d over and made more definite with the idea of promoting uniformity. This phase of the revision is perhaps more  important than the mere relocation of tests. Also, the addition of numerous tests in the upper ranges of the scale affects very considerably the mental ages above the level of 10 or 11 years.

Effects of the revision on the mental ages secured.

The most important effect of the revision is to reduce the mental ages secured in the lower ranges of the scale, and to raise considerably the mental ages above 10 or 11 years. This difference also obtains, though to a somewhat smaller extent, between the Stanford revision and those of Goddard and Kuhlmann.

For example, of 104 adult individuals testing by the Stanford revision between 12 and 14 years, and who were therefore somewhat above the level of feeble-mindedness as that term is usually defined, 50 per cent tested below 12 years by the Goddard revision. That the dull and border-line adults are so much more readily distinguished from the feeble-minded by the Stanford revision than by other Binet series is due as much to the addition of tests in the upper groups as to the relocation of existing tests.

On the other hand, the Stanford revision causes young subjects to test lower than any other version of the Binet scale. At 5 or 6 years the mental ages secured by the Stanford revision average from 6 to 10 months lower than other revisions yield.

The above differences are more significant than would at first appear. An error of 10 months in the mental age of a 5-year-old is as serious as an error of 20 months in the ca