RJ 499 073 Journal of Psycho- H Asthenics Monograph Supplements Vol. 1, No. 2 June, 1915 Qualitative Differences Be- tween Levels of Intelligence in Feeble-Minded Children By Louise Ellison Ordahl, Ph. D. and George Ordahl, Ph. D. Published by Minn. Minded and Colony for Epilf. Faribault VOL. 1, No. 2 JUNE, 1915 Qualitative Differences Between Levels L- of Intelligence in Feeble-Minded Children , Louise Ellison Ordahl, Ph. D. and George Ordahl, Ph. D. VV Published by Minnesota School for Feeble- Minded and Colony for Epileptics, Faribault Press of Minnesota School for Feeble-Minded and Colony for Epileptics, Faribault. QUALITATIVE DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE IN FEEBLE-MINDED CHILDREN BY LOUISE ELLISON ORDAHL, Ph. D., and GEORGE ORDAHL, Ph. D. This study was undertaken at Faribault, Minnesota, in the psychological laboratory of the Minnesota School for Feeble- Minded and Colony for Epileptics. Work was begun June 6, 1914, and experiments were abruptly terminated October 26, 1914. The problem was suggested by Dr. F. Kuhlmann, Director of Research, who also rendered the authors valuable assistance in planning and arranging experiments. The Binet-Simon scale is a means of measuring degrees of general intelligence, but it does not specifically reveal the quali- tative differences upon which the various levels of intelligence depend. Groups of children, both normal and feeble-minded, may be graded into different levels of intelligence with a considerable degree of accuracy. But the psychological qualities character- istic of each group, and the consequent qualitative differences between each level has not yet been determined. In a general way it is quite apparent that the higher grades differ widely from the lower grades and it is quite possible to detect a considerable difference in the behavior of a group of children who are, for example, mentally six years old and another group whose mentality is seven years, but just what this differ- ence may be psychologically is not apparent. It has therefore seemed worth while to attempt a series of experiments calculated to reveal a psychological difference between the subjects doing the experiments. Accordingly this problem was undertaken. For the purpose of this study it would be best to attempt experiments on the simple mental processes, and in the field al- ready laid out by normal adult and child psychology, and to se- lect experiments for which norms are already established and which at the same time seem likely to yield results with this class 4 ORDAHL of people. Unfortunately very few exist which are at the same time applicable to the feeble-minded. The authors attempted to devise experiments which should test the psychological processes comprehended within the following rubrics : Sensory discrimin- ations, attention, memory, imagination, judgment, and reason. The individual experiments are designated as follows. 1. Strength of grip, dynamometer. 2. Judgment of movement. 3. Simple reaction to sound. 4. Tapping tests. 5. Attention span. 6. Discrimination of grays. 7. Judgment of forms, two dimensions. 8. Judgment of form. 9. Judgment of size. 10. Judgment of form, three dimensions. 11. Memory for geometrical forms. 12. Modified typewriting. 13. Ink blot test. 14. Drawing designs inverted. 15. Comprehension of complex directions. Thirty cases of typical feeble-minded "children" were se- lected, ranging between the chronological ages of fifteen and thirty-five. If it was found that a case was suffering from any special defect such as faulty vision, it was discarded and other cases tried. However, all defects, if of a minor degree, could not thus be eliminated since a case might be well along in the ex- periment 'before the defect 'became apparent. No cases were taken whose chronological ages were under fifteen. A child under this age with a mentality of ten is possibly quite different from one of the same mentality but chronolog- ically older. If a child is fifteen and grades ten or lower in men- tality he is well possessed of the feeble-minded traits and com- pares favorably with one of the same mental level but chron- ologically twenty or thirty-five. If, however, the chronological age is greater than thirty-five there is possibility of deterioration DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 5 having set in. For this reason our cases were limited to the chronological ages of fifteen to thirty-five. The cases were taken from three groups of children, whose mental ages were six, eight, and ten, as determined by the Binet- Simon scale. Ten cases were selected from each of these three mental ages, five girls and five boys, thus making an equal num- ber from each sex, a total of fifteen boys and fifteen girls. Sub- jects were taken who had not more than six months previous to the experiments tested within two-fifths of a year of the men- tal age. The average chronological and mental ages for each group were as follows. Chronological Mental By Groups Age Age Mental six 20.5 6.26 Mental eight 22.9 8.20 Mental ten 19-5 IO - 10 Chronological Mental By Sex Age Age Mental six girls 21 0.3 Mental six boys 20 6.2 Mental eight girls 22.5 8.2 Mental eight boys 23.4 Mental ten girls 21 9.9 Mental ten boys i?-3 iai6 The chronological ages for the different groups do not differ greatly. The Ten group has the lowest chronological average which may be in its favor. However, it cannot be much since the difference is but one year less than the Six group, and 3.4 years less than the Eight group. Whatever advantage this may give the Tens over the other groups is offset by the lower aver- age mental age which is .1 year less than for the Bight group, and .16 less than for the Six group. The Tens are placed at a further disadvantage by the fact that the girls of this group average slightly below ten years mentally, and two have the mental age of 9 3-5. In each of the other groups no individual was below the mental age for the group. The Tens are at a further disadvantage from the fact that two of its members scored lower than the Eights in many of the tests. This was due 6 ORDAHL in one case to a peculiar disposition which prevented the subject putting forth proper effort, and in the second case to a peculiar- ity of vision, and a deficiency in the general physical tonus. The Eights as a group 'have an advantage of the Tens in two ways, first, a slightly higher mental average, and second, there were two of its members who in many of the tests stood above the highest Tens. These facts should be born in mind in reading the various tables throughout the following pages. The figures are given as different groups scored, but for actual group differences the Tens should be slightly higher and the Eights slightly lower in every case, thus making the differences between the groups Eight and Ten greater than is actually shown by the tables. Throughout this study the terms Six, Eight and Ten, when capitalized, refer to, or are abbreviations for mental age six, men- tal age eight and mental age ten. The number of cases in each experiment is uniformly thirty, and is therefore not recorded in the tables. Experiment i. Strength of Grip. Each subject was tested for strength of grip in right and left hand. Three trials were given on each of three successive days. Smedley's Improved Dynamometer was used and directions fol- lowed as given in Whipple's Manual of Mental and Physical Tests, Vol. I, page 100. The test was given in the presence of two others of the group. The subject was handed the dynamometer after it had been fitted to his hands, with the following remarks : "John, here, has pulled most one hundred pounds on this dyna- mometer. Let us see what you can do." This was usually suf- ficient stimulus to call forth considerable effort, but it is still questionable if the results record the full capacity of the sub- jects, especially with the lower grades who did not seem to dis- tinguish between grimaces, contortions, and real muscular ac- tion. Several trials were made on a subject with no others pres- ent. The great variability in the results led the author to discard this method since the results varied so much with different trials that it was evident only a small effort was being exerted. With the method used the variations were only a few pounds. The average in Kg. for the groups were as follows. TABLE I Right band bix 25.2 Eight Ten . 