Individual Differences · The Science of Human Nature

INDIVIDUAL DIFFERENCES

=Physical Differences.= One never sees two people whose bodies are exactly alike. They differ in height or weight or color of the skin. They differ in the color of the hair or eyes, in the shape of the head, or in such details as size and shape of the ear, size and shape of the nose, chin, mouth, teeth, feet, hands, fingers, toes, nails, etc. The anatomist tells us that we differ internally just as we do externally. While the internal structure of one person has the same general plan as that of another, there being the same number of bones, muscles, organs, etc., there are always differences in detail. We are built on the same plan, _i.e._ we are made after a common type. We vary, above and below this type or central tendency.

Weight may be taken for illustration. If we should weigh the first thousand men we meet, we should find light men, heavy men, and men of medium weight. There would be few light men, few heavy men, but many men of medium weight. This fact is well shown in diagram by what is known as a curve of distribution or frequency surface, which is constructed as follows: Draw a base line A B, and on this line mark off equal distances to represent the various weights. At the left end put the number representing the lightest men and at the right the number representing the heaviest men; the other weights come in between in order. Then select a scale; we will say a millimeter in height above the base line represents one person of the weight represented on the base, and in drawing the upper part of the figure, A C B, we have but to measure up one millimeter for each person weighed, of the weight indicated below on the base.

[Illustration: FIGURE V--FREQUENCY SURFACE--WEIGHT The solid line represents men, the broken line, women.]

A study of this frequency surface shows a tendency for people to be grouped about the central tendency or average. There are many people of average weight or nearly so, but few people who deviate widely from the average weight. If we measure people with reference to any other physical characteristic, or any mental characteristic, we get a similar result, we find them grouped about an average or central tendency.

=Mental Differences.= Just as we differ physically, so also we differ mentally, and in the various aspects of our behavior. The accompanying diagram (Free Association) shows the distribution of a large number of men and women with respect to the speed of their flow of ideas. When men and women are measured with respect to any mental function, a similar distribution is found.

[Illustration: FIGURE VI--FREQUENCY SURFACE--FREE ASSOCIATION Solid line, men; broken line, women. The numbers below the base represent the number of words written in the Free Association test, and the numbers at the left represent the number of people making the respective scores.]

An interesting question is whether our mental differences have any relation or connection with one another. If one mental characteristic is of high order, are all the others of high order also? Does a good memory indicate a high order of attention, of association, of imagination, of learning capacity? Experiments show that mental characteristics have at least some degree of independence. But the rule is that they generally go together, a high order of ability in one mental function indicating a high order of ability in at least some others, and a low order of ability in one function indicating a low order in other functions.

However, it seems that abilities that are very much specialized, such as musical ability, artistic ability, etc., may exist in high order while other mental functions may be only mediocre. It is a common thing for a musical person to be of rather poor ability otherwise. To the extent that special abilities require specialized differences in the structure of brain, nervous system, or sense organ, they can exist in some degree of independence of other functions. Musical ability to some extent does require some such differences and may therefore be found either with a high or a low degree of ability in other characteristics.

It is doubtless true that at maturity the unequal power of mental functions in the same person may be partly due to the fact that one function has been exercised and others neglected. A person having very strong musical tendencies is likely to have such a great interest in music that he will think other activities are not worth while, and will consequently neglect these other activities. It will therefore turn out that at maturity the great differences in mental functions in such a person are in part due to exercise of one function and neglect of others. But there can be no doubt that in many cases there are large original, inherited differences, the individual being poor in one aspect of mind and good in others. Feeble-minded people are usually poor in all important aspects of mind. However, one sometimes finds a feeble-minded person having musical or artistic ability, and often such a person has a good rote memory, sometimes a good verbal memory. However, the so-called higher mental functions--logical memory, controlled association, and constructive imagination--are all poor in a feeble-minded person.

