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This is a psychology lesson on levels and characteristics of mental retardation


Science, Social Studies  


9, 10, 11, 12  

Title – Levels of Mental Retardation
By – Edmund Sass
Primary Subject – Science
Secondary Subjects – Social Studies
Grade Level – 9-12 and above

Overview: This activity introduces the topics of levels and characteristics of mental retardation. It is meant as a follow-up to Mental Retardation: Definitions and Terminology

Goal: Students will learn about levels of mental retardation and characteristics of individuals with mental retardation.


      1. Students will develop lists of characteristics of individuals with different levels of mental retardation.

    2. Students will know and understand two different classification systems regarding levels of mental retardation.

Materials Needed: (attached below)

  • Traditional Levels of Mental Retardation Based on IQ (overhead transparency);
  • AAMR Levels of Support (overhead transparency);
  • Mental Retardation: Three Case Descriptions (handout);
  • Mental Retardation: Characteristics (handout)

Introduction/Anticipatory Set:

    Begin the lesson by asking students if any of them know someone with mental retardation. Call on two or three students and ask them to describe the person they know who has mental retardation. (What is the person like?) Then ask if they know the person’s level of mental retardation. Explain that during today’s class they will be learning about two systems for determining levels of mental retardation, and that by the end of class, they should be able to identify into which level of mental retardation the person they know would best fit.


      Using the overhead transparency,

Traditional Levels of Mental Retardation Based on IQ

      , familiarize students with traditional, IQ-based levels of mental retardation:

      • mild (IQ range 55 -70),
      • moderate (IQ range 40 – 54),
      • severe (IQ range 25 – 39), and
      • profound (below 25)

      as well as the traditional (though no longer appropriate) special education terminology (educable and trainable mental retardation). Explain that the two middle levels, moderate and severe, are often considered together. Then explain that the American Association on Mental Retardation (AAMR) has now developed a new classification system based on need for support.
      Using a second overhead transparency,

AAMR Levels of Support


      briefly describe these four levels:

      • Intermittent,
      • Limited,
      • Extensive, and
      • Pervasive.

      After answering any student questions regarding the two classification systems, divide the students into groups of about four, and distribute the handout, Mental Retardation: Three Case Descriptions (which provides descriptions of individuals at the traditional IQ-based levels of mild, moderate to severe, and profound mental retardation). Inform the students that, assuming the case descriptions are typical, they must:
      1. develop lists of characteristics of individuals with mild, moderate to severe, and profound mental retardation (one list for each of the three levels) including information on physical appearance, rate of development, causation, academic achievement, and adult functioning;
      2) determine the level of support needed by each of the three individuals in the cases.
      Allow 20 to 30 minutes for students to complete these tasks.
      Ask each group to choose a spokesperson.
      When all groups are finished, ask the spokespersons to read their lists. Correct any inaccuracies, and based on the students’ lists, put composite lists of characteristics for each of the three levels on the board. Also, ask the group spokespersons what level of support they believe the individuals in each of the three cases would require. Then distribute the handout titled,

Mental Retardation: Typical Characteristics

    , and ask students to compare their lists of characteristics (and the composite lists on the board) to those on the handout. Comment on any differences.


      Ask the students who, at the beginning of class, described someone they know with mental retardation to speculate as to both the IQ level and need for support of the person they described. Ask if the characteristics on the handout are similar to those of the person they know.
    Conclude the lesson by explaining that although these brief case studies are rather typical, individuals with mental retardation are just that: individuals. Therefore, even within the IQ levels and levels of support, there is a great deal of variation, and the characteristics listed on the board and in the handouts, though typical, are generalizations that do not hold for all individuals with mental retardation.

Assessment: Assess this lesson informally by observing student groups as they complete the activity, or collect the lists of characteristics developed by each group and assess them for accuracy and completeness.

Additional Online Resources:

      Mental Retardation: Update 2002.– ERIC EC Digest #E637. Available at

Traditional Levels of Mental Retardation Based on IQ

Mild Mental Retardation – IQ score in the range of 50-55 to 70

Moderate Mental Retardation – IQ score in the range of 35-40 to 50-55

Severe Mental Retardation – IQ score in the range of 20-25 to 35-40

Profound Mental Retardation – IQ score below 20-25

Reference: Hourcade, J. (2002). “Mental Retardation: Update 2002.” ERIC EC Digest #E637 . Available at

AAMR Levels of Support

Intermittent – Support is not always needed. It is provided on an “as needed” basis and is most likely to be required at life transitions (e.g. moving from school to work).

Limited – Consistent support is required, though not on a daily basis. The
support needed is of a non-intensive nature.

Extensive – Regular, daily support is required in at least some environments
(e.g. daily home-living support).

Pervasive – Daily extensive support, perhaps of a life-sustaining nature, is
required in multiple environments.

Source: American Association on Mental Retardation. (1992). Mental retardation: Definition, classification, and systems of supports. Washington, D. C.: American Association on Mental Retardation.

Mental Retardation: Three Case Descriptions


Mild Mental Retardation

John is a 26-year-old man who received special education for most of his schooling. He is currently employed as a night janitor at a brewery. John has worked there for about eight years, having begun on a part-time basis while he was still in high school. He is married and has one child.