29.4 29.7 Left band 22.5 26.5 29.2 TABLE II Girls Six . . Eight Ten . Boys Six . . Eight Ten . Right hand 23.6 27.6 26.2 Right hand 26.8 31.2 33-2 Left hand 22.5 25.0 25.6 Left hand 22.6 28.0 32.8 In two cases the left hand grip is greater than the right. One Six boy has a record of sixteen kilograms for the right hand and eighteen for the left hand ; one Eight girl has a record of 25.5 for the right and 26 for the left hand. The difference between the right and left hand grip is not very large, but it is sufficient to show a difference, and that the feeble-minded is not necessarily ambidextrous as is sometimes claimed. The norms given by Smedley for i8-year-old boys and girls are as follows. TABLE III Boys Girls Right hand Left hand Right hand Left hand 49.28 45-01 27.75 2 7-66 Comparison with tables i and 2 show that the feeble-minded fall considerably below the normal for eighteen year old boys and girls. And the difference is greater between the feeble- minded boys and normal boys than is the difference between feeble-minded girls and normal girls. Experiment 2. Judgment of Movement. As a test of ability to perceive and estimate the extent of 8 ORDAHL a simple movement, the following experiment was performed. In a meter stick, five holes large enough to accommodate a small iron spike, were drilled at such distances that the space between the hole in the middle of the bar and the inside edge of one hole to the right and one to the left was twenty centimeters, and to the two extreme holes forty centimeters to both sides. A flat wooden slide about one centimeter wide was made to lie flat across the bar and slip easily along its surface where the first finger was rested firmly upon it, and the arm moved to and from the body. The meter bar was clamped to the side of a low table before which sat the subject, and opposite him the experimenter. The whole operation was concealed from the subject by means of a cardboard screen placed horizontally between his hands and eyes. The instructions given were: "Place your first finger on the little wooden slide, move away from you when I say 'down' until you hit against the peg. When I say 'back' move back until you hit the nail right in front of you. Move out again on 'down' and so on. When you have made the movement three times, I shall say 'gone' and remove the peg; then you are to move to where you think you stopped before." The signal words "down," "back" and "gone" were given at a definite rate, one every half second, "gone," of course, being the seventh. After a few preliminary trials to insure proper comprehension of the instructions, regular work began. Five trials in each direction and to each of the two distances from the center constituted the twenty judgments comprising one day's work, and six days a complete set. Table 4 gives in terms of centimeters the average amount of error for each age. Since there is no evidence of learning present, single day's results are not given. Av. Errors S + S D.V. A.D. 3.0 2.1 .9 3.0 .8 1.3 2.6 2.0 .8 2.8 .9 1.0 1.8 .8 ,9 1.7 .5 .7 Columns headed "+" show errors of over-estimation ; " " under-estimation ; "S" the entire number of errors in any one 20 40 TABLE IV R L + S + S + - S + _ Six . .3.3 .3 3.6 .9 1.3 2.4 2.1 .8 2.9 2.1 .9 Eight .2.5 .4 2.9 1.4 1.3 2.7 2.0 1.0 3.0 1.9 .7 Ten . .1.0 .5 1.5 .6 1.3 1.9 .8 .9 1.7 .9 A DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 9 rubric. Portions of the table headed "20" and "40" give the re- sults for both hands for the distances of 20 and 40 centimeters respectively. Those headed "R" and "L" give the results for both distances for right and left hands respectively. Under "average errors'' stand the average results for the entire 120 judgments made by each subject. Therefore, column "S" under "average errors" should be the same as the average of column S under 20 and 40, and the same as the average of columns under R and L. Column li D. V." stands for the average variation of each individual's single day's work from his average for the six days. Column "A. D." shows the variation of one individual of an age group from other members of that group. On the whole the difference between the three age levels is almost insignificant, the process probably being too nearly on a mechanical level to be much affected by superiority or inferiority of intelligence, but wihat difference exists, is in favor of the higher levels. The D. V.'s indicate that the Tens are steadier in their work than lower ages, and the A. D.'s that there is less variation of one member of the group from the others of the group than there is with the two lower mental ages. The most interesting facts come out in comparing the plus and minus er- rors, particularly under 20 and 40. Under 20, we see that the Sixes made a great deal larger plus than minus error. The Eights show quite a considerable plus error, while the Tens show little difference either in under- or over-estimation. Thi? means, as observation of the work also showed, that the lower levels exerted poor judgment in making too great an innervation for the distance they had to cover. They swung back and forth between the pegs with a jar and trusted to the pegs to confine their move- ments without trying to estimate the movement they were mak- ing, or to be guided by their estimation in their final judgment. Hence, the impetus of this impulse carried them beyond their former stopping place. In the judgment for 40 centimeters of movement, more inhibition is to be overcome in making the larger movement, and therefore this tendency is not in evidence. There is practically no difference between the accuracy of the two hands, as is seen from results under R and L. When re- io OKDAHL duced to per cent, of difference we have: Tens, 100; Eights, 36; Sixes, 24. The results seem to indicate that the process here is of so simple and elementary a nature as to have little depend- ence on degree of intelligence, and that what difference exists, is probably due to the fact that higher levels comprehend and obey the directions of the experiment more exactly than sub- jects of less intelligence. Experiment 3. Simple Reaction time to Sound. The apparatus used was Ewald's chronoscope and reaction keys. The subject was instructed to hold the lever down and let it fly upon hearing the click of the metal hammer. This metal hammer made electric connections and started the chronoscope. The release of the lever broke the circuit and stopped the chron- oscope, which counted the vibrations of the vibrator, vibrating at a twenty-fifth of a second. The subject seemed to find less difficulty in letting the lever go than in pressing it down. The act of holding the lever down seemed to keep him in a more fa- vorable attitude for receiving the "ready" signal and reacting to the sound. Whereas, if he held the lever tightly between the fingers in preparation for the signal, attention was apt to scatter. The subject was seated behind a screen so as to shut off all view of the apparatus and experimenter, but where the ex- perimenter could observe the position and movement of the sub- ject. Preliminary trials were given so as to accustom the sub- ject to the apparatus and to acquaint him fully with the object of the experiment. In the regular series 20 trials were given each day for five successive days, or until 100 reactions were taken. The results for the age groups, and for boys and girls