Abnormal Psychology

Childhood Disorders 627

range may be able to function relatively independently with training

but usually need additional help and support during stressful periods.

• Moderate mental retardation. The IQ score can range from 35–40

to 50–55; 10% of people with mental retardation fall into this

group. Although they are not able to function independently, with

training and supervision, people in this group may be able to per-

form unskilled work and take basic care of themselves.

• Severe mental retardation. The IQ score can range from 20–25 to

35–40; approximately 3–4% of people with mental retardation fall

into this group. Adults in this group are likely to live with their

family or in a supervised setting and are able to perform simple

tasks only with close supervision. They may be able to learn to

read a few basic words and do simple counting. During childhood,

they may begin speaking later than other children.

• Profound mental retardation. The IQ score falls below 20 or 25; 1–2% of those

with mental retardation fall into this group. People in this group need constant

supervision or help to perform simple tasks; they are likely to have signifi cant

neurological problems.

Figure 14.1 illustrates the IQ scores associated with the four levels of mental

retardation.

Although an individual’s IQ score serves as a guide, the most important criterion

for determining the level of mental retardation is the level of adaptive functioning

(Criterion B), which indicates how well the person can cope with life’s daily demands

compared to others of the same age and cultural background. Information from

parents and teachers may help the clinician to determine the individual’s ability to

function. Depending on IQ and level of adaptive functioning, someone with mental

retardation may require anywhere from minimal supervision to constant care. Many,

like Larry in Case 14.1, have needs and abilities that fall somewhere in the middle.

CASE 14.1 • FROM THE OUTSIDE: Mental Retardation

Larry, a 34-year-old man with moderate mental retardation... had been referred for com-

plaints of seeing “monsters,” “scary faces,” and “the bogeyman.” He initially appeared para-

noid and delusional, describing the feared bogeyman in detail. An assessment of possible

neurochemical or physical factors that might help explain the recent onset of these symp-

toms yielded no signifi cant diagnostic information....

Larry’s perception of monsters was specifi c to certain situations, such as being alone in a

dark room....

Specifi cally, when asked to go alone to any dark place [including the dark stairwell in his

group home, where Larry must go to carry out his assigned chore of taking down the trash],

he became agitated, resisted, and made loud statements about monsters and scary faces....

Larry’s monsters could be attributed to his limited means of communicating his fear of

being alone in the dark. [It appears, then, that Larry has a phobic response to the dark.]...

Even if the residence staff excused him from this task, Larry would remain agitated because

he believed he was shirking an important responsibility.

(Nezu, Nezu, & Gill-Weiss, 1992, pp. 78, 164)

14.1 • The Four Levels of

Mental Retardation There are

four levels of mental retardation, each

of which corresponds to a range of IQ

scores. As the graph indicates, most

people with mental retardation fall

in the mild range, with increasingly

smaller numbers of people having

more severe retardation.

Figure 14.1

141 Thh F L ll ff

g 4

Percentage of mentally impaired population

IQ score

90

100

80

70

10

20

30

40

50

60

0

0–20 20–35 35–50 50–70

Profound

mental

retardation

Severe

mental

retardation

Moderate

mental

retardation

Mild

mental

retardation

Note: The high-end cutoff for profound,

severe, and moderate mental retardation

can be 5 IQ points higher than noted in

this graph if the individual has a low

level of functioning for that IQ score.

Like Sean Penn’s character in the movie I Am Sam,

people with mild mental retardation can, with

training, learn to function independently. In this

scene Penn is shown with Michelle Pfeiffer, who

plays his lawyer in his fi ght to retain custody of

his young daughter.

New Line Cinema/Courtesy Everett Collection

Larry had two disorders: mental retardation and a specifi c phobia. Because of

his mental retardation, he had diffi culty explaining his fears. He received CBT treat-

ment for his phobia, which was successful, and he became able to go down to the

basement without fear.

Like people of normal intelligence, people with mental retardation exhibit a wide

variety of personality characteristics: Some are passive or easygoing, and others are

impulsive or aggressive; those who have severe or profound mental retardation—or

even moderate mental retardation, like Larry—may have diffi culty communicating