Modelling Cognitive Impairment to Improve Universal Access (Universal Access in Human-Computer Interaction)


The purpose of this study is to develop a model of cognitive impairment to help designers consider the range of issues which affect the lives of people living with such impairment. A series of interviews with experts of cognitive impairment was conducted to describe and assess the links between specific medical conditions, including learning disability, specific learning difficulties, autistic spectrum disorders, traumatic brain injury and schizophrenia, and the types of cognitive impairment associated with them. The results reveal some of the most prevalent and serious types of impairment, which – when transformed into design guidance – will help designers make mainstream products more inclusive also for people with cognitive impairment.

Keywords: Cognitive impairment, medical classification, functional capability, design guidance.


Cognitive functions, the mental capacity which allows a person to process information, are the foundation for all human activities [1]. Consequently, any impairment involving these functions, including perception, attention, memory, language and thinking, has a profoundly detrimental effect on the overall functional capability of an individual [2]. Cognitive impairment is associated with many medical conditions; however, the same condition can cause diverse patterns of impairment in different individuals. Some medical conditions are static, others progressive, which adds to the difficulty of assessing their impact. In addition, the co-morbidity of certain medical conditions causes unexpected patterns of cognitive impairment. [3] With certain conditions, such as brain injury, the impact of the impairment depends entirely on the location and extent of brain damage [4]. Furthermore, the number of people living with cognitive disability is growing due to population ageing and the improved survival rates for trauma patients [4; 5]. Neuropsychiatry illnesses and traumatic brain injury are among the leading causes of disability [5]. All this leads to cognitive impairment being an intrinsically complex phenomenon, for which no simple solutions exist.

Considering the impact it has on an individual’s capability to interact with his or her environment, cognitive impairment has not been adequately addressed in current research. Related research conducted in the field of assistive technology has given valuable insight into the design of devices for specific medical conditions and impairment types [e.g. 6; 7; 8]. There are also design guidelines which outline some general aspects of product usability, partly aimed at minimising the cognitive load to users [e.g. 9; 10; 11].

However, there is no systematic and comprehensive review of design issues relating to cognitive impairment. Assistive technology products tend to be developed for a very specific purpose and tailored to each individual, whereas design guidelines are often too general and fail to provide justification or deeper understanding of the needs of the people with cognitive impairment. In addition, it is not easy to estimate the number of people excluded from using a product, as there are no comprehensive statistical data available about the prevalence and incidence of cognitive impairment. In view of the complexity of issues involved and the growing number of people affected, more detailed information about cognitive impairment should be incorporated into the design process. Quantitative information about the prevalence and patterns of cognitive impairment as well as qualitative information about the practical implications of living with cognitive impairment are needed.

Inclusive design has become one of the key approaches of reducing the impact of disability following from impaired functional capability: it aims at minimising the number of people excluded from using a product by making products more accessible and easier to use [12]. Understanding users and knowing their needs and requirements is vitally important to the success of inclusive design [13]. As important as user involvement is in the design process, there are particular challenges when involving users with cognitive impairment. Designers need support if they are to make design inclusive of people with cognitive impairment. One way of supporting designers is to provide them with information that is accurate, relevant, offers them insight and inspiration and is presented in a way that makes it easy to apply. This paper reports the first steps of a study that seeks to develop a model of cognitive impairment providing such design guidance.

This paper is organised as follows: Firstly, a general framework for studying cognitive impairment is presented, followed by a brief description of the research method. Then the results of the study are presented. The paper concludes with a discussion of the work so far and the next steps of the research.

Framework for Studying Cognitive Impairment

This study aims to discover the particular needs and requirements of a person who has cognitive impairment limiting his or her ability to use a product. To this end, it is important to recognise the wide variety of cognitive impairment affecting the functional capability of an individual. Cognitive impairment can be diagnosed through the medical condition causing it. Therefore, building the link between medical conditions and cognitive functions they impair is essential.