together, are given in Table 5. TABLE V Mental Age Group average A. D. Six 4115 .1302 Eight 2759 .0236 Ten 2385 .0311 By this table we see that the Eights are superior to the Sixes by .1356 second, and the Tens stand .0374 above the Eights. DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 11 Considering the highest score as 100 per cent., the difference be- tween the mentel levels is indicated as follows. Tens, 100 per cent. Eights, 85 per cent. Sixes, 28 per cent. For the feeble-minded this experiment involves much more than simple voluntary processes. For them, it requires an act of volition of considerable complexity. The Six finds it an almost insurmountable problem to attend to one of the two foci, viz., the grip on the lever and the hammer click about to appear. To focus attention upon the grip and at the same time to maintain an anticipatory attitude in the margin of consciousness for the sound of the hammer is too much for him, and to associate two images effectively is out of the question. He must attend as well as he can to one stimulus, forego any effectual anticipatory im- agery and make his association after the second stimulus ap- pears. This is true, but in much less degree, of the Eights and Tens. The experiment is valuable, however, in showing the difference between the various levels of intelligence in the ca- pacity for what to normal adults is a simple voluntary process. Experiment 4. Tapping Test. As a test of sustained attention and voluntary effort, a simple tapping test was used. The apparatus consisted of a telegraph key clamped to the table and connected with an electric counter. A bell was connected with a pendulum to ring every five seconds, and the experimenter with little difficulty learned to read and record the counter on the tap of the bell. The subject was in- structed to tap with the tip of the thumb and first finger as fast as possible, until told to stop. The counter was in his full view as he worked, to act as a spur, and praise and flattery were lib- erally indulged in to procure maximum effort. The series re- quired 24 minutes to perform, and consisted of tapping alternately with the right and left hand twice, for one minute each, with an interval of five minutes between successive periods of tapping. Table 6 gives the numerical results of the experiment for the dif- ferent mental ages. The figures give the average number of taps made for each age for each ten-second period. Thus Six, column 12 ORDAHL 3, shows the average number of taps made by the Sixes in the third ten seconds. A. D. is the average deviation of each indi- vidual of that age from the general average of the group. TABLE VI 1 23 4 5 6 Av. A.D. Six 42.3 45.0 43.6 42.5 41.7 45.9 43.0 .44 Eight 44.8 47.8 47.0 46.3 45.8 45.7 46.4 .49 Ten 54.1 53.7 52.1 51.0 51.6 50.4 51.0 .22 There is some superiority of each age over the next lowest age, but not as much as might be expected from the results of other experiments. The most interesting fact is the shape of the curve of a minute's work for the three ages. The Sixes start low, rise a little after ten seconds, and drop gradually until at the end of the fifth ten-second period they are below their start- ing point, when they spurt on the last lap to their highest point. This general tendency is interesting in showing the inhibition to be overcome in the initial warming up process, and the quick fatigue in the middle of the course. Yet, the possibility of the sudden high rise at the end shows that, though the subject be- lieves he has been exerting himself, he has really been loafing at his task. The Eights start a little higher than the Sixes, rise by the end of ten seconds and begin to descend slowly until the close, when they are still higher than at first. Here is seen some inhibition at the beginning, but a greater capacity for sustained effort after speed is once up. However, the great variation among the Eights themselves makes any figures for them of only general value here, for half the Eights resemble Tens in character in this work, and a third, Sixes. The curve for the Tens starts highest and after the second ten seconds gradually decreases until it reaches its lowest mark at the end. The effort put forth does not allow them to recuperate at the end for a spurt higher. All subjects except one left-handed subject showed a higher average with the right hand, which of course, is the most prac- ticed and the least fatigable. As a means of further studying the fatigability of the dif- ferent levels, the averages were computed for the first two trials, and the second two trials separately. Table 7 gives the results. Under I is given the average of the first trial with both right DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 13 and left hands; under 2, the second trial with each hand. Av. gives the average for girls and boys. The figures show that the second trials are poorer for the Sixes than the first trial, while for the Eights and Tens, they are practically the same. TABLE VII Six Eight Ten 12 12 12 Average 49.2 43.1 46.9 46.5 50.6 50.6 This greater fatigability of the Sixes is partly due to fatigue of attention, but probably for the most part to the fact that they all pounded the keys with great energy and were physically somewhat fatigued by the time they had finished. This ex- penditure of effort on their part occurred despite the fact that they were all told frequently to tap easily, and were shown how to do so. It is just this lack of judgment displayed here that many students of the feeble-minded find so characteristic. In terms of per cent, the difference between the mental age groups is : Tens, 100 per cent. ; Eights, 89 per cent. ; Sixes, 82 per cent. Experiment 5. Visual Attention Span. The material used in this experiment consists (i) of three series of exposure cards, A, B, and C, the first five of each of which are given in Plate I ; (2) sheets of paper containing twenty squares, each divided into four smaller squares similar to the ex posure cards but lacking the stub lines. The apparatus used for exposure was Whipple's Tachistoscope. Each series of exposure cards contained twenty two-inch squares, each divided into four equal squares. Short stub lines one-quarter inch long were dis- tributed variously around the sides and corners. These lines may be placed across the corners, project from the middle of the sides at an angle of ninety degrees or forty-five degrees; never at any other angle or position. Series A has one stub line in each exposure card. Series B has two stu'b lines and Series C has three. The subject was required to observe the position and angle of the stub lines and to insert them in blank squares placed be- fore him. The exposure interval was sixty sigma. The subject was seated at a distance of four feet from the exposure window with eyes approximately on a level with the fixation point. The ORDAHL Plate I / y _^ - 2 2 2. ' / / \ 3 3 3 V f J - If- i ^ N - 1 1 5 4- ^ ' X 1 S DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 15 following directions were given each subject before beginning the experiment: "Notice the short lines are always across the corners, in the corners, or, as you see, at the middle of the side and turned either straight or slanting. I am going to drop some of the cards before the window. You watch carefully for the short lines so you can remember where they are and put them in the square before you just where they should be." From five to ten trial cards were then exposed first for a longer and then for a shorter interval. As soon as the subject seemed to com- prehend the problem and to have adjusted agreeably to the situ- ation, the regular series was begun. If, however, at the end of the ten trials it appeared there was no adequate comprehension, the subject was allowed to copy from the trial cards into the blank square until he understood what was wanted ; then the trial