How To Find The I Q Of Adult Subjects
Native intelligence, in so far as it can be measured by tests now available, appears
to improve but little after the age of 15 or 16 years. It follows that in calculating
the I Q of an adult subject, it will be necessary to disregard the years he has
lived beyond the point where intelligence attains its final development.
Although the location of this point is not exactly known, it will be
sufficiently accurate for
ur purpose to assume its location at
16 years. Accordingly, any person over 16 years of age, however old, is
for purposes of calculating I Q considered to be just 16 years old. If a
youth of 18 and a man of 60 years both have a mental age of 12 years,
the I Q in each case is 12 / 16, or .75.
The significance of various values of the I Q is set forth
elsewhere. Here it need only be repeated that 100 I Q means exactly
average intelligence; that nearly all who are below 70 or 75 I Q are
feeble-minded; and that the child of 125 I Q is about as much above the
average as the high-grade feeble-minded individual is below the average.
For ordinary purposes all who fall between 95 and 105 I Q may be
considered as average in intelligence.