In order to get a comprehensive view of the medical conditions with potential impact on cognitive capability, existing and established medical and disability classifications were used. Two widely used classifications, the International Classification of Diseases (ICD-10) [14] and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) [15], were used as the basis for developing the categorisation of medical conditions appropriate for this study. To systematically cover the wide variety of cognitive functions, the International Classification of Functioning, Disability and Health (ICF) [16] was used.

This framework consisting of categories of medical conditions and cognitive functions (see Table 1) was intended to work as a communication tool, translating the medical terminology and the neuropsychological approach to a format that is easier to understand outside medical context.

Table 1. Framework for studying cognitive impairment by linking medical conditions with the cognitive functions they typically impair

Medical condition

Disorders of development

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Learning disability

Autistic spectrum disorders

Specific learning difficulties

Cerebral palsy

Degenerative diseases and ageing


Alzheimer’s disease

Parkinson’s disease

Multiple sclerosis

Acquired conditions

Traumatic brain injury


Mental illnesses



The cognitive functions included in the framework are defined according to the International Classification of Functioning, Disability and Health (ICF) [16] (Table 2). ICF is a classification of human functioning and disability, and it covers body functions and structures and their impairments as well as the potential activity limitations and participation restrictions following from them [16].

Five of the medical conditions in the framework (Table 1) were covered in this first stage of the study.

Table 2. Definitions of cognitive functions included in the framework

Cognitive function


Perception, including visual auditory, visuospatial and tactile perception

Specific mental functions of recognizing and interpreting sensory stimuli

Attention, including sustaining, shifting and dividing attention

Specific mental functions of focusing on an external stimulus or internal experience for the required period of time

Memory, including short-term and long-term memory

Specific mental functions of registering and storing information and retrieving it as needed

Thinking, including abstraction, organisation and planning, time management and problem-solving

Specific mental functions required for complex goal-directed behaviours such as decision-making, abstract thinking, planning and deciding which behaviours are appropriate under what circumstances

Language, including reading, writing and calculation

Specific mental functions of recognizing and using signs, symbols and other components of a language

Learning, including learning to read, write and calculate and acquiring skills

Developing the competence to read written material, to produce symbols that represent words, to perform mathematical operations and learning purposeful actions

Psychomotor functions, including sequencing complex movements

Specific mental functions of control over both motor and psychological events at the body level

Learning disability (also called intellectual disability or mental retardation) affects 1 – 2.5 % of the population in the Western world. Certain medical conditions, such as Down’s syndrome are common causes of learning disability. [17] Learning disability is not a medical condition as such but can be diagnosed based on three factors: 1) intelligence quotient (IQ) below 70; 2) impairment in adaptive behaviour and 3) onset during childhood [18].

Specific learning difficulties (SpLD) differ from learning disability in that they are not indicative of IQ. These learning difficulties include problems of reading (dyslexia), writing (dysgraphia), mathematics (dyscalculia) and motor skills (dyspraxia), which are not a result of poor education. [19; 20] There are no consistent estimates of the prevalence of SpLD but dyslexia in particular is considered fairly widespread, affecting 5 – 17.5 % of the population [21].

Autistic spectrum disorders, including autism and Asperger’s syndrome, are developmental conditions characterised by deficits in social interaction and communication and repetitive patterns of behaviour [22]. Prevalence estimates vary depending on the definition but when considering the whole spectrum, approximately 60 per 10 000 children are affected [23].

Traumatic brain injury (TBI) is the leading cause of death and disability in younger age groups, particularly due to motor vehicle accidents, combat wounds and sports injuries; in older age groups, TBI is most often caused by falls [24; 25]. Although TBI can cause deficits in almost any brain function, impairment in cognitive control functions appear to be common [25]. In the UK, 135 000 people live with long-term problems caused by brain injury [26].

Schizophrenia is an illness of mental health which affects about 1 % of the population [27]. It is among the leading causes of long-term disability worldwide [28]. It is characterised by psychotic symptoms, such as delusions and hallucinations, negative symptoms such as apathy, and impairment in attention, memory, learning and other cognitive functions [27].