series was repeated. This last procedure was necessary with all but two of the Sixes : all but two of the Eights, and all the Tens adjusted to the experiment before the tenth trial some almost immediately. The score was obtained by counting the number of stub lines correctly placed. Each subject was put through each se- ries once each day for ten successive days. The time required for a daily sitting of sixty exposures varied between 15 and 20 minutes. The daily average number of correct cases for the different age lev~lr is shown in Table 8. TABLE VIII 1234 56 7 8 9 10 Av. A.D. SERIES A Six 7 6.7 7.7 8.0 7.2 7.5 7.3 7.3 8.1 9.0 7.5 2.23 Eight 12.9 12.9 14.1 14.6 14.7 16.1 16.4 16.4 15.7 17.3 15.1 2.6 Ten 14.0 14.3 16.2 17.4 17.2 16.6 16.6 16.8 17.6 17.7 16.4 2.99 SERIES B Six 5.9 6.9 6.4 8.1 7.5 8.2 8.9 7.9 6.9 7.0 7.39 2.36 Eight 13.9 13.7 15.9 19.5 18.2 19.5 20.9 22.4 20.8 23.5 18.1 4.66 Ten 17.7 18.3 20.0 20.7 20.4 21.0 22.4 22.5 23.9 24.0 21.04 5.34 SERIES C Six 6.3 5.7 6.0 6.9 7.1 7.7 5.8 5.4 6.8 10.0 6.77 2.35 Eight 15.3 15.1 16.9 16.6 18.5 18.7 18.4 20.2 19.9 23.9 18.31 5.43 Ten 17.7 18.8 19.0 22.9 24.4 24.5 24.3 27.1 27.0 26.0 23.17 4.31 In series A the Tens score an average of 1.30 above the Eights. This difference alone is not sufficient to indicate a real superiority, but this low score on the part of the Tens is due to 16 ORDAHL the fact that they were doing so well that they could not feel the necessity of doing better. The Eights' score was slightly over double that of the Sixes. The relation of the three levels to each other stand as follows : For Series A: Tens, 100 per cent.; Eights, 92 per cent. ; Sixes, 45 per cent. For Series B: Tens, 100 per cent.; Eights, 84 per cent. ; Sixes, 35 per cent. For Series C: Tens, 100 per cent.; Eights, 79 per cent. ; Sixes, 28 per cent. It will be seen from the total average column of Table 8 that the difference between the achievements of the different mental ages increases from series A to C, or with the increasing difficulty of the series. In series A, the Sixes are 45 per cent, of the Tens, while the difference between the Tens and Eights is only 8 per cent. In Series B, the Sixes are 35 per cent, of the Tens, while the difference between the Tens and Eights in- creases to 16 per cent. In Series C the Sixes fall to 28 per cent, of the Tens and the difference between the Tens and Eights is 21 per cent. The A series is not a real test for ages above six. The Eights score 75 per cent, and the Tens 82 per cent, correct cases. If we consider this score alone, it appears that it is difficult enough, but the experiment did not create a sufficient demand for effort. It was easy enough after a few trials to observe the correct position of one stub line and consequently there was not sufficient effort put forth to prevent one from slipping by occasionally. On the other hand, 35 per cent, of the correct cases would indicate that the test is too difficult for the Sixes. But their behavior and attitude toward the problem showed a clear comprehension and a general endeavor to score, which would at least indicate that the A series is a good measure for effort of attention. At the same time it gives the subject an opportunity to show whether or not he belongs to a higher level of intelligence. The Eights make their highest score in Series B. Likewise the learning curve is higher here than in Series C, indicating that C is too difficult, either because they become DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 17 discouraged and cease to exert maximum effort, or because the effort to grasp three stub lines at one exposure causes confusion of imagery. The Tens make their highest score in Series C, also their learning curve rises highest in this series. There are a few cases in which three stub lines are scored at one exposure, but this represents the maximum of effort. If a subject scored three stu'b lines at one exposure the score for the next exposure immediately following was sure to fall to one. and more likely to zero. In consideration of scores made and peculiarities of the groups of Eight and Ten already mentioned, the norms for the experiments should be as follows. Sixes should score 6 in five trials in Series A. Eights should score between 15 and 20 in five trials in Series B. Eights should score between 15 and 20 in five trials in Series C. Tens should score between 20 and 25 in five trials in Series C. The learning element in this experiment is small. It is hardly at all perceptible for Sixes and not large in either of the other two levels. If comparison is made between the average for the first five trials and the average of the second five trials of each series, the results stand, as given in Table 9. TABLE IX Series Six A Eight A Ten A 81x B Eight B Ten B Six C Eight C Ten C In this experiment each series was repeated ten times. In Table 9 the left hand column of figures shows the average cor- rect score for the first five trials of the series. The middle col- umn gives the average correct score for the last half or the last Av. for Av. for Gain in first half second half second half 6.10 7.60 1.50 13.84 16.38 2.54 15.82 17.06 1.24 6.76 7.78 1.02 16.22 21.32 5.10 19.42 22.76 3.34 6.40 7.14 0.74 16.48 20.22 3.74 20.56 25.78 5.22 i8 ORDAHL five trials. The right hand column gives the gain made in the last half of each series. There are only two cases out of the thirty who show any drop at all in the second half and these proved to be of an unstable nervous temperament. The Sixes make very little gain in any series. The gain for the Eights in Series B and the gain for the Tens in Series C is rather light, but greater gain is made by the end of the first half of the series, or by the fifth or sixth trial, so that the gain is made by holding the score reached by the end of the first half. In order that the test may be uniformly one of attention span, each position of the stub line in Series A should be as difficult as another, and in Series B and C, each group of stub lines, or the stub lines grouped in one exposure should be as difficult of per- ception as the group found in any of the other exposures of the series. This does not seem to have been the case, and it is per- haps not possible to distribute the lines over the field so as to make the large squares of equal or of a graduated difficulty of perception. In Series A, Nos. 10, 19, and 20 gave special diffi- culty, and there was a general tendency to get the lines of jthe lower square into the upper squares. In Series B, No. 13 was easiest, No. 16 quite as difficult as any. In Series C, No. 8 was among the first to be gotten correctly. In general, the lines about the center of the square where distances were less, were the most confusing. Two lines in the same small square close together or on the right or left side of the large square pre- sented less difficulty, also lines of similar quality. There seems to have been confusion when the line of vision passed the cross lines of the large squares. This may be due to the tendency of the eye to follow the lines or simply to the 'greater complexity of the perceptual image. It would seem that one large square with the stub lines distributed around the sides and corners might make a test more nearly free from the disturbance of ex- ternal factors. Something on this order would have the advan- tage of greater simplicity, and the stub lines could be more easily grouped in order of difficult. The experiment has revealed three differences in the mental levels chosen, viz., differences in comprehension of simple prob- DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 19 lems, adjustability, and attention span. The first two are not measurable in mathematical terms for this experiment but can be indicated. The Sixes had virtually to be put through the experiment before they could comprehend it, and they required the longest time to adjust even