# Popular Science Monthly/Volume 81/November 1912/The Permanence of Interests and their Relation to Abilities

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* THE PERMANENCE OF INTERESTS AND THEIR RELATION TO ABILITIES
By Professor EDWARD L. THORNDIKE
TEACHERS COLLEGE, COLUMBIA UNIVERSITY
THERE is a wide range of opinion amongst both theorists and practitioners with respect to the importance of the interests of children and young people. These early likes and dislikes, attractions and repulsions, are, by some, taken to be prime symptoms of what is for the welfare of the individual or even of the species. By others they are discarded as trivial, fickle, products of more or less adventitious circumstances, meaning little or nothing for the nature or welfare of any one. It seems, therefore, desirable to report whatever impersonal estimates of the significance and value of interests one can secure.
I have measured the significance of interests in certain limited particulars, with very definite results, and shall, in this article, describe these results and the method by which they were obtained and by which any one can readily verify them.
The particular problems attacked all concerned the relative amount or relative intensity or relative strength of interests within the same individual. That is, "greater interest" will always mean the interest which was greater than the others possessed by the same individual. Little interest will mean little in comparison with the individual's other interests. The question, "To what extent is the strength of an interest from ten to fourteen prophetic of the strength which that interest will manifest in adult life?" will mean, "To what extent will it in adult life keep the same place in an order of the individual's interests which it had in the order which described his childish preferences?" Amounts or degrees of ability or capacity will similarly always mean relative amounts. Thus, to say that a person was, during high school, most interested in mathematics and most able at mathematics will mean that the person liked mathematics more than he did anything else, and did better at mathematics than he did at anything else. The statement will not imply anything about the degree of his interest or ability in comparison with other individuals.
The particular problems attacked are limited further to seven varieties of interests and the corresponding varieties of ability or capacity, namely, mathematics, history, literature, science, music, drawing, and other hand-work (this last being defined as "carpentering, sewing, ​gardening, cooking, carving, etc."). All comparisons or relations of interests and abilities are within this group, so that, for example, the statement that John Doe had interests in the high-school period distributed in the same order of strength as in the elementary-school period will mean that these seven interests had the same order in the two periods.
Such being the meanings of terms and the limitations of the field of inquiry I have measured:
1. The permanence of interests from the last three years of the elementary-school period to the junior year of college or professional school. 2. The correlation or correspondence between interests in a given subject and ability therein at the elementary-school period. 3. The same relation at the high-school period. 4. The same relation toward the end of the college or professional course. 5. The same relation on the whole (this will be explained later). 6. The correlation or correspondence between interest in a given subject at the end of the elementary-school period (during its last three years) and ability in that subject toward the end of the college or professional-school period.
The results to be here reported are for one hundred individuals, juniors in Barnard College, Columbia College and Teachers College. These results are corroborated by a similar but less minute study of two hundred other individuals.
The original measures are the judgments of the hundred individuals themselves concerning the order of their interests in mathematics, history, literature and the rest, at each of the three periods. Each individual reported in writing in response to the following instructions:
Experiment 34. (Table 1)
Consider your interests in the activities listed below during the last three years of your attendance at the elementary school. Mark (under El. Interest) with a 1 the activity which at that period was to you the most interesting of the seven listed. Mark the one that was next most interesting, 2; and so on.
Record similarly (under H. S. Interest) the order of interest for you during the high school period. Record similarly (under Col. Interest) the order of interest for you now.
Pay no attention at present to the spaces under ability.
Table 1
| | In Last Three Years of Elementary School | In Last Three Years of Elementary School | In High School | In High School | In College | In College |
| | El. Interest | El. Ability | H. S. Interest | H. S. Ability | C. Interest | C. Ability |
| Mathematics | | | | | | |
| History | | | | | | |
| Literature | | | | | | |
| Science | | | | | | |
| Music | | | | | | |
| Drawing | | | | | | |
| Other hand work | | | | | | |
Experiment 35
Consider your ability in each of the activities listed in Table 1, as it existed during the last three years of your attendance on the elementary school. Bank the activities from 1 to 7 according to your ability in each, marking that activity in which you had most ability 1. Record your ranks under the column headed El. Ability in Table 1. Record similarly (under H. S. Ability) the order of ability for you during the H. S. period. Record similarly (under C. Ability) the order of ability for you now.
