The intellectual and developmental disability ( DIyD ) is the most frequent personal condition of disability in the population and among students.

Concept of Intellectual Disability

The term “intellectual and developmental disability” was adopted in June 2006, after a vote by the members of the American Association on Intellectual and Developmental Disabilities (AIDD). It was previously called American Association on Mental Retardation (AAMR).

There are at least three known names for this group: “mental deficiency”, “mental retardation” and “intellectual and developmental disability”.

The IYDD has modified the name, definition, diagnosis and classification as a consequence of the advances in the different disciplines involved in this subject: medicine, psychology and education.

A term to avoid stigmatization

The previous concept was changed to this new one so that labels or social prejudices were minimized such as: visions centered on deficit, on slow and unadjusted mental functioning, etc.

The new name aims to take advantage of a new conception of development that is nourished by the contributions of socio-cultural and ecological theories.

It allows a functional vision of development , which refers that a person can have different contexts and throughout the life cycle. In turn, it provides the concept of disability that is nourished by the contributions of the International Classification of Functioning, of Disability and of the WHO , and that recognises the social origin of the difficulties experienced by the person suffering from IDD.

On the other hand, he also understands intellectual disability as a developmental disorder that has much in common with other developmental problems that can affect children.

Objectives of this monograph

In this article we will try to provide a current vision of intellectual disability and development based on the supports paradigm and on a conception of this disability as a function of the interaction between the independent functioning of the person and the contexts in which he or she lives, learns, works and enjoys; to provide a general framework and some tools for the assessment of students with IDD; and to offer some answers to promote their development.

What do we mean by intellectual and developmental disabilities?

First of all, let us define intellectual disability and the categories that constitute it.

What is intellectual disability?

There are four approaches in this field:

  • Social approach : historically these people were defined as mentally deficient or retarded because they were unable to adapt socially to their environment. The emphasis on intellectual difficulties did not come until later and for a while it was the inappropriate social behaviour that was of most concern.
  • Clinical approach : with the rise of the clinical model, the definition objective was changed. The focus shifted to the symptoms and clinical manifestations of the various syndromes. More attention was paid to the organic and pathological aspects of ID.
  • Intellectual approach : from the interest in intelligence as a construct and in intelligence tests, the approach to DI undergoes another change. It involves an emphasis on the measure of intelligence of these people expressed in terms of IQ. The most important consequence was the definition and classification of people with ID based on the scores obtained in the intelligence tests.
  • Intellectual and social approach : it was not until 1959 that the importance of these two components in the conception of ID was recognised: the low intellectual functioning and the difficulties in adaptive behaviour, which have been maintained until today.

Theoretical and practical models of intellectual disability

Models with which persons with intellectual disabilities have been conceptualized and which justified certain professional practices. There are three main models :

Charity model

From the end of the 19th century and for almost half of the 20th century, people with disabilities were kept apart from society and entrusted to large charitable asylum institutions. The attention they received was of a welfare type and obeyed the charitable conception of public action. They did not think of it as something social or rehabilitative.

Rehabilitation-therapeutic model

It has spread in Spain since the end of the IIGM in the 1970s. It implies the adoption of the clinical model in the diagnosis and treatment of people with ID , and the predominance of specialization. The model coincides with the rise of the aforementioned clinical approach. The diagnosis of ID focuses on the individual’s deficit and they are classified into categories according to their IQ. The problem is considered to be within the subject and specialized institutions are created according to the nature of the problem to care for them.

Educational model

It started in our country in the 1980s. It is characterized by the adoption of the principle of normalization in all the stages of the life of these people. They began to be considered as having the same rights as their peers to education, health, work and a dignified life. Education should be provided, if possible, in ordinary centres, the diagnosis should prioritise the capacities of these people and focus on the support they will need to respond to the demands of the different living environments.

History of the definition of the concept

The AAIDD has changed the definition of DI up to 10 times. The last one was in 2002. It is a definition that goes beyond that of 1992 but maintains some of its key exceptions: the fact that mental retardation is not taken as an absolute trait of the person, but as the expression of the interaction between the person , with some intellectual and adaptive limitations, and the environment; and the emphasis on supports.

In the 1992 definition, the categories disappear. They are explicitly rejected and it is stated that people with mental retardation should not be classified on the basis of the traditional categories, but that thought should be given to the support they may need to increase their social participation.