inadequately to the situation. The Eights can comprehend more easily, but required concrete demonstration, and adjusted more slowly than the Tens. The Tens comprehended from a verbal explanation and took up the proper attitude for work and adjusted most readily within five minutes. Differences in attention span are fairly represented in terms of percentage: Tens, 100 per cent.; Eights, 84 per cent.; Sixes, 45 per cent. Experiment 6. Discrimination of Grays. As a test of sensory discrimination, matching different shades of gray was used. The apparatus consisted of a card board about 12x18 inches, in which were fifteen openings two inches square, arranged in three rows of five squares each. In each square, except the middle one, were pasted from one to fourteen thicknesses of white tissue paper, one thickness in the first increasing by direct increment of one up to fourteen. Around the middle opening were arranged strips of cardboard to form a casing in which to slip small square frames. There were four- teen of these frames consisting of two-inch square pieces of white tissue paper, each frame holding thicknesses varying from one to fourteen pieces to correspond with the openings in the large card. The card with the fifteen openings was pasted flat against a ground glass window with a north light, and the sub- ject seated directly in front of it. (Of course the light showing through the papers would produce the brightest gray in the square with one thickness of paper and the darkest for the four- teen thicknesses). A small frame was then slipped into its place in the middle opening, and the subject told to "point to the gray just like this one." A constant irregular order was used to in- sure procedure without knowledge of the subject. Matching each of the fourteen grays twice comprised one day's work, and 20 ORDAHL three days, or eighty-four judgments for a subject, constituted a test. All subjects comprehended the task readily, yet it was diffi- cult to get some of the lower grades to take the time and pains to really discriminate. Then, again, three of the Tens took so much time to make their decisions that after-images and fatigue must have had something to do in affecting the value of their judgment. In scoring a judgment, the amount of error for that judg- ment was estimated by the distance in the scale of grays lying between the gray chosen as identical with the standard and the one actually identical. For example, if gray number 14 was shown, and the number 12 pointed to as identical, the error was recorded as 2, or if 13 was chosen when 10 was shown, the error amounted to 3. The average for each day's trials was taken and the average for the entire three days' work. Since there was no evidence of effect of practice, only the average results are given, which are contained in Table 10. TABLE X Six Eight Ten 2-7 i-5 i-3 The errors for all levels are surprisingly few, though Sixes show a score of errors twice as large as that of the other ages. The three levels would have been more nearly equal but for four very careless Sixes. In term of relative percentage it amounts to, Tens, 100; Eight, 98; Sixes, 80. The following table gives the average error for each particular gray, ranging from one, which stands for bright- est, to 14, the darkest. Naturally the easiest grays to discrim- inate in this series are the brightest, and the most difficult the darkest. TABLE XI 1234 5678 9 10 11 12 13 14 Six 2.7 2.7 2.3 2.0 2.6 2.2 2.7 2.7 2.8 2.9 2.9 3.0 2.6 3.0 Eight 0.6 1.1 0.8 1.6 1.8 1.3 0.9 2.2 2.4 1.9 2.3 1.6 0.7 0.4 Ten 0.2 0.8 0.8 1.2 1.3 1.2 1.6 2.6 1.8 2.2 1.9 1.8 1.1 0.6 The Sixes make about the same amount of error for each DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 21 gray, showing that it is not for them so much a matter of diffi- culty of discrimination, as whether they could attend closely enough to compare. The Eights show more nearly the error curve we should expect, except in the big drop in the middle at seven. Here again attention is the factor which explains, for seven was to the left of the window into which the variable gray was slid, and the one with which it was natural to compare it. Hence, fewer mistakes were made here than might be ex- pected. The experiment, on the whole, does not seem a particularly good one for detecting differences in mental levels. In fact, re- sults indicate that when an imbecile can be induced to attend, his powers of discrimination are about equal to those of a moron. But the fact that he concentrates perfectly one minute and wanders the next, makes the results less valuable as criteria of discriminability than of attentive capacity. Experiment 7. Judgment of Forms. It is quite evident that feeble-minded children and adults have sensations not greatly different from normal persons ex- cept in the time of response. The difference, then, should lie in what might be termed the manipulation of mental elements or mental imagery. We have attempted an experiment which should test the relative ability of the different mental ages to receive, retain and transfer imagery from one sense to another. A number of forms were cut from thick pasteboard and mounted on other pasteboard cards five inches square. The subject was allowed to pass his hands under a cloth screen and to feel of the form by passing his fingers around the edges and over the top while it was held in a stationary position. After this he was required to point out the form just felt among the ten forms drawn full size on one large card. The subject was given directions as follows: "Put your hands under this cloth and feel of a form there something like this one, until you are sure you know what it looks like, then I will let you see these drawings, and you are to point out which one you have just felt." The series was presented once each day for five successive ^i ORDAHL days, one trial being allowed for each form, or 40 trials in all. The results are given in Table 12. TABLE XII Av. daily Av. total errors errors A.D. Six 5.6 6.8 7.1 6.7 6.5 6.54 4.32 Eight 4.2 3.8 4.9 1.2 1.2 3.07 4.00 Ten 3.7 1.6 3.4 1.7 1.45 2.37 4.32 According to Table 12 the average errors for five trials is not large for Eight and Ten. In terms of per cent, the difference between the levels stands thus : Tens, 100 per cent. ; Eights, 90 per cent. ; Sixes, 45 per cent. Following the daily score from left to right, it will be noted that learning is quite rapid for Tens and Eights. When we add to this the fact that errors were almost constantly made on three particular forms, the experi- ment does not appear to have much value. It may, however, be a test of superficiality since it would have been quite possible for the Eights and Tens to have made an almost perfect record. They were satisfied with approximate certainty. The character- istic to be content with approximate results and to overlook small but essential differences is not so apparent in experiments that at once challenge effort and put the subject on his mettle. Experiment 8. Judgment of Forms, Two Dimensions. On account of the relatively unsatisfactory results found in experiment No. 7, that experiment was modified and another ex- periment attempted. This contains the same forms as Experi- ment No. 7, but they were rendered more difficult by cutting off corners and thus changing their shape. The procedure was further changed by allowing the subject to observe the forms he had felt instead of the drawings of them. This changed two factors simultaneously with the result that we cannot ascribe difference in results to either of the two factors, more difficult forms, and the observations of actual forms instead of drawings of them. However, a few forms were not changed but remained the same for both experiments, 7 and 8. Comparison of the blanks for both experiments show only a very slight improve- ment in Experiment 8 for forms not changed, while for the changed