On the contrary, equalizing training seems rather to increase differences. The superior individual seems to have attained his superiority by his own superiority of nature rather than by superior past training, for, during a period of equal training for all, he increases his lead. For example, compare the gains of different individuals due to about 300 minutes of practice in mental multiplication of a three-place number by a three-place number shown in Table 14 below, from data obtained by the author ['08].[25] [25] Similar results have been obtained in the case of arithmetical and other abilities by Thorndike ['08, '10, '15, '16], Whitley ['11], Starch ['11], Wells ['12], Kirby ['13], Donovan and Thorndike ['13], Hahn and Thorndike ['14], and on a very large scale by Race in a study as yet unpublished. TABLE 14 THE EFFECT OF EQUAL AMOUNTS OF PRACTICE UPON INDIVIDUAL DIFFERENCE IN THE MULTIPLICATION OF THREE-PLACE NUMBERS ==================================================================== | AMOUNT | PERCENTAGE OF | |CORRECT FIGURES |----------------+--------------- | Initial | | Initial | | Score | Gain | Score | Gain -----------------------------------+---------+------+---------+----- Initially highest five individuals | 85 | 61 | 70 | 18 next five " | 56 | 51 | 68 | 10 next six " | 46 | 22 | 74 | 8 next six " | 38 | 8 | 58 | 12 next six " | 29 | 24 | 56 | 14 ==================================================================== THE INTERRELATIONS OF INDIVIDUAL DIFFERENCES Achievement in arithmetic depends upon a number of different abilities. For example, accuracy in copying numbers depends upon eyesight, ability to perceive visual details, and short-term memory for these. Long column addition depends chiefly upon great strength of the addition combinations especially in higher decades, 'carrying,' and keeping one's place in the column. The solution of problems framed in words requires understanding of language, the analysis of the situation described into its elements, the selection of the right elements for use at each step and their use in the right relations.