is sometimes capable of revealing mental abnormality where other methods of examination yield only negative results.
Related to the association tests is the psychoanalytic technique. The examiner's familiarity with the case will suggest special stimulus words. These may be given together with those employed in determining community of ideas, being introduced, say, after every fifth or tenth one. In such cases it is also advisable to record in each instance the reaction time in fifths of a second by means of a stop-watch or kymograph. " Complexes " are said to be indicated either by abnormal types of reaction or by lengthened reaction times.
Further ways in which psychological methods may be utilized to advantage in fields bordering on psychiatry are to be found in the fields of psycho-pathology and pharmaco-psychology. Thus in recording the shifting phases of manic-depressive psychoses laboratory technique may enable the observer to derive quantitative measures of psychomotor excitement, retardation and inhibition. In the study of the immediate effects of toxic substances, which has since the early days of experimental psychology possessed a certain interest for the psychiatrist, stimulation, depression, inhibition, secondary reaction, latent period of action, and similar facts may be given definite and objective expression through the use of standardized capacity tests and other technical devices of the psychological laboratory. In this way also qualitative analysis of the incidence of the toxic influence may be furthered.
Training in cases of mental deficiency and re-education in cases of mental deterioration may be expected to succeed only in so far as they conform to general principles of educational psychology, which govern here as well as in all learning. The specificity of habit formation, for instance, is fundamental; and efforts that do not take this into account are likely to meet with disappointment; success is attained only in so far as particular desirable habits are acquired and undesirable ones inhibited. The original nature of man, which bulks so large in discussions of general educational procedure, is no less important in educational therapeutics.
It may not be amiss to point out in theoretical as well as clinical relations the reciprocal influence of the concepts of psychiatry and psychology. Differential psychology, through its measurement of the degree and distribution of individual differences in mental traits, has exerted, along with other biological sciences, a wholesome influence in modifying the older psychiatric concept of clinical entities. As regards the large group of constitutional disorders, it is more and more realized that the marked disturbances encountered in institutions and clinics represent only the extreme end of the curve of distribution of the symptoms involved. The frequent resort in recent years to such diagnoses as "allied to dementia praecox" and "allied to manic-depressive psychoses" marks the professional recognition of the many borderline cases intervening between the average and the extreme deviations. The wholesome tendency in modern psychiatry, to refuse to draw sharp lines of demarkation and to recognize many of the conditions met with in the psychiatric clinic as being anomalies of character rather than diseases in the ordinary sense of the word, is throughout supported by the findings of differential psychology.
On the other hand, modern psychology has been distinctly influenced by concepts originating or emphasized in the formulations and practices of psychiatry. The emphasis on psychogenic factors; the exposition of the mechanisms of adaptation, thought, and character formation; the insistence on the energic character of mental life and conflicts and resolutions of fundamental trends, so conspicuous in modern psychiatry, have had much to do with the advance of theoretical or general psychology from its old structural concepts to its more modern dynamic point of view.