forms, the score immediately drops off. This would in- DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 23 dicate that there is little difference in observing actual forms or drawings of the forms. However, there was a greater interest in choosing the correct forms from the real forms than from drawings. The results of the experiment are given in Table 13. TABLE XIII Av. daily errors Av. 12345 errors A.D. Six 8.4 9.2 8.4 8.2 7.9 8.52 4.16 Bight 5.3 4.2 4.3 4.4 2.8 4.26 5.96 Ten 3.4 2.7 3.6 2.0 1.6 2.66 4.29 The relative differences between the age levels are : Tens, 100 per cent. ; Eight, 78 per cent. ; Sixes, 20 per cent. The differences here in scores are more marked than in Experiment No. 7. There is need for greater attention ; discrim- ination is finer and the process of identification more complex. And yet it appears that the fundamental process is one of trans- fer of touch and kinaesthetic imagery to visual imagery. It is probable, however, that the discrimination is due to practice in alternate feeling and seeing since an expression of recognition is made on feeling of an object which has been, just previously, the focal point of attention. It becomes, therefore, the recall of a visual image through touch and the recognition of this image through vision. In feeling of an object not yet seen, the image is indefinite until it has been seen. W'hen the second touch- motor experience takes place, the process is simultaneously touch-motor-visual. The test is not a good one for the Sixes. The children of this level do not have the necessary capacity for sustained con- secutive thought. The low score would indicate that the Sixes are out of court here. Chances are one in ten for a correct score, which lowers the actual choice and renders the test unfit. Be- sides the attitude in rendering a choice indicates they were mak- ing a wild guess. The problem is entirely within the capacity of the Eights and Tens, but Experiment 8 is superior to Experiment 7, since it calls for clear attention and finer discriminations. The norms for this test should be 50 per cent, correct for Eights and 70 per cent, for Tens. 24 ORDAHL Experiment g. Judgment of Sizes, Two Dimensions. This experiment was designed for the same general purpose as seven and eight, and is constructed on the same plan, except that the forms remain constant while the size varies. Four dif- ferent forms were used, the circle, rectangle, triangle and square. These sizes were made from heavy cardboard and mounted on cards five inches square. The procedure was the same as in Experiment 8. The dimensions for the forms are given in Table 14. TABLE XIV Circles Diameter Squares Side Rectangles Triangles Base Altitude 1. 1% In. 1. 1% in. 1. 1 x2 in. 1. 1% in. 1% 2. 2 in. 2. 1% in. 2. I%x2^4 in. 2. 2 in. 2 3. 2% in. 3. 1%. in. 3. iy 2 x2% in. 3. 2% ia. 2% 4. 2% in. 4. 2 in. 4. I%x4 in. 4. 3 in. 3 5. 2% in. 5. 2% in. 5. I%x3 in. 5. 3% in. 3% The forms were presented once each day for five successive days, thus making 20 trials each day, or 100 trials in all. Errors were determined by counting the number of places a size was removed from the correct place, e. g., if the subject judged No. i to be No. 2, the error would be one. If No. 3 was judged to be No. 5, the error would be two. Since there are five sizes called for in each form, the highest possible error for any judgment is four, and for the four forms given at one sitting is 80. It would therefore be possible for a subject to score 400 errors for the five sittings. Table 15 shows the results for this experiment. TABLE XV Av. daily errors of all fcrms Av. A.D. Six 19.9 21.4 18.3 20.0 19.0 19.9 Eight 11.8 8.7 8.6 8.3 9.0 9.2 2.0 Ten 8.7 6.5 6.6 5.1 4.0 6.1 1.5 This experiment is too difficult for the mental Six. It was quite evident that his judgments were largely accidental. How- ever, his error for any one judgment is rarely over two, but com- monly one. The Eights and Tens comprehend the problem readily and have very definite feelings as to the correctness of their judgment. However, in the first trials there is a feeling of uncertainty, and the subject will remark: "Well, I don't know, I am guessing." The guess, however, is more often correct than DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 25 otherwise; so much so that one is inclined to infer that the touch and kinaesthetic image is directing the choice, although it has not yet quite fused with the visual image. One form was about as difficult to judge as another. The differences between the various ages are as follows: Mental Tens, 100 per cent. ; Eights, 77 per cent. ; Sixes, 7 per cent. This test might be a serial test beginning with the six-year level if a score with error one is considered normal for the Sixes. In this case there should be allowed no more than 10 per cent, of error in going through the four series once. The Tens should be able to go through the four series once with no more than 25 per cent, of error, the Eights with 35 per cent, of error. Experiment 10. Judgment of Forms, Three Dimensions. It seemed from the behavior of the subjects in Experiments 8 and 9 that discrimination involving variation in three dimen- sions instead of two might involve a more complex mental pro- cess in the transfer of touch into visual imagery. Twenty hard- wood blocks were cut out, ten with the dimensions 2 in. by 2 in. by 2 in ; ten 3 in. by 2 in. by I in. These blocks were then shaped into a series somewhat on the pattern of the forms used in Experiment 8. The blocks are given in Plate II. It was at- tempted to make these forms into a series of graduated difficulty of perception, but results show that some represented much greater difficulty than others. The same procedure was followed in this experiment as in Experiment 9, except that the blocks were held stationary by two small holes bored in each block which fitted over two brads driven into the table just before the subject, and the blocks were placed in four rows always in the same order. The subject was put through the series once each day for five successive days. The results are given in Table 16. TABLE XVI Av. daily errors 1 23 45 Av A.D Six 15.7 15.9 15.5 15.5 15.2 15.56 7.5 Eight 11-0 10.4 8.1 7.4 5.8 8.44 5.8 Ten 5.8 4.6 4.6 2.7 2.1 3.06 4.4 The above table shows the same characteristic group differ- ORDAHL Plate II 6 8 9 17 10 H 14 18 19 16 DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 27 ences as are seen in Experiments 7 and 8. The Sixes can dis- tinguish very simple forms, but cannot proceed beyond these. The differences are: Tens, 100 per cent; Eights, 71 per cent., and the Sixes 21.4 per cent. A few forms were recognized by all the cube, the rectan- gle and the divided cubes. 6 and 7, were most often confused and presented difficulty to all subjects. The Tens adjust the most readily, the Eights more slowly and the Sixes not at all. The experiment offers opportunity to observe the readiness of ad- justment on the part of the subject. There are many forms so similar that they could be distinguished and differentiated only through trial and error. The psychological process is difficult to determine since introspection is much needed here for any- thing like a correct interpretation; but introspection is some thing the feeble-minded cannot furnish. A few illusions evi- dently arise which disappear only with direct comparison. A large portion of the form conies immediately as one passes the fingers over the blocks, or shoots into form as the fingers turn the corners or measure the angles. But even with this imme- diate flash into consciousness there remains a certain indefinite- ness to the imagery until the object is observed visually. After getting the touch and kinaesthetic experience it remains for the subject to retain the image against the visual perception of many forms, some similar, until the form identical with his image is sighted. The subjects