Understanding Psychology (10th Ed)

retardation
( or  intellectual disability  ) is a disability characterized by signifi cant 
limitations both in intellectual functioning and in conceptual, social, and practical 
adaptive skills (AAMR, 2002). (Although experts are increasingly using the term 
intellectual disability instead of mental retardation , our discussion will use the original 
term because it continues to be more widespread.)
Although below-average intellectual functioning can be measured in a rela-
tively straightforward manner—using standard IQ tests—it is more diffi cult to 
determine how to gauge limitations in adaptive behavior. Consequently, there is a 
lack of uniformity in how experts apply the labels mental retardation and intellectual 
disabilities . People labeled mentally retarded vary from those who can be taught to 
mental retardation (or intellectual 
disability)
A condition characterized 
by signifi cant limitations both in 
intellectual functioning and in 
conceptual, social, and practical 
adaptive skills.
Key Concepts 
How are the extremes of 
intelligence characterized? 
How can we help people 
reach their full potential?
M O D U L E 2 7 
Variations in Intellectual Ability 
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296 Chapter 
9 
Intelligence
work and function with little special attention to those who cannot be trained and 
are institutionalized throughout their lives (Detterman, Gabriel, & Ruthsatz, 2000; 
Greenspan, 2006). 
Most people with mental retardation have relatively minor defi cits and are clas-
sifi ed as having mild retardation . These individuals, who have IQ scores ranging from 
55 to 69, constitute some 90% of all people with mental retardation. Although their 
development is typically slower than that of their peers, they can function quite 
independently by adulthood and are able to hold jobs and have families of their own 
(Bates et al., 2001; Smith, 2006). 
With greater degrees of intellectual defi cit— moderate retardation (IQs of 40 to 54), 
severe retardation (IQs of 25 to 39), and profound retardation (IQs below 25)—the dif-
fi culties are more pronounced. For people with moderate retardation, defi cits are 
obvious early, with language and motor skills lagging behind those of peers. Although 
these individuals can hold simple jobs, they need to have a moderate degree of 
supervision throughout their lives. Individuals with severe and profound mental 
retardation are generally unable to function independently and typically require care 
for their entire lives (Garwick, 2007).