Some psychologists view intelligence as a general capacity for comprehension and reasoning that manifests itself in various ways. This was Binet’s assumption, although, his test contained many different types of item, they were all assumed to tap general intelligence.

Other psychologists see intelligence an array of special abilities that tend to be positively correlated; they use the statistical method of factor analysis to provide more precise information about the abilities underlying intelligence.

As noted in the previous chapter, factor analysis is a technique for determining the minimum number of dimensions, or factors, that account for the observed relations (correlations) among subjects’ responses over a large number of different tests. The method is too intricate to describe in any detail here, but Table gives some understanding of what factor analysis tries to accomplish.

The originator of factor analysis, Charles Spearman, proposed that all individuals possess a general intelligence factor (called g) in varying amounts. A person would be described as generally bright or generally dull depending upon the amount of g. According to Spearman, the g factor is the major determination of performance on intelligence test items. In addition, special factors called s’s are specific to particular abilities or test items. For example, tests of arithmetic or spatial relations would each tap a separate.

ADVERTISEMENTS:

An individual’s tested intelligence reflects are amount of g plus the magnitude of the various s factors. Performance in mathematics would be a function of a person’s general intelligence and mathematical aptitude.

Primary Abilities :

A later investigator, Louis Thustone (1938), objected to Spearman’s emphasis on general intelligence, he felt that intelligence cold is broken down into a number of primay abilities to find these abilities he applied the method of factor analysis to results from a large number of tests employing many different types of items. One set of items was for verbal comprehension, another for arithmetical computation and so on.

He wished to find a more definitive way of grouping intelligence test items than the rather crude item-sorting used in the verbal and performance scales of the stanford-Binet and Wechsler tests.

ADVERTISEMENTS:

After inter correlation the scores of all the tests, Thurstone applied factor analysis to arrive at the basic factors. Those test items that best represented each of the discovered factors were used to from new tests; these tests were then given to another group of subjects and the inter correlations reanalyzed. After a number of studies of this kind, Thurstone identified the seven factors, shown in Table, as the primary abilities revealed by intelligence tests.

Ability

Description

Verbal comprehension

The ability to understand the meaning of words; vocabulary tests represent this factor.

Word fluency

The ability to think of words rapidly, as in solving anagrams or thinking of words that rhyme

Number

The ability to work with numbers and perform computations

Space

The ability to visualize space-from relationships, as in recognizing the same figure presented in different orientations.

Memory

The ability to recall verbal stimuli such as word pairs of sentences

Perceptual speed

The ability to grasp visual details quickly and to see similarities and differences between pictured objects

Reasoning

The ability to find a general rule on the basis of presented instances, as in determining how a number series a constructed after being presented with only a portion of that series.

Thurstone devised a battery of tests to measure each of these abilities, called the Test of Primary Abilities, which is still widely used. Its predictive power, however, is no greater than that provided by tests of general intelligence such as the Wechster Scales. Thurstone’s hope of discovering the basic elements of intelligence through factor analysis was not fully realized for several reasons.

His primary abilities are not completely independent; there are significant inter correlations among them providing some support for Spearman’s idea of a general intelligence factor. In addition, the number of factors identified by factor analysis depends on the nature of the test items chosen.

ADVERTISEMENTS:

Other investigators using different test items have come up with a larger number of factors. Guilford (1967), for example, has suggested that there are at least 120 unique intellectual abilities.