differ apparently in two ways. One class was "impressionist" and the other "rationalist." The former are visualists and do not consciously turn over the im- agery mentally, but rely upon a feeling of familiarity to de- termine their choice as they looked over the field of 20 blocks. The second class would note similarities, but they would fix upon one essential difference and rely upon this factor for the choice of a block. Those who pursued the latter method were able sev- eral days after the last trial had been concluded to pick out the form felt when the blocks were piled miscellaneously in a heap on the table, without a single error. The "impressionists" were not able to do this and when asked to indicate how they dis- tinguished the forms one from the other, could not do so. Dis- 38 ORDAHL crimination by noting carefully the characteristics of the object was common to both Eights and Tens. But the Tens exercised more control than did the Eights. The experiment calls for per- ceptions of relations, capacity for forming clear-cut distinctions, and a certain small amount of reasoning. While it is not an ab- solute certainly, there are certain strong indications that it re- quires some mental effort to make the transfer from a touch- kinaesthetic imagery to visual, and that this experiment reveals the process in an elementary way. The experiment as a whole was more interesting to the subjects than Experiment No. 9, and for this reason is superior as a mental test. Experiment u. Memory for Geometrical Forms. As a test of simple visual memory, ten cards, each contain- ing a geometrical form were used. Each form consisted of a cir- cle two inches in diameter, with the diameter drawn through it horizontally, vertically, or at 45 degrees from either horizontal or vertical, one or two one-inch lines lying outside the circle as tan- gents, and one or two one-inch tines lying inside as chords, there being always four such lines in all to a circle, as shown in Plate III, A. Since each drawing was entirely different, by turning a card in each of the four possible positions, forty instead of ten variations of form were produced. The cards were placed in two parallel rows on a table at which the subject sat, the order being a definitely planned ir- regular one, to avoid the factor of place memory. A cloth curtain hung before the subject to conceal operations. The subject was told, "I am going to show you a card with a drawing on it, study it, and after ten seconds I shall take it away, and you must pull the curtain aside and point to the one you have been studying." The card was slipped under tfhe cur- tain and shown to him for the ten seconds, and immediately put back into place, when he tried to pick it out from the other drawings. After the ten cards had been exhibited, they were placed in the second position, then in the third and fourth, thus making forty trials in a day's work. Three days' work of 120 trials for each subject constituted a complete series. DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 29 Plate III A B ORDAHL After the above experiment on immediate recall, a similar one was used for delayed recall, the only difference in method being that the subject waited ten seconds after having seen the card before he tried to select it from the others. Here, owing to necessity of leaving experimentation entirely, only two days' records were taken and only twenty judgments on each day, making forty the total number. In a third experiment the delay was extended to one min- ute. Since only ten judgments could be allowed here, the results do not bear a value entirely comparable with those of the first two forms of the experiment, but the results are given for what they are worth. Table 17 gives the average percentage of correct cases for each age of the three forms of the experiment. TABLE XVII Six Eight Ten There is quite a distinct and remarkable difference between the different age levels. The Sixes do practically nothing, the Eights get about half, and the Tens more than three-fourth. The task of discriminating the differences between the arrange- ment of meaningless lines was too complicated and difficult a problem for the weak attentive capacity of the Sixes. Memory hardly seemed a factor here, judging from their careless manner of studying the card during its exposure and the haphazard way in which they made their selection when it was time to judge what card they had seen- The Eights were more sensible in their methods, but it is probable that here, too, discriminability and attentive capacity was an important factor. Reduced to per cent, difference, the three ages stand : Immediate recall Sixes, 20 Eights, 72 Tens, 100 Immediate recall 16 10-second interval 2O 1-tninnte interval 2O it . s6 cc 6^ 77 DD OO u o 8<; DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 31 Ten seconds delay Sixes, 22 Eights, 60 Tens, 100 One minute delay Sixes, 23 Eights, 74 Tens, 100 For the Tens only is there any considerable difference be- tween the three forms of recall, who profit by the ten second intervals, and are but a little lower after one minute interval, though higher than in immediate recall. Individual figures show no learning for any age, except for the Tens, and here only a very slight degree. The experiment demands too great a degree of attentive ca- pacity for the Sixes, so that whatever value it might have as a measure of retentiveness is eliminated. Perhaps it is even a little too difficult for the Eights, but for Tens it might make a good mental test, if 70 per cent, or more correct judgments were required, with an improvement in the case of delayed recall. Eights should be required to get about half the cases right for immediate recall and do at least no worse in delayed recall. Experiment 12. Modified Typewriter. This was an experiment in learning a connected series of visual-motor coordinations. The apparatus used was an ar- rangement resembling in principle a simple typewriter of four keys. On each key was pasted a color, and when any key was pressed a different color appeared just above it, through a slot in a vertical screen, which was the color of the next key to be struck. A red key threw up yellow ; a yellow, blue ; a blue, green, and green, red, the last key of the series throwing up the color of the first, making an uninterrupted process to be continued un- til a signal to stop. Each key was connected with an electrical counter, so that every stroke registered a count. A bell was con- nected with a second pendulum to ring once every minute, as a signal for starting and stopping. The errors were easily ob- served and recorded by the experimenter. After the principle 32 ORDAHL of the apparatus and the task was explained briefly to the sub- ject, he was allowed a few trials to make sure that he understood. Every subject was instructed to use four fingers, the first and middle fingers of both hands, and to strike each color with its own particular finger. But the latter was impossible for some subjects, and though all were given the same instructions, only part of them succeeded in using four fingers. Ten one-minute trials a day with a minute interval between successive trials and six days' work constituted a regular series. When results in- dicated that the subject might be able to work without the aid of the visual cue, a cardboard screen was placed to conceal both the colors on the keys and the small colors the keys showed on being pressed. Where a subject could not work without the aid of vision at the end of six days of practice, the series was con- tinued for four more days. The numerical results s'how only six days' work. Throughout, the subject was kept informed as to the score and mistakes. The problem for the subject then involved a series of four motor reactions to specific visual cues. It comprised the perception of the color shown through the slot, the perception