This evidence is obtained by measuring the effects of equal amounts of exercise of a function upon individual differences in respect to efficiency in it. Suppose one should pick out, at random, eight children, and let them do problems in multiplication for 10 minutes. After a number of such trials, the three best might average 39 correct solutions in the 10 minutes, and the three poorest might average 25 examples. Then let them continue the work, until each one of them has done 700 examples. Here is equality in training; does it lead to uniform results? Dr. Starch made the actual test which we have outlined and found that the three best pupils gained on the average 45 in the course of doing 700 examples; while the three poorest gained only 26 in the same course of time. Similar tests have been made of school children in a number of instances, and have shown that equality of training fails to bring about equality of performance. All improve to some extent; but those who are naturally better than their comrades usually become better still, when conditions for all are the same. E. L. Thorndike gives[12] the following tabular statement of a test he conducted: THE EFFECT OF EQUAL AMOUNTS OF PRACTICE UPON INDIVIDUAL DIFFERENCES IN THE MENTAL MULTIPLICATION OF A THREE-PLACE BY A THREE-PLACE NUMBER Amount done Percentage of per unit of correct figures time in answers Hours of Practice | | First 5 Examples First 5 Examples | | | | | Last 5 or 10 | Last 5 or 10 | | Examples | Examples | | | | | | | | Gain | | Gain Initial highest five individuals 5.1 85 147 61 70 78 18 " next five " 5.1 56 107 51 68 78 10 " " six " 5.3 46 68 22 74 82 8 " " six " 5.4 38 46 8 58 70 12 " " five " 5.2 31 57 26 47 67 20 " " one individual 5.2 19 32 13 100 82 -18 Similar results have been obtained by half a dozen other experimenters, using the tests of mental multiplication, addition, marking A's on a printed sheet of capitals, and the like. It would be a mistake to conclude too much from experiments of such restricted scope; but they all agree in showing that if every child were given an equal training, the differences in these traits would nevertheless be very great.