Abnormal Psychology

Cognitive Disorders 683

and these must be taken into account when attempting to determine whether an

older individual has a disorder. Thus, the neuropsychologist must assess whether

Mrs. B.’s functioning has declined and, if so, whether this decline is beyond what

occurs with the normal aging process. In this section, we examine what happens to

cognitive functioning during normal aging and then examine the neurological fac-

tors that can disrupt cognitive functioning.

Cognitive Functioning in Normal Aging

Most—though not all—aspects of cognitive functioning remain relatively stable

during older adulthood. Let’s fi rst examine intelligence, which can be divided into

two sets of abilities, or types of intelligence (Cattell, 1971): Crystallized intelligence

relies on using knowledge to reason; such knowledge has “crystallized” from previ-

ous experience. Normally, crystallized intelligence, such as the ability to understand

what various words mean, remains stable or increases with age, even among older

adults; crystallized intelligence is often assessed through tests that measure verbal

ability, and these tests often allow ample time for people to respond to questions. In

contrast,fl uid intelligence relies on the ability to create new strategies to solve new

problems, without relying solely on information previously learned. Fluid intelli-

gence relies on executive functions, which include the abilities to think abstractly, to

plan, and to exert good judgment. Fluid intelligence is typically assessed with tests

of visual-motor skills, problem solving, and perceptual speed (Salthouse, 2005);

these tests usually are timed, and points are lost for taking “too long” to respond

with the right answer. If Mrs. B. took such tests, even if she gave the correct answer,

her scores would be lower if she took more than a “normal” amount of time. As

adults age, they respond more slowly, and so their scores on most measures of fl uid

intelligence decline. Specifi cally, these kinds of test scores begin to decline notice-

ably at around age 55, with a more signifi cant decline at around age 65 (Harvey,

2005a). When tests are not timed, however, the decline in fl uid intelligence is

lesspronounced, particularly on tests that involve executive functioning (Jennings

et al., 2007).

Of course, normal cognitive decline is always judged in relation to the indi-

vidual’s baseline. An older adult who starts out with a high IQ and has functioned

well will probably be able to continue to function well even with the normal de-

cline of aging. In contrast, the functioning of someone who has a lower IQ initially

(such as in the low normal range, or an IQ of 85 or lower) will be affected more

dramatically—perhaps to the point where his or her ability to function indepen-

dently is curtailed (Harvey, 2005a).

Let’s examine in more detail some of the specifi c mental processes that are affected

by normal aging: memory, processing speed, attention, and executive functions.

Memory

Memory is not a single ability, and various aspects of it are affected in different

ways by aging. We can distinguish between implicit and explicit memories. Implicit

memoriesconsist of unconscious stored information that guides a person to behave

in certain ways. Classical and operant conditioning produce implicit memories; hab-

its, such as those used by someone who is adept at cooking or trout fi shing, are im-

plicit memories. Implicit memories are not affected very much by aging (Fleischman

et al., 2004). Older people often remember how to perform well-learned tasks such

as driving or typing.

In contrast, explicit memories can be voluntarily brought to mind, as words or

mental images. For example, remembering where you left your house keys, the name

of your best friend, or the facts you learned earlier in this book relies on explicit

memories. The elderly (generally considered to be people aged 65 and older; World

Health Organization [WHO], 2009) tend to have problems with some aspects of

explicit memories. In particular, they have problems in recalling stored explicit in-

formation. To recall information is to activate that information after voluntarily

Aging normally only minimally affects crystal-

lized intelligence, which relies on knowledge

based on previous experience.

Rick Gomez/Corbis

Crystallized intelligence

A type of intelligence that relies on using

knowledge to reason; such knowledge has

“crystallized” from previous experience.

Fluid intelligence

A type of intelligence that relies on the

ability to create new strategies to solve

new problems, without relying solely on

information previously learned.