Despite this, the 1992 definition meant a major improvement for people with ID, but was not without its critics :

  • The imprecision for diagnostic purposes : did not allow to establish clearly who was or was not a person with mental retardation, who was eligible for certain services.
  • The lack of operational definitions for research.
  • The fact that the evolutionary aspects of these people are not sufficiently considered.
  • The imprecision and impossibility of measuring the intensity of the support these people require.

For this reason, the AAIDD proposes a new definition built on that of 1992. It creates a system of diagnosing, classifying and planning support for people with mental retardation.

The current definition

The new definition of mental retardation proposed by AAMR is as follows:

“Mental retardation is a disability characterized by significant limitations in both intellectual functioning and adaptive behavior expressed in conceptual, social, and practical skills. This disability originates before the age of 18.”

  • “Mental retardation is a disability”: a disability is the expression of limitations in the functioning of the individual within a social context that result in significant disadvantages.
  • “…which is characterized by significant limitations in both intellectual functioning”: intelligence is a general mental capacity that includes the act of reasoning, planning, problem solving, abstract thinking, etc. It is best represented by IQ, which is two standard deviations below the average.
  • “…as in adaptive behavior expressed in conceptual, social and practical skills”: adaptive behavior is the set of conceptual, social and practical skills that people learn to function in daily life.
  • “This ability originates before the age of 18”: 18 corresponds to the age at which individuals assume adult roles in our society.

With this definition , the cognitive basis of the problem is again stressed , but from a model that emphasises social and practical competence, which translates into the recognition of the existence of different types of intelligence; a model that reflects the fact that the essence of mental retardation is close to the difficulties of facing daily life, and the fact that limitations in social and practical intelligence explain many of the problems that people with ID have in community and at work.

It extends the concept to other population groups, in particular the forgotten generation: an expression that includes people with limited intelligence.

The aspects that change with this last definition are:

  • It includes a criterion of two standard deviations for the measurement of intelligence and adaptive behavior.
  • It includes a new dimension: participation, interaction and social role.
  • A new way of conceptualizing and measuring supports.
  • It develops and extends the three-step evaluation process.
  • A stronger link is favoured between the 2002 system and other diagnostic and classification systems such as the DSM-IV, the ICD-10 and the ICF.

As in the 1992 definition, the definition incorporates the following five assumptions :

  1. Limitations on current functioning have to be considered within the context of the typical community environments of their peers of the same age and culture.
  2. An adequate assessment has to consider cultural and linguistic diversity, and also differences in communication, sensory, motor and behavioural factors.
  3. Within the same individual, limitations often coexist with strengths.
  4. An important objective in describing the limitations is to develop a profile of the supports needed.
  5. With appropriate personalized supports over a sustained period of time, the way people with mental retardation live will generally improve.

Mental retardation is understood as part of a multidimensional model that provides a way to describe a person through five dimensions that include all aspects of the individual and the world in which he or she lives.

The model includes three key elements: the person , the environment in which they live , and the supports .

These elements are represented in the framework of the five dimensions that are projected in the daily functioning of the person through the supports. The supports have a mediating role in the life of persons with intellectual disabilities.

This leads to a broader concept of ID , which involves understanding that the explanation of people’s daily behaviour does not end with the effect of the five dimensions , but with the support they may receive in their living environment.

Trends that have prevailed in the field of DI

  • An approach to DI from an ecological perspective that focuses on the interaction between the person and their environment.
  • Disability is characterized by limitations in functioning, rather than a permanent feature of the person.
  • The multidimensionality of DI is recognized.
  • The need to link evaluation and intervention more firmly.
  • The recognition that an accurate diagnosis of ID often requires, along with available assessment information, sound clinical judgment.

Characteristics and causes of intellectual and developmental disabilities

Three important characteristics are found: limitations in intellectual functioning, limitations in adaptive behavior, and need for supports.

1. Limitations in intellectual functioning : intelligence refers to the student’s ability to solve problems, pay attention to relevant information, abstract thinking, remember important information, generalize knowledge from one scenario to another, etc.

It is usually measured by standardized tests. A student has DI when his or her score is two standard deviations below the mean.

The specific difficulties presented by people with ID

They usually present difficulties in these three areas :

a) Memory : people with DI often show limitations in their memory, especially the one known as MCP, which has to do with their ability to remember information that must be stored for seconds or hours, as it usually happens in class. This is more evident in the cognitive aspects than in the emotional ones. Strategies can be employed to improve capacity.

b) Generalization : refers to the ability to transfer knowledge or behaviour learned in one situation to another. (from school to home, for example).

c) Motivation : research reveals that lack of motivation is associated with previous experiences of failure. The difficulties in successfully overcoming certain challenges of daily life at home and in the centre make them more vulnerable. If the sign of their experiences can be changed, motivation will also improve.

d) Limitations in adaptive behavior : people with ID usually have limitations in adaptive behavior. Adaptive behaviour refers to the ability to respond to the changing demands of the environment; people learn to adjust/self-regulate behaviour to different life situations and contexts according to age, expectations, etc.

