Cognitive Changes

377
Adulthood
heart disease sometimes result from problems of diet—too little fluid, too little fiber,
too much fat—and inactivity. In addition, the brain shrinks during late adulthood. The
few reflexes that remained after infancy, such as the knee-jerk reflex, weaken or disappear. The flow of blood to the brain slows. As in earlier years, many of these changes
can be delayed or diminished by a healthy diet and exercise (Brach et al., 2003; Larson
et al., 2006; Seeman & Chen, 2002).
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Intelligence
Cognitive Changes
Adulthood is marked by increases, as well as decreases, in cognitive abilities. Abilities that
involve intensive information processing begin to decline in early adulthood, but those
that depend on accumulated knowledge and experience increase until beginning to tail
off in old age, if at all. In fact, older adults may function as well as, or better than, younger
adults in situations that tap their long-term memories and well-learned skills (Park et al.,
2002; Park & Gutchess, 2006). The experienced teacher may deal with an unruly child
more skillfully than the new teacher, and the senior lawyer may understand the implications of a new law better than the recent graduate. Their years of accumulating and organizing information can make older adults practiced, skillful, and wise.
Early and Middle Adulthood Until age sixty at least, important cognitive abili-
ties improve. During this period, adults do better on tests of vocabulary, comprehension, and general knowledge—especially if they use these abilities in their daily lives or
engage in enriching activities such as travel or reading (Park, 2001). Young and middleaged adults learn new information and new skills; they remember old information and
hone old skills. In fact, it is in their forties through their early sixties that people tend
to put in the best performance of their lives on complex mental tasks such as reasoning, verbal memory, and vocabulary (Willis & Schaie, 1999).
The nature of thought may also change during adulthood. Adult thought is often
more complex and adaptive than adolescent thought (Labouvie-Vief, 1992). Unlike
adolescents, adults see both the possibilities and the problems in every course of
action—in deciding whether to start a new business, back a political candidate, move
to a new place, or change jobs. Middle-aged adults are more expert than adolescents
or young adults at making rational decisions and at relating logic and abstractions to
actions, emotions, social issues, and personal relationships (Tversky & Kahneman,
1981). As they appreciate these relationships, their thought becomes more global, more
concerned with broad moral and practical issues (Labouvie-Vief, 1982). It has been suggested that the achievement of these new kinds of thinking reflects a stage of cognitive
development that goes beyond Piaget’s formal operational period (Lutz & Sternberg,
1999). In this stage, people’s thinking becomes dialectical, which means they understand that knowledge is relative, not absolute—such that what is seen as wise today may
have been thought foolish in times past. They see life’s contradictions as an inevitable
part of reality, and they tend to weigh various solutions to problems rather than just
accepting the first one that springs to mind.
Late Adulthood It is not until late in adulthood, after the age of sixty-five or so,
that some intellectual abilities decline noticeably. Generally, these are abilities that
require rapid and flexible manipulation of ideas and symbols, active thinking and reasoning, and sheer mental effort (Baltes, 1993, 1994; Finkel et al., 2003; see Figure 9.8).
Older adults do just as well as younger ones at tasks they know well, such as naming
familiar objects (Radvansky, 1999). However, when asked to perform an unfamiliar task
or to solve a complex problem they have not seen before, older adults are generally
slower and less effective than younger ones (Craik & Rabinowitz, 1984). When faced
with complex problems, older people apparently suffer from having too much information to sift through. They have trouble considering, choosing, and executing solutions (Arenberg, 1982). As people age, they grow less efficient at organizing the elements of a problem and at holding and mentally manipulating more than one idea at
a time. They have difficulty doing tasks that require them to divide their attention
378
Chapter 9
FIGURE 9 .8
Mental Abilities over the
Life Span
70
65
60
55
T score
Mental abilities collectively known as
“fluid” intelligence—speed and accuracy
of information processing, for example—
begin to decline quite early in adult life.
Changes in these biologically based aspects of thinking are usually not noticeable until late adulthood, however.
“Crystallized” abilities learned over a lifetime—such as reading, writing, comprehension of language, and professional
skills—decline too, but later and at a
slower pace (Li et al., 2004).
Human Development
50
45
40
35
30
25
10
20
30
40
50
60
70
80
90
Age
Crystallized intelligence
Fluid intelligence
Source: Adapted from Baltes (1994).
between two activities and are slower at shifting their attention back and forth between
those activities (Smith et al., 2001; Wecker et al., 2005). If older adults have enough
time, though, and can separate the two activities, they can perform just as well as
younger adults (Hawkins, Kramer, & Capaldi, 1993).
Usually, the loss of intellectual abilities is slow and need not cause severe problems
(Bashore & Ridderinkhof, 2002). A study of older adults in Sweden (Nilsson, 1996)
showed, for example, that their memory problems were largely confined to episodic
memory (e.g., remembering what they had for lunch yesterday) rather than semantic
memory (remembering general information, such as the capital of Italy). In other
words, everyday abilities that involve verbal processes are likely to remain intact into
advanced old age (Freedman, Aykan, & Martin, 2001).
The risk of cognitive decline is significantly lower for people who are healthy and
psychologically flexible and who have a high level of education, income, and occupation. Environmental factors are important, too (Reynolds et al., 2005). Cognitive decline
is slower among those who live in an intellectually stimulating atmosphere with mentally able spouses or companions (Albert et al., 1995; Chodosh et al., 2002; Shimamura
et al., 1995). Continued mental exercise—such as doing puzzles, painting, and having
intellectually stimulating conversations with friends—can also help older adults think
and remember effectively and creatively (Verghese et al., 2003, 2006; Wilson, Beckett,
et al., 2002). Practice at memory and other information-processing tasks may even lead
to some improvement in skills already impaired by old age and disuse (Kramer & Willis,
2002; Rapp, Brenes, & Marsh, 2002). Maintaining physical fitness through dancing or
other forms of aerobic exercise has been associated with better maintenance of skills
on a variety of mental tasks, including those involving reaction time, reasoning, and
divided attention (Abbott et al., 2004; McAuley, Kramer, & Colcombe, 2004; Weuve
et al., 2004). And a life full of organized activities and opportunities to interact with a
lots of different people—not just family members—seems best for preventing decline
in communication abilities (Keller-Cohen et al., 2004).
The greatest threat to cognitive abilities in late adulthood is Alzheimer’s disease. As
the disease progresses, it leaves even the brightest minds incapable. Victims become
emotionally flat, then disoriented, then mentally vacant. They usually die prematurely.
The average duration of the disease, from onset to death, is seven years. But the age
of onset and rate of decline depends on a number of factors, such as intelligence
(Rentz et al., 2004), gender (Molsa, Marttila, & Rinne, 1995), and education (Mortimer,
Snowdon, & Markesbery, 2003). Highly intelligent people show clinical signs of
Alzheimer’s later than the general population. Women and well-educated people of
either gender deteriorate more slowly.