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
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.