Each mental function may be looked upon as in some measure independent; each is found existing in people in varying degrees from zero ability up to what might be called genius ability. The frequency curves in Fig. VI show this. Take rote memory for example. Idiots are found with practically zero ability in rote memory. At the other extreme, we find mathematical prodigies who, after watching a long freight train pass and noting the numbers of the cars, can repeat correctly the number of each car. Rote memory abilities can be found representing every step between these two extremes. This principle of distribution holds true in the case of all mental functions. We find persons practically without them, and others possessing them in the highest order, but most people are grouped about the average ability.

=Detecting Mental Differences.= It has already been said that mind has many different aspects and that people differ with respect to these aspects. Now let us ask how we can measure the degree of development of these aspects or functions of mind. We measure them just as we measured muscular speed as described in the first chapter. Each mental function means ability to do something--to learn, to remember, to form images, to reason, etc. To measure these different capacities or functions we have but to require that the person under consideration _do_ something, as learn, remember, etc., and measure how well and how fast he does it, just as we would measure how far he can jump, how fast he can run, etc.

In such measurements, the question of practice is always involved. If we measure running ability, we find that some are in practice while others are not. Those in practice can run at very nearly their ultimate capacity. Those who are not in practice can be trained to run much faster than they do. To get a true measure of running capacity, we should practice the persons to be measured till each runs up to the limit of his capacity, and then measure each one's speed. The same thing is true, to some extent, when we come to measure mental functions proper. However, the life that children live gives exercise to all fundamental functions of the mind, and unless some of the children tested have had experience which would tend to develop some mental functions in a special way, tests of the various aspects of learning capacity, memory, association, imagination, etc., are a fairly good measure of original, inherited tendencies.

Of course, it must be admitted that there are measurable differences in the influence of environment on children, and when these differences are extreme, no doubt the influence is shown in the development of the child's mind. A child reared in a home where all the influences favor its mental development, ought to show a measurable difference in such development when compared with a child reared in a home where all the influences are unfavorable. It is difficult to know to what extent this is true, for the hereditary and environmental influences are usually in harmony, the child of good hereditary stock having good environmental influences, and vice versa. When this is not the case, _i.e._ when a child of good stock is reared under poor environmental influences, or when a child of poor stock is reared under good influences, the results seem to show that the differences in environment have little effect on mental development, as far as the fundamental functions are concerned, except in the most extreme cases.

Each mental function is capable of some development. It can be brought up to the limit of its possibilities. But recent experiments indicate that such development is not very great in the case of the elementary, fundamental functions. Training, however, has a much greater effect on complex mental activities that involve several functions. Rote memory is rather simple; it cannot be much affected by training. The memory for ideas is more complex; it can be considerably affected by training. The original and fundamental functions of the mind depend upon the nature of the nervous system which is bequeathed to us by heredity. This cannot be much changed. However, training has considerable effect on the coördinations and combinations of mental functions. Therefore, the more complex the mental activities which we are testing, the more likely they are to have been affected by differences in experience and training.

If we should designate the logical memory capacity of one person by 10, and that of another by 15, by practice we might bring the first up to 15 and the second to 22½, but we could not equalize them. We could never make the memory of the one equal to that of the other. In an extreme case, we might find one child whose experience had been such that his logical memory was working up to the limit of its capacity, while the other had had little practice in logical memory and was therefore far below his real capacity. In such a case, a test would not show the native difference, it would show only the present difference in functioning capacity.

Fairly adequate tests for the most important mental functions have been worked out. A series of group tests with directions and norms follow. The members of the class can use these tests in studying the individual differences in other people. The teacher will find other tests in the author's _Examination of School Children_, and in Whipple's _Manual of Mental and Physical Tests_.

