Because so many primary mental abilities have been identified, some researchers think it may be easier to understand intellectual development by looking at interrelationships among them. Careful consideration of the relationships among the primary mental abilities has resulted in the identification of secondary mental abilities, which are broad­ranging skills, each composed of several primary abilities (Horn, 1982; Horn & Hofer, 1992). At pres­ent, at least six secondary abilities have been found. Each of these is described in Table 7.1. Most of the developmental research and discussion of these abilities has been focused on two: fluid intelligence and crystallized intelligence.

Fluid and Crystallized Intelligence. Crystallized and fluid intelligence include many of the basic abili­ties that we associate with intelligence, such as verbal comprehension, reasoning, integration, and
concept formation (Horn, 1982; Horn & Hofer,

1992) . Interestingly, they are associated with age differently, are influenced by different underlying variables, and are measured in different ways.

Fluid intelligence consists of the abilities that make you a flexible and adaptive thinker, that allow you to draw inferences, and that enable you to under­stand the relations among concepts independent of acquired knowledge and experience. It reflects the abilities you need to understand and respond to any situation, but especially new ones: inductive reasoning, integration, abstract thinking, and the like (Horn, 1982). Here is an example of a question that taps fluid abilities: “What letter comes next in the series d f i m r x e?”’

Other typical ways of testing fluid intelligence include mazes, puzzles, and relations among shapes.

1The next letter is m. The rule is to increase the difference between adjacent letters in the series by one each time. Thus, f is two letters away from d, i is three letters away from f, and so on.

Intelligence 243

Table 7.1

Descriptions of Major Second-Order Mental Abilities

Crystallized intelligence (Gc)

This form of intelligence is indicated by a very large number of performances indicating breadth of knowledge and experience, sophistication, comprehension of communications, judgment, understanding of conventions, and reasonable thinking. The factor that provides evidence of Gc is defined by primary abilities such as verbal comprehension, concept formation, logical reasoning, and general reasoning. Tests used to measure the ability include vocabulary (What is a word near in meaning to temerity?), esoteric analogies (Socrates is to

Aristotle as Sophocles is to __ ?), remote associations

(What word is associated with bathtub, prizefighting, and wedding?), and judgment (Determine why a foreman is not getting the best results from workers).

As measured, the factor is a fallible representation of the extent to which a person has incorporated, through the systematic influences of acculturation, the knowledge and sophistication that constitutes the intelligence of a culture.

Fluid intelligence (Gf)

The broad set of abilities of this intelligence includes those of seeing relationships between stimulus patterns, drawing inferences from relationships, and comprehending implications. The primary abilities that best represent the factor, as identified in completed research, include induction, figural flexibility, integration, and, cooperatively with Gc, logical reasoning and general reasoning. Tasks that measure the factor include letter series (What letter comes next in the series d f i m r x e?), matrices (Discern the relationships between elements of 3-by-3 matrices), and topology (From among a set of figures in which circles, squares, and triangles overlap in different ways, select a figure that will enable one to put a dot within a circle and a square but outside a triangle). The factor is a fallible representation of such fundamental features of mature human intelligence as reasoning, abstracting, and problem solving. In Gf these features are not imparted through the systematic influences of acculturation but instead are obtained through learning that is unique to an individual or is in other ways not organized by the culture.

Visual organization (Gv)

This dimension is indicated by primary mental abilities such as visualization, spatial orientation, speed of closure, and flexibility of closure, measured by tests such as gestalt closure (Identify a figure in which parts have been omitted), form board (Show how cutout parts fit together
to depict a particular figure), and embedded figures (Find a geometric figure within a set of intersecting lines). To distinguish this factor from Gf, it is important that relationships between visual patterns be clearly manifest so performances reflect primarily fluency in perception of these patterns, not reasoning in inferring the process.

Auditory organization (Ga)

This factor has been identified on the basis of several studies in which primary mental abilities of temporal tracking, auditory cognition of relations, and speech perception under distraction of distortion were first defined among other primary abilities and then found to indicate a broad dimension at the second order. Tasks that measure Ga include repeated tones (Identify the first occurrence of a tone when it occurs several times), tonal series (Indicate which tone comes next in an orderly series of tones), and cafeteria noise (Identify a word amid a din of surrounding noise). Like Gv, this ability is best indicated when the relationships among stimuli are not such that one needs to reason for understanding but instead are such that one can fluently perceive patterns among the stimuli.