We have then for each of the hundred a record such as is shown in the case of one of them in Table 2. These data are obviously subject to
Table 2
| | In Last Three Years of Elementary School | In Last Three Years of Elementary School | In High School | In High School | In College | In College |
| | El. Interest | El. Ability | H. S. Interest | H. S. Ability | C. Interest | C. Ability |
| Mathematics | 3 | 3 | 3 | 2 | 4 | 2 |
| History | 1 | 1 | 4 | 3 | 1 | 1 |
| Literature | 2 | 2 | 2 | 1 | 2 | 3 |
| Science | 4 | 4 | 1 | 4 | 3 | 4 |
| Music | 5 | 5 | 7 | 5 | 5 | 7 |
| Drawing | 6 | 6 | 5 | 7 | 6 | 5 |
| Other hand work | 7 | 7 | 6 | 6 | 7 | 6 |
certain errors of memory, prejudice, carelessness and the like, which will, later, be given due attention. It will be best to consider first what the meaning of the records would be, were each number a perfectly true statement of the relative strength of the interest or ability in question. Consider then this sample record as perfectly true and compute from it the differences between each subject's position for interest in the last three years of the elementary-school period (column 1) and for the high-school period (column 3).
​We have:
| Mathematics | 0 |
| History | 3 |
| Literature | 0 |
| Science | 3 |
| Music | 2 |
| Drawing | 1 |
| Other hand-work | 1 |
| Sum of the seven differences | 10 |
These facts are repeated in the first column of Table 3.
Table 3
| | I Difference Be- tween El. Interest Rank and H. S. Interest Rank | II Difference Be- tween El. Interest Rank and C. Interest Rank | III Difference Be- tween H. S. Inter- est Rank and C. Interest Rank |
| Mathematics | 0 | 1 | 1 |
| History | 3 | 0 | 3 |
| Literature | 0 | 0 | 0 |
| Science | 3 | 1 | 2 |
| Music | 2 | 0 | 2 |
| Drawing | 1 | 0 | 1 |
| Other hand-work | 1 | 0 | 1 |
| | 10 | 2 | 10 |
Computing the other differences as shown in the second and third column of Table 3, we have for this individual the means of answering question 1, concerning the permanence of interests. If the individual had remained unchanged in his interests from any one period to any other the appropriate seven differences of Table 3 would obviously have been all zeros and the sum of that column would have been zero. If, on the other hand, he had from one to another period, changed as completely as possible, the sum of the appropriate column of Table 3 would have been 24 (7-1, 6-2, 5-3, 4-4, 3-5, 2-6, 1-7 giving 24). If the individual's interests had been due to mere caprice, changing their relative strength at random, the sum of any column of Table 3 would approximate 16. For, if a 1 is equally likely to become a 1, 2, 3, 4, 5, 6 or 7, and so also of a 2, a 3, a 4, etc., the average result will be 16.
Any quantity below 16 as the sum of a column then means some permanence of interests in the individual in question, and the degree of permanence is measured by the divergence from 16 toward 0.
For the permanence from the elementary-school period to the junior ​year of college or professional school in my hundred individuals this figure is, on the average 9, three fifths of the individuals showing sums of from 6 to 12 for column 2 of Table 3. This average result of 9 may be expressed as a coefficient of correlation or correspondence, such as is in customary use to measure resemblances of various sorts. It is equivalent to a correlation of over.60. This means that a person's interests in the late elementary-school period resemble, in their order and relative strength, the constitution of interests which he will have eight years later to the extent of six tenths of perfect resemblance. For the coefficient of correlation is a magnitude running from ${\ce {-}}$ 1.0, which would be the coefficient if the sum of differences was 24, through 0, which would correspond to a sum of differences of 16, to ${\ce {+}}$ 1.0, which would correspond to a sum of differences of 0. A sum of differences of 8 means a resemblance greater than half of perfect resemblance, as the reader expert in the mathematics of probability will realize. The sums 12, 10, 8 and 6, in fact, mean coefficients of resemblance or correlation of +.38, +.55 +.71, and +.83, respectively.
