One thing is clear about the ways people view intelligence—everyone considers it a complex con­struct. In the big picture, then, intelligence consists
of many different types of skills. Theories of intel­ligence, therefore, are multidimensional; that is, they specify many domains of intellectual abilities. Although people disagree on the number of dimen­sions, they do agree that no single generic type of intelligence is responsible for all the different kinds of mental activities we perform.

Baltes and colleagues (Baltes, 1993; Baltes et al.,

1999) take a broad view of intellectual develop­ment. The life-span concepts discussed in Chapter 1 including multidirectionality, plasticity, and inter­individual variability play an important role in this conceptualization of intellectual change. Overall, this perspective asserts that some intellectual decline may be seen with age but that stability and growth in mental functioning also can be seen across adult­hood. It emphasizes the role of intelligence in human adaptation and daily activity.

The first concept, multidirectionality, refers to the distinct patterns of change in abilities over the life span, with these patterns differing for different abilities. For example, developmental functions for specific abilities differ, meaning that the directional

change in intelligence depends on the skills in ques­tion. As you will see later on, everyday knowledge accumulates over time and thus increases with age. However, basic cognitive mechanisms show more declines, especially into older age.

The term plasticity refers to the range of function­ing within an individual and the conditions under which a person’s abilities can be modified within a specific age range. Plasticity implies that what may appear to be declines in some skills may in part represent a lack of practice in using them. Current studies examining brain plasticity and behavior find that experience alters the brain across the life span (see Chapter 2). For example, Patty Reuter-Lorenz (2002; Reuter-Lorenz & Mikels, 2006) found that older and young adults show different activation patterns in the brain when they perform cognitive tasks. Furthermore, older adults seem to activate areas in the brain that compensate for decline in their performance, resulting in optimal perfor­mance. In other words, older adults may activate new areas in the brain to compensate for decline in other areas. Finally, the research on training cog­nitive abilities described later in this chapter also supports this view in that older adults who show decline in cognitive functioning can be trained to perform at a higher level.

The last concept, interindividual variability, acknowledges that adults differ in the direction of their intellectual development (MacDonald, Hultsch, & Dixon, 2003; Schaie, 2008). Schaie’s sequential research indicates that within a given cohort or generation some people show longitudinal decline in specific abilities, whereas some people show sta­bility of functioning in those same abilities. Finally, others show increments in performance in those same abilities (Schaie, 2008). Consequently, a curve representing typical or average changes with age may not really represent how the various individu­als in a group function.

Using these four concepts of multidimensional­ity, plasticity, multidirectionality, and interindivid­ual variability, Baltes and his colleagues proposed the dual-component model of intellectual func­tioning. Two interrelated types of developmen­tal processes are postulated. The first component, termed the mechanics of intelligence, concerns the neurophysiological architecture of the mind (Baltes et al., 1999; Li et al., 2004). Cognitive abilities include basic forms of thinking associated with information processing and problem solving such as reasoning, spatial orientation, or perceptual speed. Intellectual change in this first component is greatest during childhood and adolescence, as we acquire the requisite skills to handle com­plex cognitive tasks, such as those encountered in school. The second component, pragmatic intel­ligence, concerns acquired bodies of knowledge available from and embedded within culture. In other words, it includes everyday cognitive per­formance and human adaptation. Such abilities include verbal knowledge, wisdom, and practi­cal problem solving. Pragmatic intellectual growth dominates adulthood.

These different trajectories of development are illustrated in Figure 7.1. As the figure suggests, dif­ferent weightings of the forces of intelligence lead to specific predictions regarding the developmen­tal pathway they take across the adult life span. If biological-genetic forces are considered to govern the mechanics more, a downward trajectory appears with age. However, if the pragmatics of intelligence is considered to be governed more by environmental – cultural factors, an upward trajectory is maintained across the adult life span.

This broad view of intellectual development in adulthood provides the background for asking more specific questions about particular aspects of intelligence. As we will see, three primary research approaches have emerged.

Research Approaches to Intelligence

Sternberg’s work points out that many different skills are involved in intelligence, depending on one’s point of view. Interestingly, the behaviors listed by Sternberg’s participants fit nicely with the more formal attempts at defining intelligence that we will encounter in this chapter. Researchers have stud­ied these skills from many different perspectives, depending on their theoretical orientation. For example, some investigators approach these skills from a factor analysis approach and study them as

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Source: Reprinted with permission from Baltes, P. B., Staudinger, U. M., & Lindenberger, U. (1999). Lifespan psychology: Theory and application to intellectual functioning. Annual Review of Psychology 50, 487. Copyright © 1999 by Annual Reviews. www. annualreviews. org

separate pieces that can be added together to form intelligence. Others take a more holistic view and think of intelligence as a way or mode of thinking. These various theoretical orientations result in very different means of studying intelligence.

