How The Scale Is Used

By means of the Binet tests we can judge the intelligence of a given individual by

comparison with standards of intellectual performance for normal children of different

ages. In order to make the comparison it is only necessary to begin the examination of

the subject at a point in the scale where all the tests are passed

successfully, and to continue up the scale until no more successes are

possible. Then we compare our subject'
performances with the standard

for normal children of the same age, and note the amount of acceleration

or retardation.

Let us suppose the subject being tested is 9 years of age. If he goes as

far in the tests as normal 9-year-old children ordinarily go, we can say

that the child has a "mental age" of 9 years, which in this case is

normal (our child being 9 years of age). If he goes only as far as

normal 8-year-old children ordinarily go, we say that his "mental age"

is 8 years. In like manner, a mentally defective child of 9 years may

have a "mental age" of only 4 years, or a young genius of 9 years may

have a mental age of 12 or 13 years.