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


For example, of 104 adult individuals testing by the Stanford revision

between 12 and 14 years, an
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


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 case of a 10-year-old. Stating the error in

terms of the intelligence quotient makes it more evident. Thus, an error

of 10 months in the mental age of a 5-year-old means an error of almost

15 per cent in the intelligence quotient. A scale which tests this much

too low would cause the child with a true intelligence quotient of 75

(which ordinarily means feeble-mindedness or border-line intelligence)

to test at 90, or only slightly below normal.

Three serious consequences came from the too great ease of the original

Binet scale at the lower end, and its too great difficulty at the upper


1. In young subjects the higher grades of mental deficiency were

overlooked, because the scale caused such subjects to test only a little

below normal.

2. The proportion of feeble-mindedness among adult subjects was greatly

overestimated, because subjects who were really of the 12- or 13-year

mental level could only earn a mental age of about 11 years.

3. Confusion resulted in efforts to trace the mental growth of either

feeble-minded or normal children. For example, by other versions of the

Binet scale an average 5-year-old will show an intelligence quotient

probably not far from 110 or 115; at 9, an intelligence quotient of

about 100; and at 14, an intelligence quotient of about 85 or 90.

By such a scale the true border-line case would test approximately as


At age 5, 90 I Q (apparently not far below normal).

At age 9, 75 I Q (border-line).

At age 14, 65 I Q (moron deficiency).

On the other hand, re-tests of children by the Stanford revision have

been found to yield intelligence quotients almost identical with those

secured from two to four years earlier by the same tests. Those who

graded feeble-minded in the first test graded feeble-minded in the

second test: the dull remained dull, the average remained average, the

superior remained superior, and always in approximately the same


[18] See "Some Problems relating to the Detection of Border-line Cases

of Mental Deficiency," by Lewis M. Terman and H. E. Knollin, in _Journal

of Psycho-Asthemes_, June, 1916.

It is unnecessary to emphasize further the importance of having an

intelligence scale which is equally accurate at all points. Absolute

perfection in this respect is not claimed for the Stanford revision, but

it is believed to be at least free from the more serious errors of other

Binet arrangements.