To identify a student’s skills in this field, conceptual, social and practical abilities are usually explored through scales constructed for this purpose. From the results, educational activities can be designed and integrated into the curriculum.

Self-determination is the most central expression of the capabilities inherent in adaptive behavior and is especially relevant for people with ID. Its development is associated with a perception of greater or lesser quality of life.

Causes of Intellectual Disability

There are four categories of causes:

  1. Biomedical : factors related to biological processes, such as genetic disorders or malnutrition
  2. Social : factors related to the quality of the social and family interaction, such as the stimulation or the sensitivity of the parents to the needs of the son or daughter.
  3. Behavioral : factors that refer to behavior that can potentially cause a disorder, such as accidents or the use of certain substances.
  4. Educational : factors that have to do with access to educational services that provide supports to promote cognitive development and adaptive skills.

It should be noted that these factors can be combined in different ways and proportions.

Intellectual disability and quality of life

One of the four characteristics of the emerging disability paradigm is personal well-being, which is closely associated with the concept of quality of life.

The recognition of the rights that people with ID have is implicit in the recognition of the right to a quality life.

Over time, the concept of quality of life has been applied to people with ID. This implies access to services, efficiency and quality of these services that allow them to enjoy the same opportunities as others.

Access to a quality life involves recognising the right to be different and the need for the services offered to be permeable to their particular conditions.

People with ID have certain characteristics that generate specific needs throughout their development, these needs draw the type of support they require to access services that make optimal living conditions possible.

Quality of life is defined as a concept that reflects the living conditions desired by a person in relation to his or her life at home and in the community; at work; and in relation to health and well-being.

Quality of life is a subjective phenomenon based on a person’s perception of a set of aspects relating to their life experience.

The concept of quality of life

According to Schalock and Verdugo, the concept of quality of life (CV) is being used in three different ways:

  • As a sensitizing concept that serves as a reference and guide from the perspective of the individual, indicating what is important to him.
  • As a unifying concept that provides a framework for conceptualizing, measuring and applying the VC construct
  • As a social construct that becomes a predominant principle to promote the well-being of the person.

Promoting well-being in people with intellectual disabilities

In working to promote the well-being and quality of life of people with ID, the importance of eight central dimensions and certain indicators is recognized:

  • Emotional well-being : happiness, self-concept, etc.
  • Interpersonal relations : intimacy, family, friends, etc.
  • Material welfare : belongings, security, work, etc.
  • Personal development : education, skills, competences, etc.
  • Physical well-being : health, nutrition, etc.
  • Self-determination : elections, personal control, etc.
  • Social inclusion l : acceptance, participation in the community, etc.
  • Rights : privacy, freedoms, etc.

Services and resources for persons with intellectual disabilities

The services and resources offered to people with ID throughout the life cycle need to be targeted to meet their needs in order to meet the demands of the various contexts in which they live and to enable them to live a quality life.

Characteristics that define an optimal environment :

  • Presence in the community : sharing ordinary places that define the life of the community.
  • Elections : the experience of autonomy, decision making, self-regulation
  • Competence : the opportunity to learn and perform functional and meaningful activities.
  • Respect : the reality of being valued in the community.
  • Participation in the community : the experience of being part of a growing network of family and friends

About people with ID in the educational context: “Students with intellectual disabilities: assessment, monitoring and inclusion”

Bibliographic references:

  • Gilman, C.J., Morreau, L.E. ALSC; Adaptive Skills Curriculum. Personal Life Skills. Messenger Editions.
  • Gilman, C.J., Morreau, L.E. ALSC; Adaptive Skills Curriculum. Home Life Skills. Messenger Editions.
  • Gilman, C.J., Morreau, L.E. ALSC; Adaptive Skills Curriculum. Community Living Skills. Messenger Editions.
  • Gilman, C.J., Morreau, L.E. ALSC; Adaptive Skills Curriculum. Work skills. Messenger editions.
  • FEAPS. Positive behavioral support. Some tools for coping with difficult behaviours.
  • FEAPS. Person-centered planning. Experience of the San Francisco de Borja Foundation for people with intellectual disabilities.