Developmental psychology.pdf

372 Individual Differences
IQ =
=
MA
CA
10
10
14
10
6_
10
X 100
X 100 = 100
X 100 = 140
X 100 = 60
Figure 14.5
Computation of the IQ. The
conventional formula is
MA/CA X 100. This procedure has
been modified to provide a deviation
IQ, but the conventional method
yields a rapid, close approximation.
16
14
12
10
8
6
4
2
A
В
С
ч I 1
1
/\
Memory General Verbal Problem
information fluency solving
Figure 14.6
Differences in Abilities. These
profiles all show an average score of
ten, but the subtest results are quite
different, indicating that persons with
the same general level of IQ may
have quite different mental abilities.
\
An IQ of 100 is considered average, and a 10-year-old child with a mental
age of 14 has an IQ of 140, well above average. With a mental age of 6, this same
child would have a below-average IQ of 60. The advantage of the IQ is that it can be
used to compare people of different ages. A 5-year-old child with a mental age of 7
also has an IQ of 140. Compared to peers, the 5-year-old child and 10-year-old child
are equally bright (Figure 14.5).
This method of obtaining the IQ, called the conventional method, has been
replaced in formal research and clinical work by the deviation method, which eliminates
certain statistical inconsistencies. It indicates the individual's score in terms of
deviation from the mean for a given age, rather than on an absolute basis, and it is
typically obtained by consulting prepared tables. Except for knowing the existence of
this newer method, you need not be overly concerned, for the deviation and conventional
IQs usually differ by less than three points.
The Wechsler Scales Some years later a group of psychologists in New York City
began to develop a test for adult intelligence, which also has been revised many times.
Now called the Wechsler Adult Intelligence Scale—Revised (WAIS-R), it is a popular
individual test for people from ages 16 to 74, and there are several counterparts for
testing children. The Wechsler and Binet scales together cover almost the full range
of human development (Evers & Zaal, 1982).
In contrast to the Stanford-Binet, the Wechsler items are grouped according
to the mental function involved, rather than age level. All of the items on perception,
for example, appear together in order of increasing difficulty. Each subject starts on
the simplest items of a given type and progresses to more difficult ones.
Since each subtest concerns a different function, the Wechsler provides an
overall measure of intelligence and also an indication of the individual's intellectual
style or profile. A person with a strong school background might perform well on the
subtests that concern general information, vocabulary, and numerical ability. A person
with much practical experience might succeed best in problem solving and cpmprehension.
Still another person might score highest in memory, perception, and motor
coordination. Each of these people has a distinct pattern of abilities, although all three
of them may function at the same overall level. The capacity to understand these differences
is a most important characteristic of the successful psychological examiner
(Figure 14.6).
One subtest alone is not a good measure of intelligence, as we know from
Galton's failure with lifted weights and from many psychiatric cases in which people
with astounding memory or mathematical ability are unable to read or manage a conversation.
The purpose of including a variety of tests is to sample as many aspects of
the individual's adjustment or versatility as possible, as Binet wisely advised. An intelligence
test is basically an efficient method of obtaining samples of behavior.
Validity of Intelligence Tests The value of intelligence tests has been controversial
since Binet's original efforts, for these tests have limitations. Some intelligence tests,
for example, are insensitive to damage in the frontal areas of the brain, yet these lobes
are associated with several higher mental functions. Traditional intelligence tests also
tend to require one particular response to each problem rather than several answers
or diverse approaches to the same problem. Such tests are therefore considered deficient
in measuring creativity. Often they emphasize verbal and numerical tasks, which may
be relatively unimportant outside school.
Intelligence tests sometimes have been criticized as a tool for social control,
promoting one kind of intelligence. Some courts on this basis have barred the testing
of intelligence in schools; there have been attacks on the Civil Service Examination;
and there have been charges of bias in personnel selection.