Some investigators, such as Schaie and Horn, have concentrated on measuring intelligence as per­formance on standardized tests; this view repre­sents the psychometric approach. For example, the problem-solving and verbal abilities in Sternberg and co-workers’ study would be assessed by tests specifi­cally designed to assess these skills. These tests focus on getting correct answers and tend to give less emphasis on the thought processes used to arrive at them. Other researchers, such as Salthouse and Craik, focus on information-processing mecha­nisms reviewed in Chapter 6. This approach aims at a detailed analysis of aging-associated changes in components of cognitive mechanisms and their interactions. Finally, a number of researchers have focused their efforts on reconceptualizing the mean­ing and measurement of intelligence by taking a cognitive-structural approach. In the cognitive – structural approach researchers have been more concerned with the ways in which people concep­tualize and solve problems than with scores on tests. Such approaches to intelligence empha­size developmental changes in the modes and

styles of thinking. These include a search for post­formal operations (e. g., Labouvie-Vief, 1992; Sin – nott, 1996), the assessment of wisdom (e. g., Baltes et al., 1995; Baltes & Kunzmann, 2003; Mickler & Staudinger, 2008), and studies of practical intelli­gence (e. g., Allaire & Marsiske, 2002; Bosworth & Ayotte, 2009; Marsiske & Willis, 1995). The age dif­ferences Sternberg found in which abilities their re­spondents believed were important correspond to the qualitative changes discussed by these theorists.

In this chapter, we will consider these theories and the research they stimulated. We will discover that each approach has its merits and that whether age – related changes in intelligence are found depends on how intelligence is defined and measured. But before you continue, complete the exercise in the Discovering Development feature. The information you uncover will be useful as you read the rest of the chapter.

Concept Checks

1. What three clusters of ability did Sternberg and colleagues identify in their study of people’s everyday conceptualizations of intelligence?

2. What are the four major aspects of intelligence emphasized by the life-span approach?

3. What are the three major approaches for researching intelligence?

How Do People Show Intelligence?

Earlier in this section, we encountered Sternberg and colleagues’ research on people’s implicit theories of intelligence. However, that study only examined broad categories of behavior that could be considered intelligent. Moreover, it was not conducted in such a way as to permit comparisons with research-based approaches to intelligence.

You and your classmates could address these shortcomings in the following way. Ask adults of different ages what they think constitutes intelligent behavior, much the same as Sternberg and colleagues did. However, be careful to make sure people are specific about the abilities they nominate. In addition, ask them about what makes adults’ thinking different from adolescents’ thinking and
whether they believe there might be different stages of adults’ thinking. Again, try to get your respondents to be as specific as possible.

Collate all the data from the class. Look for common themes in specific abilities, as well as in the qualitative aspects of thinking. As you read the rest of the chapter, see to what extent your data parallels that from more formal investigations.

7.2 Developmental Trends in Psychometric Intelligence


• What are primary mental abilities? How do they change across adulthood?

• What are secondary mental abilities? What are the developmental trends for fluid and crystallized intelligence?

• What are the primary moderators of intellectual change?

• How successful are attempts at training primary mental abilities?


inda and Jerry have recently retired. They are delighted with the prospect of engaging in activi­ties they did not have time for in the past because of work and child-rearing responsibilities. They have both enrolled in courses at the local community col­lege, to pursue their mutual interests in English lit­erature. After the first day of class, they both revealed that they were worried about being able to keep up with the younger students and wondered if they were smart enough. They both shrugged their shoulders and realized they would find out soon enough.

Many older adults like Linda and Jerry who are returning to a learning environment worry that they may not be “smart enough” to keep up with 18- or 19-year-olds. Are these fears realistic? Extensive evidence taking a psychometric approach describes how intellectual performance changes through the latter half of the life span.

One way to psychometrically measure intel­ligence is to focus on individuals’ performances on various tests of intellectual abilities and on how these performances are interrelated. This approach to intelligence has a long history; the ancient Chinese and Greeks used this method to select people for certain jobs, such as master horseman (Doyle, 1974; DuBois, 1968). It also served as the basis for Binet’s (1903) pioneering work in develop­ing standardized intelligence tests, as well as many modern theories of intelligence.

Because of this long history of research in psy­chometric intelligence, we probably know more about this area than any other area in cognitive aging except for episodic memory. Yet this still has provided no sense of closure as to how intelligence changes with age. There is substantial agreement on descriptions of change in different intellectual

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abilities (as we will discuss later) and agreement on the methodological issues that need to be addressed when studying intellectual change. However, there is little convergence on the proper interpretation of the data. For example, what does it mean that changes in intellectual abilities are related to increas­ing age? Remember in Chapter 1 we noted that age does not cause change. That age is related to intel­lectual abilities is not the same thing as “aging” per se. As we shall see, age-graded intellectual change is also related to important variables such as health, activity level, and educational achievements. It is in these areas that much of the controversy is still brewing.