=MENTAL TESTS=

GENERAL DIRECTIONS

The results of the mental tests in the school will be worse than useless unless the tests are given with the greatest care and scientific precision. Every test should be most carefully explained to the children so that they will know _exactly_ what they are to do. The matter must be so presented to them that they will put forth _all possible_ effort. They must take the tests seriously. Great care must be taken to see that there is no cheating. The work of each child should be his own work. In those tests in which time is an important element, the time must be _carefully kept_, with a stop watch if one is available. The papers should be distributed for the tests and turned face downward on the pupil's desk. The pupil, when all are ready to begin, should take the paper in his hand and at the signal "begin" turn it over and begin work, and when the signal "stop" is given, should quit work instantly and turn the paper over. Before the work begins, the necessary information should be placed on each paper. This information should be the pupil's name, age, grade, sex, and school. This should be on every paper. When the test is over the papers should be immediately collected.

LOGICAL MEMORY

=Object.= The purpose of this test is to determine the pupil's facility in remembering and reproducing ideas. A pupil's standing in the test may serve as an indication of his ability to remember the subject matter of the school studies.

[Illustration: FIGURE VII--LOGICAL MEMORY "WILLIE JONES"]

=Method.= The procedure in this test is for the teacher to read slowly and distinctly the story to be reproduced. Immediately after the reading the pupils are to write down all of the story that they can recall. They must not begin to write till _after_ the reading. Ten minutes should be allowed for the reproduction. This is ample time, and each pupil should be told to use the whole time in working on his reproduction. At the end of ten minutes, collect the papers. Care should be taken to see that each pupil does his own work, that there is no copying. Before reading the story, the teacher should give the following instructions:

I shall read to you a story entitled "Willie Jones and His Dog" (or "A Farmer's Son," or "A Costly Temper," as the case may be). After I have read the story you are to write down all you can remember of it. You are not to use the exact words that I read unless you wish. You are to use your own words. Try to recall as much as possible and write all you recall. Try to get all the details, not merely the main facts.

=Material.= For grades three, four, and five, use "Willie Jones and His Dog"; for grades six, seven, and eight, use "A Farmer's Son"; for the high school, use "A Costly Temper." The norms for the latter are based on eighth grade and high school pupils.

* * * * *

WILLIE JONES AND HIS DOG

A FARMER'S SON

A COSTLY TEMPER

* * * * *

[Illustration: FIGURE VIII--LOGICAL MEMORY--"A FARMER'S SON"]

=The Results.= The material for the test is divided into units as indicated by the vertical lines. The pupil's written reproduction should be compared unit by unit with the story as printed, and given one credit for each unit adequately reproduced. The norms for the three tests are shown in the accompanying Figures VII, VIII, and IX. In these and all the graphs which follow, the actual ages are shown in the first horizontal column. The norms for girls appear in the second horizontal column, the norms for boys in the column at the bottom. By the _norm_ for an age is meant the average performance of all the pupils of that age examined. Age ten applies to those pupils who have passed their tenth birthday and have not reached their eleventh birthday, and the other ages are to be similarly interpreted. The vertical lines in the graphs indicate birthdays and the scores written on these lines indicate ability at these exact ages. The column marked ten, for example, includes all the children that are over ten and not yet eleven. The graphs show the development from age to age. In general, it will be noticed, there is an improvement of memory with age, but in the high school, in the "Costly Temper" test, there is a decline. This may not indicate a real decline in ability to remember ideas, but a change in attitude. The high school pupil probably acquires a habit of remembering only significant facts. His memory is selective, while in the earlier ages, the memory may be more parrot-like, one idea being reproduced with about as much fidelity as another. This statement is made not as a _fact_, but as a _probable_ explanation.

ROTE MEMORY

[Illustration: FIGURE IX--LOGICAL MEMORY--"A COSTLY TEMPER"]

=Object.= The object of the rote memory tests is to determine the pupil's memory span for unrelated impressions--words that have no logical relations with one another. Much school work makes demands upon this ability. Therefore, the tests are of importance.