John began receiving special education while he was in the second grade. During that school year, he was referred for psychological evaluation because he was experiencing severe difficulties in all academic areas. John was administered the Wechsler Intelligence Scale for Children (WISC-R) on which he attained a full-scale IQ score of 68. The report of that evaluation described him as socially immature, but otherwise well adjusted emotionally. He was subsequently placed in the program for students with educable mental retardation (EMR). Throughout the remainder of elementary school, John spent about half the school day in the special education classroom and the remainder of the day in the regular classroom. While in high school, John enrolled in some regular classes, but continued to receive tutoring and some course work through the special education program. During his last two years, he was in a work-study program, and spent half of the day at his job.

His intellectual and academic skills have been reevaluated several times with his IQ scores being slightly higher on each subsequent assessment. When he was last evaluated at age 17, John attained a full-scale IQ score of 73 on the Wechsler Adult Intelligence Scale (WAIS-R). At that time, John’s reading and spelling scores were at the 4th-grade level, and his math skills were similar to those of a 5th-grader. The report of that assessment described him as an average appearing and likeable young man.

John is the youngest of four children. Neither of his parents finished high school, and his father worked as an unskilled laborer before he retired. Two of John’s siblings were also enrolled in special education programs.

Moderate to Severe Mental Retardation

Mary is a 19-year-old woman with moderate mental retardation. She is currently enrolled in the “Adaptive Living Program” at the local high school. She has Down Syndrome, and was identified as having this condition shortly after birth. Mary lives at home with her parents. She is now the “only child” as her older sister is currently away at college, and her older brother is in the Air Force. Mary’s parents, both of whom are college graduates, plan to keep her at home until she completes her schooling (at age 21). They assume she will then move to a semi-independent living situation (SIL). If that does not work out, they will attempt to place her in a local group home.

Mary began attending special education classes at age three, though she and her family began receiving support services shortly after her birth. During kindergarten through sixth grade, she was integrated into a regular classroom for part of each school day. However, the major emphasis of her education has always been the development of self-help skills and functional academics. Mary is able to dress and groom herself and can perform various household chores. She can count, make change, and is able to do basic addition and subtraction. She reads and spells at about a second to third-grade level. Mary is currently receiving job training skills as part of the transition services provided by her school district.

Mary’s learning skills have been evaluated a number of times over the years, with her IQ scores ranging from the mid 30s to the mid 40s. Her most recent evaluation resulted in a mental age of eight years and seven months, and an I.Q. score of 44. The AAMR Adaptive Behavior Scale was also administered, and resulted in an age-equivalent of nine years, two months.


Profound Mental Retardation

Ronald is a 41-year-old man who currently lives in a group home with five other persons with mental retardation. He has lived in various institutional and group-home settings for most of his life. Though Ron is too severely disabled to work in a sheltered workshop, his caretakers do frequently take him out to various community activities and events. He seems to greatly enjoy “getting out,”and his caretakers report that he seems much more alert after these”excursions.”

The cause of Ron’s mental retardation was anoxia (lack of oxygen) at birth which resulted in “severe, profuse brain damage.” He also has cerebral palsy which severely limits the use of his arms and legs. Ronald’s hearing is impaired as well.

The most recent evaluation of Ron’s mental abilities which was conducted in the mid-1980s suggested an overall functioning level of about three years, eight months. However, it is difficult to determine what he actually knows because he has no speech, and the cerebral palsy makes it impossible for him to use sign language. His only form of communication is through the use of a sound-symbol board.

Ron had very little formal education as a child because state law did not mandate that special education be provided for those with severe or profound mental retardation until the late 1970s.

Mental Retardation: Typical Characteristics
(Please note that these are generalizations. There is a great deal of individual variation)

Individuals with mild mental retardation (formerly referred to as “educable”):

  • are likely to need only intermittent to limited support;
  • typically do not “look” different from their non-disabled peers;
  • often have only mild or moderate developmental delays, except in academics, which is often the major area of deficit;
  • therefore, they are often not identified until they enter the school setting, where their cognitive disability is most apparent;
  • in Minnesota, students with mild MR spend most of the school day in the regular classroom;
  • they typically attain 3rd- to 6th-grade academic achievement levels by the time they finish high school;
  • as adults, many, though not all, with mild MR will be able to obtain independent employment;
  • many will marry, have children, and blend rather indistinguishably into the community; for those who achieve total independence, the label of mental retardation is no longer appropriate.

¬†Individuals with moderate to severe mental retardation (formerly called “trainable”):

  • will probably need limited to extensive supports;
  • they are more likely to have a recognizable syndrome (such as Down Syndrome);
  • therefore, may “look” different than their non-disabled peers;
  • their development is often significantly delayed;
  • they are typically identified as infants or toddlers;
  • most begin receiving special education during the preschool years;
  • they may be included in the regular classroom part of the school day (particularly here in Minnesota);
  • but often spend much of the school day in a separate classroom where they learn adaptive living skills;
  • as adults, most individuals with moderate to severe MR will not achieve total independence;
  • rather, they are likely to continue to need limited to extensive support such as that provided in group homes or semi-independent living situations (SILs); some may continue to live with their parents;
  • some individuals with moderate to severe MR may be able to succeed in modified competitive employment situations;
  • however, many will work in supported, non-competitive settings such as sheltered workshops.

Individuals with profound mental retardation:

  • will generally need services at the pervasive level, typically throughout their life;
  • they are likely to have multiple disabilities, particularly in the areas of mobility and communication;
  • therefore, many use wheelchairs and alternate forms of communication;
  • their communication deficits make it difficult to accurately assess their intellectual functioning;
  • in educational settings, they may be placed along with students with moderate to severe MR or in their own classroom;
  • some adults with this level of retardation remain in institutional settings, but most currently live in group homes.

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