of the key with the same color pasted on it, the choice motor re- action involved in the pressure of that key, and the choice of the finger used. Table 18 shows the results in numerical form for the differ- ent mental ages. "S" indicates the number of strokes in a min- ute, "E" the number of errors, and "C" is "S" minus "E," or the correct strokes. The figures at the head of the columns indicate days. Thus the figure under Six, column 6, "S," stands for the average strokes made by the Sixes on the sixth experimental day. Column A. D. gives the average deviation of each individual of the group from the average for that group. ENCES BETWEEN LEVELS OF INTELLIGENCE 33 TABLE XVIII SIX DayS ~ 1 2 3 4 5 6 Av. A.D. h 27-0 35.2 42.7 48.9 53.3 61.8 45.5 E 4-3 4.9 4.5 5.2 6.6 7.0 5.8 C 22.7 30.3 38.2 43.7 46.7 54.8 39.8 21.8 EIGHT S 50.8 81.8 114.3 128.0 138.3 147.4 111.0 E 5.7 5.7 6.6 9.7 6.1 2.1 5.0 C 45.1 76.1 107.7 118.3 132.2 145.3 106.1 44.4 TEN S 85.4 151.3 187.5 217.7 246.9 281.8 201.7 B 4.7 2.9 1.7 1.6 2.8 2.1 2.7 C - " 8-7 148.4 185.8 216.1 244.1 279.7 299.0 37.9 All ages show an increase from day to day, the sixth being about twice that of the first day's record. The Sixes start low- est and increase at the slowest rate, the Tens start highest and increase at the fastest rate, while the Eights show a result just between the two. The errors of the Sixes remain about constant, though the number of strokes increases, showing an improve- ment in accuracy; the errors of the Tens decrease, despite the great increase in strokes, giving a practically perfect record as to accuracy, while the Eights again show a middle tendency. Though the A. D. is large, it indicates rather a variation within the group than an over-lapping of the three groups. Further interesting differences of the three mental ages is seen in the following table, which gives the result of each trial for the first days' work done by the three levels. TABLE XIX Trials 123456789 10 Six 16.4 17.4 20.2 21.5 21.9 22.3 25.5 27.6 24.3 28.8 Eight : 29.7 35.1 34.8 42.0 42.8 47.3 48.5 49.1 57.8 61.7 Tea 47.8 67.6 75.3 87.8 99.4 98.9 108.2 110.4 117.6 120.7 As in the case of the record of the entire time, the Sixes start very low, the Eights almost twice as high as the Sixes, and the Tens twice as high as the Eights, while about the same relation- ship holds between each of the ten trials. In their manner of working, the subjects fell into almost as definite groups as their numerical results show. All subjects grasped the problem after some slight explanation, but the Sixes required more instruction and more practice before regular work could be started. Using four finsers, one for each key, seemed to 34 ORDAHL be the most difficult task of all and only two of the Sixes suc- ceeded in doing so, even after the tenth day- Half of the Eights managed it, with considerable difficulty, but all of the Tens were using four fingers by the end of the second day's work. Of course, this was a more economical method if it could once be acquired and resulted in a quicker mechanization of the process and a more rapid rate of work. For half of the Eights and all but two of the Sixes, it was too complicated a matter to distin- guish the proper one of the four fingers and use it when required, and no results would have been possible had they not been al- lowed to use only the index finger of each hand. Sixes with one exception were careless in their work, and many times they would push any key which happened to be the easiest, until urged to be careful. Three of the Eights were faulty in this respect, but rather on account of confusion result- ing from effort at high speed at the expense of correctness, while Tens were all anxious to make a high score, all were notice- ably more careful than the Sixes, or the average run of the Eights. There were varying degrees of interest on the part of the subjects in the problem itself, in the subject's own progress, both in respect to his own record and his relation to others. Sixes were all working only because they were told to, and any effort exerted was merely for the sake of approbation. Eights were interested at first and glad to work, but toward the end of the time became tired of the experiment and wanted to quit, or take up something new, yet when once at work they all seemed to put forth considerable, if not maximum, effort. One exception to the Eights is to be classed with the Tens. The Tens from the first were interested. There was a high degree of self rivalry, and of rivalry with each other. Each child knew his score, and remembered it to compare notes with the others later. Among the Ten boys this was very pronounced; so great was their de- sire to excel that all practiced the finger movement, whose se- quence they easily learned in the first and second day's work, and when in their playroom one used a table top, two a piano, one an organ, and one drummed in the air. The practice of the girls was all confined to work in the laboratory. DIFFERENCES BETWEEN LEVELS OF INTELLIGENCE 35 Only one Six was able to work with the keys and small colors concealed. One Eight managed it on the second day; five on the third ; one on the fifth ; one on the sixth, and two not at all, while all of the Tens succeeded by the beginning of the third day five on the first day, four on the second and one on the third. The experiment is a valuable one for indicating the ability of an individual to comprehend a simple explanation of details, his power of motor coordination, capacity for voluntary effort and sustained interest. It might be used as a simple test of in- telligence if ten trials were taken at one sitting. When accord- ing to our results a Six should comprehend the experiment, be able to use two fingers and have a record averaging about 20 correct strokes, with a moderate increase in his curve from first to last. An Eight should comprehend that he is to use four fingers and make some attempt to do so and reach an average of about 50 correct strokes. A Ten should us four fingers cor- rectly by the tenth trial and make an average of at least 75 cor- rect strokes. Experiment 13. Ink Blot Test. As a study of imagination an ink blot test was used, the ink blots being the first ten in the series of twenty described in Whipple's manual of Mental and Physical Tests. A card was shown to a subject to whom it was explained that "This blot was made by dropping a blot of ink and smear- ing it around. What do you think it looks like? Of course it is not exactly like anything, but what does it make you think of?" After giving all he could see in one position, the card was changed until it had been in all four positions. Two minutes were allowed, but most subjects refused to look longer than a minute and a half, and many would use less than one minute. This was particularly true of the Sixes and least true of the Tens. Naturally the experiment does not lend itself well to nu- merical classification, but we find, in a rough way, that the av- erage number of objects seen to a card are : 36 ORDAHL TABLE XX Sixes Eights Tens 1.6 2.8 3.2 This shows an increasing superiority in wealth of imagina- tion from the lowest to the highest grade. Reduced to terms of per cent, of difference, it stands : Sixes e O Eights 87 Tens I00 The Sixes found difficulty in seeing a different object in an ink blot i*brn on ce it had suggested anything to them, and no matter in what position this card was turned, the picture was apt to remain the same. The blot was to them not so much a sugges- tion of an object as an actual picture of that object. To a less extent this tendency existed among the Eights, but was hardly noticeable in the Tens. An occasional Six enumerated objects which the blot could not have suggested and which they could not point out When asked to do so. To all children the blots suggested mainly people and animals, but the Sixes only name the object, t