=Method.= There are two lists of words, _concrete_ and _abstract_, with six groups in each list. The list of concrete words should be given first, then the abstract. The procedure is to pronounce the first group, _cat_, _tree_, _coat_, and then pause for the pupils to write these three words. Then pronounce the next group, _mule_, _bird_, _cart_, _glass_, and pause for the reproduction, and so on through the list.

[Illustration: FIGURE X--CONCRETE ROTE MEMORY]

Give the following instructions:

We wish to see how well you can remember words. I shall pronounce first a group of three words. _After_ I have pronounced them, you are to write them down. I shall then pronounce a group of four words, then one of five words, and so continue with a longer group each time. You must pay very close attention for I shall pronounce a group but once. You are not required to write the words in their order, but just as you recall them.

=Material.= The words for the test are given in the following lists:

_Concrete_ _Abstract_

1. cat, tree, coat 1. good, black, fast 2. mule, bird, cart, glass 2. clean, tall, round, hot 3. star, horse, dress, fence, man 3. long, wet, fierce, white, cold 4. fish, sun, head, door, shoe, 4. deep, soft, quick, dark, great, block dead 5. train, mill, box, desk, oil, 5. sad, strong, hard, bright, pup, bill fine, glad, plain 6. floor, car, pipe, bridge, hand, 6. sharp, late, sour, wide, rough, dirt, cow, crank thick, red, tight

[Illustration: FIGURE XI--ABSTRACT ROTE MEMORY]

=Results.= The papers are graded by determining the number of concrete words and the number of abstract words that are reproduced. No account is taken of whether the words are in the right position or not. A perfect score in each test would therefore be thirty-three. The norms are shown in Figures X and XI.

THE SUBSTITUTION TEST

=Object.= This test determines one's ability to build up new associations. It is a test of quickness of learning.

=Method.= The substitution test-sheets are distributed to the pupils and turned face down on the desks. The teacher gives the following instructions:

We wish to see how fast you can learn. At the top of the sheet which has been distributed to you there is a key. In nine circles are written the nine digits and for each digit there is written a letter which is to be used instead of the digit. Below the key are two columns of numbers; each number contains five digits. In the five squares which follow the number you are to write the letters which correspond to the digits. Work as fast as you can and fill as many of the squares as you can without making mistakes. When I say "stop," quit work instantly and turn the paper over.

Before beginning the test the teacher should explain on the blackboard the exact nature of the test. This can be done by using other letters instead of those used in the key. Make sure that the pupils understand what they are to do. Allow _eight_ minutes in grades three, four, and five, and _five_ minutes above the fifth grade.

=Material.= For material, use the substitution test-sheets. This and the other test material can be obtained from the University of Missouri, Extension Division.

=Results.= In grading the work, count each square correctly filled in as one point, and reduce the score to speed per minute by dividing by eight in grades three, four, and five, and by five in the grades above.

The norms are shown in Figure XII.

[Illustration: FIGURE XII--SUBSTITUTION TEST]

FREE ASSOCIATION

=Object.= This test determines the speed of the free flow of ideas. The result of the test is a criterion of the quickness of the flow of ideas when no restriction or limitation is put on this flow.

=Method.= The procedure in this test is to give the pupils a word, and tell them to write this word down and all the other words that come into their minds. Make it clear to them that they are to write whatever word comes to mind, whether it has any relation to the word that is given them or not. Start them with the word "cloud." Give the following instructions:

I wish to see how many words you can think of and write down in three minutes. I shall name a word, you may write it down and then all the other words that come into your minds. Do not write sentences, merely the words that come into your minds. Work as fast as you can.

[Illustration: FIGURE XIII--FREE ASSOCIATION TEST]

=Results.= Score the work by counting the number of words that have been written. The norms are shown in Figure XIII.

OPPOSITES

=Object.= This is a test of controlled association. It tests one aspect of the association of ideas. All thinking is a matter of association of ideas. Reasoning is controlled association. The test may therefore be taken as a measure of speed in reasoning.

