Unit 2 Essay

Prompt: Compare and contrast the Spearman and Thurston theories of intelligence

500-750+ words. Okay to go over on word count. MLA style. Please cite any additional sources

NOTE: BELOW IS A WORD FOR WORD QUOTE FROM THE PASSAGE OF TEXT CONCERNING THE PROMPT QUESTION.

Textbook: Hogan, T.P. Psychological Testing: A Practical Introduction, 3rd ed., Wiley Publishing Company, 2015

Text reads as follows…

Two Classical Theories

There are two classical theories of intelligence. They have dominated literature on the nature of intelligence.

Spearman’s “g”

Charles Spearman (1904, 1927a, 1927b), an Englishman, developed what is generally considered the first data-based theory about human mental ability.

Chapter 1 contained a brief description of this theory. Spearman based this theory. Spearman based his theory on examination of the correlations between many tests of simple sensory functions. He thought that these correlations were sufficiently high to conclude that performance on the tests was most dependent on one general mental ability. He called this general ability “g” (always lowercase g). Of course, the correlations among the various measures were not perfect. Each test had some unique or specific variance, independent of “g.” Thus, any set of tests had a series of “s” factors, and one “g” factor. Spearman also relegated error variance to the “s” factors. Hence, each “s” contained some variance unique to a specific ability plus error variance. However, many summaries of Spearman’s theory mention only “g” and “s.”

Figure 7.2 depicts Spearman’s theory. Each oval in the figure represents a test. The degree of overlap between the ovals represents the degree of correlation between them. The large area in the center corresponds to “g,” the general factor in mental ability. Each oval also has an area that does not overlap with other ovals. The areas of nonoverlap are the “s” factors, specific to that particular test.

Since the theory has two types of factors (“g” and a series of “s’s”), Spearman called it two-factor theory. However, the dominant factor in the theory is “g.” The “s’s” are not of much interest. Hence, despite Spearman’s use of the two-factor terminology, the theory is usually called a one-factor or unifactor theory of intelligence. Sometimes it is simply called the theory of “g.”

In the process of developing his theory of human intelligence, Spearman worked out the elements of factor analysis. We reviewed this statistical technique earlier (p. 183). By today’s standards, his methods were quite primitive. However, he showed remarkable insight regarding how to think about the relationship among many tests, thus pointing the way for a wide variety of applications in testing and other social sciences.

Spearman’s “g” remains a central concept in psychologists’ thinking about intelligence. It serves as a common reference point in the test manuals, as well as in other theories about intelligence. We should note that Spearman’s original works, though now dated in many respects, provide a rich source of insights for the modern student of psychology. Many contemporary summaries of Spearman’s work over simplify his thinking. For example, in addition to “g” is the central concept with the most enduring influence in the field.

Thurstone’s Primary Mental Abilities

Throughout the early years in the debate over the nature of intelligence, the American psychologist L.L. Thurstone, at the University of Chicago, provided the main competition to Spearman’s theory of “g.” Whereas Spearman said that the correlations among different tests were high enough to think that they were mostly measuring one common factor, Thurston (1938) believed that the correlations were low enough to think they were measuring several largely independent factors, thus yielding a multiple-factor theory. Figure 7.3 depicts Thurstone’s theory. As in the illustration of Spearman’s theory, the degree of overlap among the ovals represents the level of correlation. Thurstone emphasized the separation between ovals, whereas Spearman emphasized the overlap. Each of the “P’s” in Figure 7.2 is relatively independent factor. Like Spearman, in the process of developing his theory, Thurstone made major contributions to factor-analytic methodology. His books, The Vectors of the Mind (Thurstone, 1938), and especially its revision, Multiple-Factor Analysis (Thurstone, 1947), helped define modern factor analysis.

In his most famous study, Thurstone (1938) administered a battery of 60 tests (15 hours of testing!) to 240 students. (The sample was highly selective: all males and nearly all students at the University of Chicago.) Thurstone extracted twelve factors, nine of which he considered interpretable. He called these group factors or primary mental abilities. The latter term stuck. Table 7.2 lists the nine factors originally identified by Thurstone, with brief descriptions of each factor.

Interestingly, Thurstone was the only major theorist who authored mental ability tests that attained any widespread use. There were editions from different publishers and for different age levels. None of the tests is currently in use. Understandably, all the tests included the tag “primary mental abilities” (PMA), which we will use as a generic descriptor here. The various versions of the PMA test covered only five of the original nine factors—but not always the save five! Thus, there are many references in the literature to Thurstone’s five factors, but one easily becomes confused tyring to identify exactly what the five factors are. As summarized in Table 7.3, of the original nine factors, four factors appear in nearly all versions of PMA tests: spatial, numerical, verbal, and reasoning. The original factors induction, reasoning, and deduction collapse into a single reasoning factor. The perceptual, memory, and word fluency factors appear in some PMA tests but not in others, always bringing the total number of tests to five. Of these last three factors, the perceptual factor most frequently appeared as the fifth factor in a PMA test.

Thurstone was not the only person to propose a multifactor theory of intelligence. In what he called the structure of intellect model, J.P. Guilford (1956, 1959b, 1967, 1985, 1988) presented what is undoubtedly the most extreme version of a multifactor theory of intelligence. According to Guilford, mental ability manifests itself along three principles axes: contents, products, and operations. Each of these axes contains further subdivisions—five for content, six for products, and six for operations. The three axes may be depicted in the form of a cube, with the subdivisions forming cells, thus yielding 5 X 6 X 6 = 180 cells, which Guilford posited to be relatively independent of one another.

Guilford’s theory has not stood the test of time (and research). But one of the distinctions build into the model has endured, that is, the distinction between divergent production and convergent production. There were subdivisions along the operations axis. Divergent production involves producing alternative or unusual solutions. Convergent production involves identification of a single correct answer. That is, in convergent thinking, the mind converges on one answer. In divergent thinking, the mind diverges from the usual path to seek diverse possibilities. This reference to divergent thinking helped stimulate a great deal of research

Table 7.2

S Spatial                   Spatial, especially visual, ability, as in doing mental rotations of geometric figures or counting hidden blocks

P Perceptual               Perceptual, especially speed of visual perception, as in scanning a printed page to identify letters or comparing columns of numbers

N Numerical             Numerical, especially, speed and accuracy of computation

V Verbal                   Verbal, including verbal analogies, antonyms, reading comprehension

M Memory               Rote, short-term memory, as in paired-associate learning

W Words                   Word fluency, especially dealing with isolated words, as in the disarranged word test or word fluency test.

I Induction                 Finding a rule or principle to solve a problem, as in number series, figure classification, or pattern analogies

R Reasoning             Reasoning, especially when dealing with a closed-solution problem as in arithmetic reasoning.

D Deduction             A factor weakly defined by several tests calling for application of a rule.