Types of intellectual disability (and characteristics)

March 29, 2024

Oligophrenia, mental retardation, intellectual disability ... all these words refer to the same concept, with which we refer to those people who have cognitive resources lower than expected due to their chronological age. People presenting any of the types of intellectual disability .

This type of disability causes, as a general rule, severe difficulties of adaptation to the environment, unless they are granted a sufficient level of help. But intellectual disability is not unique and homogeneous in all people who suffer from it, but we can find different types or degrees depending on the degree of functional impairment and level of Intellectual Quotient .

The normal distribution and intelligence

Intelligence is a construct that refers to the ability of the individual to be able to adapt to the environment and solve the situations you are with. Regardless of how it is seen within the multiple theories in this regard, different people will have differently organized and will be affected their mental abilities for various reasons and variables. Each one of us has a specific and specific skill or ability level in different areas and abilities, including the ability to solve problems and adapt to the environment.

To assess the level of intelligence of the population the level of Intellectual Quotient has been used in a traditional way , understood as the relationship between mental age and chronological age of the individual to be assessed. Taking into account that there is a great variability in the scores reflected by the population as a whole, it is necessary to bear in mind that it is always going to be expected that there will be a certain dispersion of scores around the average. This expected dispersion is conceptualized as standard deviation.

Statistically, intelligence follows a normal distribution. That is to say, if we punctuate the cognitive abilities of a population with an intelligence test, a vast majority of people would have very similar scores to each other whereas few individuals would have scores that are far from the majority. People with this type of score, away from the majority, could either score more or less.

Having set the average of Intellectual Quotient in a value of 100 and being the standard deviation of 15, values that are at a distance of at least two standard deviations are considered normative. If these two deviations are given above, we would be talking about giftedness, while if values are given two deviations below the average we will be talking about a level of intelligence corresponding to intellectual disability.

Related article: "Intelligence: Factor G and Spearman's Bifactorial Theory"

Types of intellectual disability

Intellectual disability is understood as a condition in which people who suffer from it have severe limitations and deficiencies in intellectual functioning, having problems in reasoning, planning, problem solving or learning.

In addition, these people have deficiencies in adapting to the environment, needing help in one or more dimensions of human functioning so that your daily life is not limited in your personal autonomy and social participation . It is classified as a neurodevelopmental disorder, and it is necessary that these difficulties be observed during development.

However, this is not a completely homogeneous category, and that is why different types of intellectual disability have been established according to the degree to which they are far from the average.

Different degrees of disability

Cognitive skills are important to be able to respond efficiently to the demands of the environment. Thus, people who have a reduced capacity in this type of skills will find it difficult to cope with the situations that appear throughout their lives.

Depending on the level of difficulty that these people find in their day to day and the level of IQ reflected by intelligence test, the existence of several groups, types or degrees of intellectual disability has been considered .

However, we must bear in mind that the degree of IQ is not an absolute measure, but relative; it always depends on a reference group, since the Intellectual Quotient indicates the position occupied by the person in the distribution of scores obtained. Therefore, by changing the reference group a score may be within the normal range of intelligence or what is considered to be intellectual disability. The IC indicates individual differences between people, but to measure in itself the true cognitive abilities of a person in an exact way there are other tools and methods.

1. Mild

It is considered mild or slight intellectual disability to that possessed by people with an Intellectual Quotient that is between 50 and 70 , corresponding to two standard deviations below the population mean. Most people with intellectual disabilities (approximately 85%) are at this level.

People with this degree of intellectual disability have mainly a delay in the cognitive field and a slight involvement in the sensorimotor . Learning capacities are slightly behind, but they can remain in the educational system, be trained and exercise an appropriate professional activity. They are able to read, write and perform calculations, although they usually require a longer learning period than others. In fact, it is possible that during preschool there are no big differences with their peers.

You can see some problems in memory, executive functions and abstract thinking. Their communicative and social skills may be good, although they usually show some difficulty in detecting social cues and regulating their emotions and behavior. These are mostly autonomous people, requiring social orientation in specific situations, and help in legal, economic or raising children. Although they need support, their adaptation to the environment is usually satisfactory.

2. Moderate

In this degree of intellectual disability the difficulties are greater. At an educational level, they can usually benefit from specific job training, generally in the face of performing low-skilled jobs with supervision. They can have autonomy in self-care and displacement .

The conceptual abilities of these subjects develop very slowly, there being a great difference with respect to the peer group. They usually need help when the tasks to carry out require processing complex concepts. His communication is efficient in the social, although not very complex. The subject is able to establish relationships with the environment and make new links with people outside the family.

Although they may have problems following social conventions, they usually adapt well to community life, especially with supervision. The individual can take responsibility for their own decisions and participate in social life, although with help and with a prolonged period of learning.

People with a moderate degree of intellectual disability usually reflect an IC of between 35-50 .

3. Serious

With an Intellectual Quotient between 20 and 35 , the problems for people with this level of disability are generally of great importance, requiring assistance and continued supervision. Many of them have neurological damage .

At a conceptual level, the abilities of people who suffer from this degree of intellectual disability are reduced, with little understanding of reading and numerical concepts. Communicationally language is possible but it is limited, focusing on the present and being frequent that they use holofrases or single words. They include simple gestural and oral communication, being the relationship with loved ones a source of joy.

In day-to-day activities these subjects always need to be supervised and cared for, depending on aids and custodians. They can learn to talk and perform simple tasks. Their adaptation to the community can be good unless they have some other associated disability. Acquiring skills is possible, needing constant help and a long learning process . Some of them self-harm. At a legal level, they are considered incapable of making their own decisions.

4. Deep

The highest degree of intellectual disability and also the most infrequent, people with this level of disability have an IQ of less than 20. They need to be cared for constantly, having very few options unless they enjoy a very high level of help and supervision. In general, their survival rate is low.

They mostly have great difficulties and other serious disabilities, as well as major neurological problems. At the conceptual level these people employ they take into account mainly physical concepts, suffering serious difficulties in using symbolic processes . The use of objects for self-care, work or leisure is possible, but other alterations frequently prevent them from being used functionally. At sensorimotor level they are very limited, as well as at the communicative level.

Regarding the communicational and social field, they can understand instructions and gestures, but they have to be simple and direct. Emotional expression occurs mainly through direct non-verbal communication, without symbolism. They enjoy the relationship with known people. On a practical level, the subject will have dependency for most activities , although they can help in some activities, enabling them to participate in the daily life of the home and society.

The need for aid

As a conclusion to this article it is relevant to mention that a person is only disabled to the extent that it does not have the tools to adapt to the environment , due to their difficulties and the lack of support to solve them. In this sense, intellectual disability is not an exception.We can not limit ourselves to pointing out that someone has an intellectual disability and limiting the problem to the individual; society has a lot to say when it comes to changing the living conditions of these people in vulnerable situations.

Work must be done from the different disciplines (psychology, judicial scope, legislative area, education and social assistance, among others) in order that these people and the people who care for them can participate in an active way in the social life of the community, establishing bridges between the capacities of each individual and what society can offer and demand by granting specific and functional aid.