[Illustration: FIGURE XIV--OPPOSITES TEST--LISTS I AND II]

=Method.= Distribute the lists of opposites to the pupils and turn them face down on the desks. Use List One in grades three, four, and five, and List Two in grades above. Allow two minutes in grades three, four, and five and one minute in grades above. Give the following instructions:

On the sheets that have been distributed to you are fifty words. After each word you are to write a word that has the opposite meaning. For example, if one word were "far," you could write "near." Work as fast as you can, and when I say "stop" quit work instantly and turn your paper over.

=Results.= The score is the number of opposites correctly written. The norms are shown in Figure XIV.

OPPOSITES--LIST NO. 1

1. good 18. up 35. before 2. big 19. thick 36. winter 3. rich 20. quick 37. ripe 4. out 21. pretty 38. night 5. sick 22. heavy 39. open 6. hot 23. late 40. first 7. long 24. wrong 41. over 8. wet 25. smooth 42. love 9. yes 26. strong 43. come 10. high 27. dark 44. east 11. hard 28. dead 45. top 12. sweet 29. wide 46. wise 13. clean 30. empty 47. front 14. sharp 31. above 48. girl 15. fast 32. north 49. sad 16. black 33. laugh 50. fat 17. old 34. man

OPPOSITES--LIST NO. 2

1. strong 18. strange 35. fine 2. deep 19. wrong 36. plain 3. lazy 20. quickly 37. sharp 4. seldom 21. black 38. late 5. thin 22. good 39. sour 6. soft 23. fast 40. wide 7. many 24. clean 41. drunk 8. valuable 25. tall 42. tight 9. gloomy 26. hot 43. empty 10. rude 27. long 44. sick 11. dark 28. wet 45. friend 12. rough 29. fierce 46. above 13. pretty 30. great 47. loud 14. high 31. dead 48. war 15. foolish 32. cloudy 49. in 16. present 33. hard 50. yes 17. glad 34. bright

THE WORD-BUILDING TEST

=Object.= This is a test of a certain type of inventiveness, namely linguistic invention. Specifically, it tests the pupil's ability to construct words using certain prescribed letters.

[Illustration: FIGURE XV--WORD-BUILDING TEST]

=Method.= The pupils are given the letters, _a_, _e_, _o_, _m_, _n_, _r_, and told to make as many words as possible using only these letters. Give the following instructions:

I wish to see how many words you can make in five minutes, using only the letters which I give you. The words must be real English words. You must use only the letters which I give you and must not use the same letter more than once in the same word. You do not, of course, have to use all the letters in the same word. A word may contain one or more letters up to six.

=Material.= The pupils need only sheets of blank paper.

=Results.= The score is the number of words that do not violate the rules of the test as given in the instructions. The norms are shown in Figure XV.

THE COMPLETION TEST

=Object.= This is, to some extent, a test of reasoning capacity. Of course, it is only one particular aspect of reasoning. The pupil is given a story that has certain words omitted. He must read the story, see what it is trying to say, and determine what words, put into the blanks, will make the correct sense. The meaning of the word written in a particular blank must not only make the sentence read sensibly but must fit into the story _as a whole_. Filling in the blanks in this way demands considerable thought.

=Method.= Distribute the test-sheets and turn them face down on the desks. Allow ten minutes in all the tests. Give the following instructions:

On the sheets which have been distributed is printed a story which has certain words omitted. You are to put in the blanks the words that are omitted. The words which you write in must give the proper meaning so that the story reads correctly. Each word filled in must not only give the proper meaning to the sentence but to the story as a whole.

=Material.= Use the completion test-sheets, "Joe and the Fourth of July," for grades three, four, and five; "The Trout" for grades, six, seven, and eight; and "Dr. Goldsmith's Medicine" for the high school.

=Results.= In scoring the papers, allow one credit for each blank correctly filled. The norms are shown in Figures XVI, XVII, and XVIII. It will be noticed that the boys excel in the "Trout" story. This is doubtless because the story is better suited to them on the ground of their experience and interest.