The effect which the errors to which the original reports are subject would have in making this obtained degree of permanence too high or too low may now be considered. The chance errors—the mere failures of memory or carelessness in report or inability to distinguish slight differences in the interest of nearly equally interesting subjects—would make the obtained estimate too low. Their action would be to change the true sum of differences, whatever it was, toward 16, or the true coefficient of correlation toward zero. The effect of errors of prejudice, on the other hand, might have been toward so distorting memory and observation as to make the order given for interests in the two later periods more like the order given for the elementary-school period than was in truth the case. This would, of course, unduly raise the obtained estimate of permanence (that is, lower the sum of the differences). I do not believe that such tendencies to read present interests into the past and to leave the order reported for one period unchanged so far as possible, are very strong, there being a contrary tendency to remember and look for differences. On the whole, I should expect the effect of the large chance errors in lowering the estimate of permanence to nearly or quite counteract whatever balance of prejudice there may be in favor of similarity of interests or projection of present conditions into the past.
A correlation of .6 or .7 seems then to be approximately the true degree of resemblance between the relative degree of an interest in a child of from ten to fourteen and in the same person at twenty-one.
Consider now the difference between a subject's rank for interest and its rank for ability at the same period. Using the same sample record (Table 2) and assuming it to be a true record of the order of interests ​and computing from it the difference between each subject's position for interest in the elementary-school period (column 1) and its position for ability in the same period (column 2), we have:
| Mathematics | 0 |
| History | 0 |
| Literature | 0 |
| Science | 0 |
| Music | 0 |
| Drawing | 0 |
| Other hand work | 0 |
These facts are repeated in the first column of Table 4. Similar facts for this same individual, for the differences between the order for interest and the order for ability in the high-school period and in the college period are given in the second and third columns of Table 4.
Table 4
| | I Differences Between El. Interest and El. Ability | II Differences Between H. S. Interest and H. S. Ability | III Differences Between C. Interest and C. Ability |
| Mathematics | 0 | 1 | 2 |
| History | 0 | 1 | 0 |
| Literature | 0 | 1 | 1 |
| Science | 0 | 3 | 1 |
| Music | 0 | 2 | 2 |
| Drawing | 0 | 2 | 1 |
| Other hand-work | 0 | 0 | 1 |
If at any period an individual has greatest ability in the subject which is most interesting to him, next greatest ability in the next most interesting subject, and so on, the sum of the seven differences for that period will be zero. If the order of ability was as unlike as possible to the order of interest this sum would be 24, and if the relation between interest and ability was that of mere chance this sum would be 16. Any quantity below 16 as the sum of a column in Table 4 then means some positive relation or resemblance between the individual's degrees of interest and his degrees of ability.
For the hundred individuals studied this figure is on the average approximately 5, being practically the same for the elementary-school period, for the high-school period and for the college period. This average result may be expressed as a coefficient of correlation of .88. Nearly three fourths of the individuals show records between 2 and 8, inclusive—that is, correlations of from .70 to .98.
If, in the case of any individual, we add together the three ranks for each subject in interest at the three periods and do likewise for its ability-ranks, we have measures of the general order of the seven subjects ​for interest and for ability over the whole period from, say, the age of eleven to the age of twenty-one. Thus, in the sample chosen, the combined ranks give:
| | Sum of Ranks for Interest, All Three Periods | Sum of Ranks for Ability, All Three Periods |
| Mathematics | 10 | 7 |
| History | 6 | 5 |
| Literature | 6 | 6 |
| Science | 8 | 12 |
| Music | 17 | 17 |
| Drawing | 17 | 18 |
| Other hand-work | 20 | 19 |
Turning these into positions from 1 to 7, we have:
| | General Rank for Interest | General Rank for Ability |
| Mathematics | 4 | 3 |
| History | 11/2 | 1 |
| Literature | 11/2 | 2 |
| Science | 3 | 4 |
| Music | 51/2 | 5 |
| Drawing | 51/2 | 6 |
| Other hand-work | 7 | 7 |
The differences in the order are then 1, 1/2, 1/2, 1, 1/2, 1/2 and 0, their sum being 4.
