some one line is usually, as all the work of
differential psychology shows, gifted more than the average in many
other lines. Opportunity decides in just what field his life work shall
lie; but he would be able to make a success in a number of fields.
Darwin born in America would probably not have become the Darwin we
know, but it is not to be supposed that he would have died a "mute,
inglorious Milton": it is not likely that he would have failed to make
his mark in some line of human activity. Dr. Cattell's argument, then,
while admissible, can not properly be urged against the fact that
ability is mainly dependent on inheritance.

We need not stop with the conclusion that equality of training or
opportunity is unable to level the inborn differences between men. We
can go even farther, and produce evidence to show that equality of
training _increases the differences_ in results achieved.

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