[Illustration: FIGURE XVI--COMPLETION TEST--"JOE AND THE FOURTH OF JULY"]

* * * * *

JOE AND THE FOURTH OF JULY

Joe {ran}[6] errands for {his} mother and {took} care of the {baby} until by the Fourth of July his penny {grew} to be a dime. The day before the Fourth, he {went} down town all by {himself} to get his fire {works}. There were so {many} kinds he hardly knew which to {buy}. The clerk knew that it takes a {long} time to decide, for he had been a {boy} himself not very {long} ago. So he helped Joe to {select} the very best kinds. "When are you going to {fire} them off?" asked the clerk. "I will fire {them} very {early} to-morrow," said the boy. So that night Joe set the {alarm} clock, and the next {morning} got up {early} to fire his firecrackers.

[6] The italicized words and letters are left blank in the test sheets.

THE TROUT

The trout is a fine fish. Once a big trout {lived} in a pool {close} by a spring. He used to {stay} under the bank with {only} his head showing. His wide-open {eyes} shone like jewels. I tried to {catch} him. I would {creep} up to the {edge} of the pool {where} I could see his {bright} eyes looking up.

I {caught} a grasshopper and {threw} it over {to} him. Then there was a {splash} in the water and the grasshopper {was gone}. I {did} this {two} or three times. Each time I {saw} the rush and splash and saw the bait had been {taken}.

So I put the sa{me} bait on my {hook} and {threw} it over into the {water}. But {all} was silent. The fish was an {old} one and had {grown} very wise. I did this {day} after day with the same luck. The trout {knew} there was a {hook} hidden in the bait.

[Illustration: FIGURE XVII--COMPLETION TEST--"THE TROUT"]

DOCTOR GOLDSMITH'S MEDICINE

This {is} a story of good medicine. Most medicine is {bad} to {take}, but this was so good {that} the sick man {wished} for more.

{One} day a poor woman {went} to Doctor Goldsmith and {asked} him to {go} to see her {sick} husband. "He {is} very sick," she said, "and I {can} not {get} him to eat anything."

{So} Doctor Goldsmith {went} to {see} him. The doctor {saw} at once that the {reason} why the man {could} not eat was {because} he was {so} poor that he had {not} been {able} to buy good food.

Then he {said} to the woman, "{Come} to my house this evening and I will {give you} some {medicine} for your {husband}."

The woman {went} in the evening and the {doctor} gave {her} a small paper box tied {up} tight. "{It} is very heavy," {she} said. "May I {see} what it looks {like}?" "{No}," said the doctor, "{wait} until you get {home}." When she {got} home, and she and {her} husband {opened} the box so that he {could} take the first {dose} of medicine,--what do you think they {saw}? The box was {filled} with silver {money}. {This} was the {good} doctor's medicine.

* * * * *

=Importance of Mental Differences.= (1) _In school work._ One of the important results that come from a knowledge of the mental differences in children is that we are able to classify them better. When a child enters school he should be allowed to proceed through the course as fast as his development warrants. Some children can do an eight-year course in six years; others require ten years; still others can never do it. The great majority, of course, can do it in eight years.

[Illustration: FIGURE XVIII--COMPLETION TEST--"DR. GOLDSMITH'S MEDICINE"]

Norms for adults, as obtained from university students, are:

TEST MEN WOMEN Substitution Test 29.1 32.2 Rote Memory, Concrete 28.5 28.6 Rote Memory, Abstract 28.4 27.9 Free Association 51.5 49.3 Completion, _Dr. Goldsmith's Medicine_ 48.1 49.0 Word Building 20.5 20.1 Logical Memory, _Costly Temper_ 64.0 69.6

[Illustration: FIGURE XIX--FREQUENCY SURFACES--COMPARING FOURTH GRADE WITH HIGH SCHOOL

The numbers along the base represent mental age; those at the left, the number of pupils of the respective ages.]