I have made the calculation for each of the hundred individuals. On the average this sum of differences is approximately 412, and corresponds to a coefficient of correlation of .91. The individual whose interests follow his capacities least closely still shows a substantial resemblance (nearly .5). The correlation between an individual's order of subjects for interest and his order for ability is in fact one of the closest of any that are known. A person's relative interests are an extraordinarily accurate symptom of his relative capacities.
The effect which the errors to which the original reports are subject is on the whole probably to make this obtained degree of resemblance between interest and capacity too low. Errors due to accident, carelessness, and inability to distinguish or to remember slight differences in interest or in capacity, would make the sums of difference in the long run greater—and the degree of resemblance obtained, less—than the true facts, would have given. The only sort of error that could make the obtained resemblance greater than the true fact would be an error whereby either order was falsified to make it more like the other, notably, the possible tendency to rate oneself higher than one should for ability in a subject which one likes. On the whole, the resemblance ​between interest and ability may safely be placed at about .9 of perfect resemblance.
I have computed the resemblance between interest in the last three years of the elementary school and capacity in the college period as a partial measure of the extent to which early interest could be used as a symptom of adult capacity. The average for the hundred individuals is a coefficient of correlation or resemblance of .60.
I have also, for comparison with the last measurement and with the measurement of the resemblance of interest in the late elementary period to interest in the college period, computed the coefficient of correlation or resemblance between the order of the seven subjects for ability in the elementary and their order for ability in the college period, using the records from these same hundred individuals. The average resemblance obtained is six and a half tenths, or slightly closer than that for early and late interest.
These facts unanimously witness to the importance of early interests. They are shown to be far from fickle and evanescent. On the contrary, the order of interests at twenty shows six tenths of perfect resemblance to the order from eleven to fourteen, and has changed therefrom little more than the order of abilities has changed. It would indeed be hard to find any feature of a human being which was a much more permanent fact of his nature than his relative degrees of interest in different lines of thought and action.
Interests are also shown to be symptomatic, to a very great extent, of present and future capacity or ability. Either because one likes what he can do well, or because one gives zeal and effort to what he likes, or because interest and ability are both symptoms of some fundamental feature of the individual's original nature, or because of the combined action of all three of these factors, interest and ability are bound very closely together. The bond is so close that either may be used as a symptom for the other almost as well as for itself.
The importance of these facts for the whole field of practise with respect to early diagnosis, vocational guidance, the work of social secretaries, deans, advisers and others who direct students' choices of schools, studies and careers, is obvious. They should be taken account of in such practise until they are verified, or modified by data obtained by a better method: and such data should be soon collected. The better method is, of course, to get the measurements of relative interest and of relative ability, not from memory, but at the time; and not from individuals' reports alone, but by objective tests. Such an investigation iequires a repeated survey of each individual at three or more periods, say in 1912, 1915 and 1920, and demands skill and pertinacity in keeping track of the hundred or more children and arranging for the second and third series of reports and tests. I hope that some one of my readers will be moved to undertake it.
* ↑ Other hand work means carpentering, sewing, gardening, cooking, earring, etc.
* ↑   1 becoming 1, 2, 3, 4, 5, 6, 7 gives as differences 0, 1, 2, 3, 4, 5, 6; 2 becoming 1, 2, 3, 4, 5, 6, 7 gives as differences 1, 0, 1, 2, 3, 4, 5; 3 becoming 1, 2, 3, 4, 5, 6, 7 gives as differences 2, 1, 0, 1, 2, 3, 4. Continuing and dividing the sum of the 49 differences by 49 we get 2 2/7 for the average difference by mere chance shifting and 7 X 2 2/7 or 16, as the average sum of a column in Table 3 by mere chance shifting.