Short-term acquisition and retrieval

This ability comprises processes of becoming aware and processes of retaining information long enough to do something with it. Almost all tasks that involve short-term memory have variance in this factor. Span memory, associative memory, and meaningful memory are primary abilities that define the factor, but measures of primary and secondary memory can also be used to indicate the dimension.

Long-term storage and retrieval

Formerly this dimension was regarded as a broad factor among fluency tasks, such as those of the primary abilities called associational fluency, expressional fluency, and object flexibility. In recent work, however, these performances have been found to align with others indicating facility in storing information and retrieving information that was acquired in the distant past. It seems, therefore, that the dimension mainly represents processes for forming encoding associations for long-term storage and using these associations, or forming new ones, at the time of retrieval. These associations are not so much correct as they are possible and useful; to associate teakettle with mother is not to arrive at a truth so much as it is to regard both concepts as sharing common attributes (e. g., warmth).

Such tests are usually timed, and higher scores are associated with faster solutions.

Crystallized intelligence is the knowledge that you have acquired through life experience and edu­cation in a particular culture. Crystallized inte­lligence includes your breadth of knowledge, comprehension of communication, judgment, and sophistication with information (Horn, 1982). Your ability to remember historical facts, defini­tions of words, knowledge of literature, and sports trivia i nformation are some examples. Many popu­lar television game shows (such as “Jeopardy” and “Wheel of Fortune”) are based on tests of contestants’ crystallized intelligence. However, even though crys­tallized intelligence involves cultural knowledge, it is based partly on the quality of a person’s underlying fluid intelligence (Horn, 1982; Horn & Hofer, 1992). For example, the breadth of your vocabulary depends
to some extent on how quickly you can make con­nections between new words you read and informa­tion already known, which is a component of fluid intelligence.

Any standardized intelligence test taps abilities underlying both fluid and crystallized intelligence. No single test of either ability exists, because each represents a cluster of underlying primary abilities. As a general rule, tests that minimize the role of acquired, cultural knowledge involve mainly fluid intelligence; those that maximize the role of such knowledge involve mainly crystallized intelligence.

Developmentally, fluid and crystallized intelli­gence follow two very different paths, similar to the individual primary abilities characterized by the pragmatics and mechanics of intelligence. This pat­tern is depicted in Figure 7.4. Notice that fluid intel­ligence declines significantly throughout adulthood,

whereas crystallized intelligence improves. Although we do not fully understand why fluid intelligence declines, it may be related to underlying changes in the brain from the accumulated effects of disease, injury, and aging or from lack of practice (Horn & Hofer, 1992). In contrast, the increase in crystallized intelligence (at least until late life) indicates that people continue adding knowledge every day.

What do these different developmental trends imply? First, they indicate that although learning continues across adulthood, it becomes more dif­ficult the older one gets. Consider what happens when Michele, age 17, and Marion, age 70, try to learn a second language. Although Marion’s verbal skills in her native language (a component of crystal­lized intelligence) are probably better than Michele’s verbal skills, Michele’s probable superiority in the fluid abilities necessary to learn another language will usually make it easier for her to do so.

Second, these developmental trends point out once again that intellectual development varies a great deal from one set of skills to another. Beyond the differences in overall trends, individual differ­ences in fluid and crystallized intelligence also exist. Whereas individual differences in fluid intelligence remain relatively uniform over time, individual differences in crystallized intelligence increase or remain stable with age, largely because maintain­ing one’s crystallized intelligence depends on being in situations that require one to use it (Finkel et al., 2003; Horn & Hofer, 1992). For example, few adults get much practice in solving complex letter series tasks such as the one described earlier. But because people can improve their vocabulary skills by reading, and because people vary considerably in how much they read, differences are likely to emerge. In short, crystallized intelligence provides a rich knowledge base to draw on when mate­rial is somewhat familiar, whereas fluid intelligence provides the power to deal with learning in novel situations.