It may be thought that a child's success in school branches is a sufficient measure of his ability and that no special mental measurements are needed. This is a mistake. Many factors contribute to success in school work. Ability is only one of these factors, and should be specially and independently determined by suitable tests. Children may fail in school branches because of being poorly started or started at the wrong time, because of poor teaching, sickness, moving from one school to another, etc. On the other hand, children of poor ability may succeed at school because of much help at home. Therefore special mental tests will help in determining to what extent original mental ability is a factor in the success or failure of the different pupils.

As far as possible, the children of the same grade should have about the same ability; but such is seldom the case. In a recent psychological study of a school system, the author found wide differences in ability in the same grade. The distribution of abilities found in the fourth grade and in the high school are shown in Figure XIX. It will be seen that in the fourth grade pupils are found with ability equal to that of some in the high school. Of course to some extent such a condition is unavoidable, for a pupil must establish certain habits and acquire certain knowledge before passing from one grade to another. However, much of the wide variation in ability now found in the same grade of a school could be avoided if the teacher had accurate knowledge of the pupils' abilities. When a teacher learns that a child who is doing poorly in school really has ability, she is often able to get from that pupil the work of which he is capable. It has been demonstrated by experience that accurate measures of children's abilities are a great help in gradation and classification.

A knowledge of mental differences is also an aid in the actual teaching of the children. The instance mentioned at the close of the last paragraph is an example. A knowledge of the differences among the mental functions of the same pupil is especially helpful. It has been pointed out that the different mental functions in the same pupil are sometimes unequally developed. Sometimes considerable differences exist in the same pupil with respect to learning capacity, the different aspects of memory, association, imagination, and attention. When a teacher knows of these differences, she can better direct the work of the pupils.

For example, if a pupil have a very poor memory, the teacher can help him by aiding him to secure the advantage that comes from close and concentrated attention, frequent repetitions, logical organization, etc. On the other hand, she can help the brilliant student by preventing him from being satisfied with hastily secured, superficial knowledge, and by encouraging him to make proper use of his unusual powers in going deeper and more extensively into the school subjects than is possible for the ordinary student. In many ways a teacher can be helpful to her pupils if she has an accurate knowledge of their mental abilities.

(2) _In life occupations._ Extreme variations in ability should certainly be considered in choosing one's life work. Only persons of the highest ability should go into science, law, medicine, or teaching. Many occupations demand special kinds of ability, special types of reaction, of attention, imagination, etc. For example, the operation of a telephone exchange demands a person of quick and steady reaction. The work of a motorman on a street car demands a person having the broad type of attention, the type of attention that enables one to keep in mind many details at the same time. Scientific work demands the type of concentrated attention. As far as it is possible, occupations demanding special types of ability should be filled by people possessing these abilities. It is best for all concerned if each person is doing what he can do best. It is true that many occupations do not call for special types of ability. And therefore, as far as ability is concerned, a person could do as well in one of these occupations as in another. The time will sometime come when we shall know the special abilities demanded by the different occupations and professions, and by suitable tests shall be able to determine what people possess the required qualifications.

The schools should always be on the lookout for unusual ability. Children that are far superior to others of the same age should be allowed to advance as fast as their superior ability makes possible, and should be held up to a high order of work. Such superior people should be, as far as possible, in the same classes, so that they can the more easily be given the kind and amount of work that they need. The schools should find the children of unusual special ability, such as ability in drawing, painting, singing, playing musical instruments, mechanical invention, etc. Some provision should be made for the proper development and training of these unusual abilities. Society cannot afford to lose any spark of genius wherever found. Moreover, the individual will be happier if developed and trained along the line of his special ability.

=Subnormal Children.= A small percentage of children are of such low mentality that they cannot do the ordinary school work. As soon as such children can be picked out with certainty, they should be taken out of the regular classes and put into special classes. It is a mistake to try to get them to do the regular school work. They cannot do it, and they only waste the teacher's time and usually give her much trouble. Besides, they waste their own time; for while they cannot do the ordinary school work, they can do other things, perhaps work of a manual nature. The education of such people should, therefore, be in the direction of simple manual occupations.

