Does the Shipley Institute of Living Scale Measure Fluid and Crystallized Abilities?

Article excerpt

Developed over six decades ago, the Shipley Institute of Living Scale (Shipley, 1967; Zachary, 1991) is a brief measure of intelligence consisting of two subtests. On the Abstraction subtest, participants must complete numerical problems, word patterns, and analogies for 20 different problems, and on the Verbal subtest, participants must choose synonyms for 40 English words that become increasingly more difficult. The test usually takes less than 20 minutes to administer and yields raw scores that can be converted to standard IQ scores (Zachary, 1991).

While the Shipley enjoys status as a well-established brief measure of intelligence, the test was not developed from a theoretically based model of intelligence. The Abstraction and Verbal subtests of the Shipley, however, appear to measure constructs similar to the fluid and crystallized abilities first purported by Horn and Cattell (Cattell, 1941, 1963; Horn & Cattell, 1966) and later by Carroll and other researchers (Carroll, 1993; Horn & Noll, 1997). Indeed, the Shipley manual (Zachary, 1991) describes the Abstraction scale as tapping attention and problem solving processes that are more fluid in nature, while the Shipley Verbal scale is easily conceptualized as a test of crystallized ability due to its verbal content. Although the psychometric properties of the Shipley have been supported by research, the fact remains that the Shipley does not operate from an established theoretical base.

The Cattell-Horn-Carroll (Carroll, 1993; Horn & Noll, 1997) theory of fluid and crystallized intelligence maintains its status as one of the current major empirical theories of intelligence. This paradigm conceptualizes intelligence as composed of many subcomponents, with two major components being fluid (Gf) and crystallized (Gc) abilities. The Cattell-Horn-Carroll theory's concept of fluid intelligence, or Gf, represents pure, nonverbal mental efficiency that is less influenced by cultural or educational experience. Individuals may demonstrate fluid intelligence through completion of figure classifications, figural analyses, number and letter series, matrices and paired associates (Sattler, 1992). The items on the Shipley Abstraction scale purport to measure these same constructs. To complete the word and number puzzles, the examinee merely needs to know how to read, count, and relate simple words and numbers; abilities that reflect minimal cultural and educational bias. Conversely, the theory postulates that crystallized intelligence, or Gc, encompasses acquired skills and knowledge that depend on educational exposure. This dimension of intelligence may also be culturally sensitive. Crystallized abilities may be measured by performance on such tasks as: vocabulary, abstract word analogies, and mechanics of language (McGrew, 1997). The vocabulary words in the Shipley's Verbal section require a participant to have learned the words on the test prior to taking it; a task rooted in educational and cultural experience. The current study attempts to compare the Shipley Abstraction and Verbal subscales to the KAIT Gf and Gc components to determine if the Shipley does in fact measure similar constructs as the KAIT.

Validity of the KAIT

Kaufman and Kaufman (1993) purport to measure crystallized and fluid abilities with the KAIT. This theoretically based test contains four subtests designed to measure fluid abilities: Rebus Learning, Logical Steps, Mystery Codes and Memory for Block Designs. Four subtests also measure Crystallized ability: Definitions, Auditory Comprehension, Double Meanings, and Famous Faces. The KAIT Fluid subtests contain numerous symbols, abstract designs, and problem solving items that tap into pure reasoning abilities that operate autonomously from educational placement or achievement. The KAIT Crystallized subtests include vocabulary words, short story comprehension and pictures of historic and popular icons that measure a participant's accumulation of knowledge over time. …