For detecting such children, in addition to the tests given above, elaborate tests for individual examination have been devised. The most widely used is a series known as the Binet-Simon tests. A special group of tests is provided for the children of each age. If a child can pass the tests for his age, he is considered normal. If he can pass only the tests three years or more below his age, he is usually considered subnormal. But a child's fate should not depend solely upon any number or any kind of tests. We should always give the child a trial and see what he is able to achieve. This trial should cover as many months or years as are necessary to determine beyond doubt the child's mental status.

SUMMARY. Just as we differ in the various aspects of body, so also we differ in the various aspects of mind. These differences can be measured by tests. A knowledge of these differences should aid us in grading, classifying, and teaching children, as well as in the selection of occupation and professions for them. Mental traits have some degree of independence; as a result a high degree of one trait may be found with low degree of some others.

CLASS EXERCISES

1. Many of the tests and experiments already described should have shown many of the individual differences of the members of the class. The teacher will find in the author's _Examination of School Children_ a series of group tests with norms which can be used for a further study of individual differences.

2. The tapping experiment described in the first chapter can now be repeated and the results taken as a measure of reaction time.

3. You should now have available the records of all the tests and experiments so far given that show individual differences. Make out a table showing the rank of each student in the various tests. Compute the average rank of each student for all the tests. This average rank may be taken as a measure of the intelligence of the students, as far as such can be determined by the tests used. Correlate this ranking with standing in the high school classes. It will give a positive correlation, not perfect, however. Why not? If your measures of intelligence were absolutely correct, you still would not get a perfect correlation with high school standing. Why not?

4. If you had a correct measure of intelligence of 100 mature people in your city, selected at random, would this measure give you an exact measure of their success in life? Give the reason for your answer.

5. Of all the tests and experiments previously described in this book, which gives the best indication of success in high school?

6. If the class in psychology is a large one, a graph should be prepared showing the distribution of abilities in the class. For this purpose, you will have to use the absolute measures instead of ranks. Find the average for each test used. Make these averages all the same by multiplying the low ones and dividing the high ones. Then all the grades of each student can be added. This will give each test the same weight in the average. The use of a slide rule will make this transference to a new average very easy. A more accurate method for this computation is described in the author's _Examination of School Children_, p. 65.

The students should make a study of individual differences and the distribution of ability in some grade below the high school. The tests described in this chapter can be used for that purpose.

7. Is it a good thing for high school students to find out how they compare with others in their various mental functions? If you have poor ability, is it a good thing for you to find it out? If the teacher and students think best, the results of all the various tests need not be made known except to the persons concerned. The data can be used in the various computations without the students' knowing whose measures they are.

8. To what extent is ability a factor in life? You find people of only ordinary ability succeeding and brilliant people failing. Why is this?

9. None of the tests so far used measures ideals or perseverance and persistence. These are important factors in life, and there is no very adequate measure for any of them. The students might plan some experiments to test physical and mental persistence and endurance. The tapping experiment, for example, might be continued for an hour and the records kept for each minute. Then from these records a graph could be plotted showing the course of efficiency for the hour. Mental adding or multiplying might be kept up continuously for several hours and the results studied as above.

10. We have said that ideals and persistence are important factors in life. Are they inherited or acquired?

11. Do you find it to be the rule or the exception for a person standing high in one mental function to stand high in the others also?

12. Make a complete outline of the chapter.

REFERENCES FOR CLASS READING

MÜNSTERBERG: _Psychology, General and Applied_. Chapter XVI.

PYLE: _The Examination of School Children_.

PYLE: _The Outlines of Educational Psychology_. Chapter XVII.

TITCHENER: _A Beginner's Psychology_, pp. 309-311.