A series of expert interviews was conducted in order to learn more about the medical conditions and the types of cognitive impairment associated with them. Using the framework described above, each of the interviews focused on one medical condition and the interviewee was a medical professional working with people who have been diagnosed with the condition. Each interview lasted between 45 minutes and 2 hours and was recorded and transcribed. Each interview consisted of three parts:

1. A semi-structured part where the interviewee was asked about the general aspects of the medical condition they specialised in, the nature of their work in the area and their definition and characterisation of the medical condition in question.

2. A semi-structured part where the interviewee was asked to describe a typical case. They were prompted to think of a person they work with or imagine a person who is in some way characteristic of the medical condition. The interviewee was asked to describe a typical day in the life of the person, their background and any particular problems they might encounter due to their impairment.

3. A structured part where the interviewee was asked to fill in an assessment form in which they evaluated how significant each cognitive function is in causing functional impairment. The assessment was made on a 5-point scale, ranging from ’1 = Not significant’ to ’5 = Very significant’.


The types and severity of cognitive impairment associated with each medical condition vary widely (Fig. 1).

In learning disability, the most significant impairment is to thinking and learning functions. Specific mental functions most often affected are organisation, planning and problem solving. Impairment in these functions can cause difficulties in tasks that require an individual to identify relevant information, integrate separate pieces of information and to use the information to determine an appropriate course of action. Difficulties are exacerbated when there are conflicting pieces of information, as the process of developing a solution is impaired. Handling numerical information and understanding mathematical concepts is particularly difficult.

With specific learning difficulties, dyslexia in particular, mental functions most often impaired are associated with language and learning. Both receptive and expressive skills can be impaired, causing problems of both understanding and creating spoken or written messages. The processes of learning to read, write and calculate are consequently often slow and difficult. Problems occur when an individual is required to copy information or rehearse a sequence of information.

The severity of cognitive impairment in certain medical conditions

Fig. 1. The severity of cognitive impairment in certain medical conditions

Autistic spectrum disorders can cause impairment of any of the cognitive functions. Attention and thinking functions are often among the most significantly impaired areas. Particularly tasks that require cognitive flexibility, abstraction and judgement can cause difficulties. An individual might have problems in understanding the abstract general ideas and qualities that characterise concrete, specific objects. They might find it difficult to solve problems that require changing strategies and evaluating different options. They might also have additional problems with language and their sensitivity to certain perceptual stimuli, particularly auditory and tactile, can be either heightened or diminished.

The types of impairment caused by traumatic brain injury depend on the location and extent of the injury. Generally, the mental functions affected include attention, memory and thinking. An individual might have difficulties in concentration and short-term memory. Thinking impairment might present itself through difficulties of problem solving, decision making and time management. They might find it difficult to discriminate between options to form an opinion and assess the circumstances to make an appropriate judgement.

Schizophrenia is often associated with impairment in thinking functions, particularly organisation and planning. Thinking impairment can also manifest as a problem of insight, resulting in a poor awareness and understanding of oneself and one’s behaviour. Particularly tasks that require sustaining attention for longer periods of time or dividing attention between several stimuli can cause difficulties. Long-term memory might be impaired and the process of retrieving items stored in memory can be problematic. For a significant number of people with schizophrenia, psychomotor problems are significant. This type of impairment generally causes difficulties when an individual is required to control the speed of behaviour or to sequence complex movements.

A summary of the results is presented in Table3. 5


A preliminary analysis of the results reveals that although the patterns of cognitive impairment associated with the medical conditions vary widely, certain types of impairment are more significant than others. Thinking impairment is particularly important, as it is common in many of the medical conditions and causes severe problems in planning, judgement, problem-solving and decision-making. This leads to difficulties in tasks that require an individual to identify relevant information, integrate separate pieces of information and to use the information to determine an appropriate course of action. The individual might find it difficult to solve problems that require evaluating different options and to assess circumstances to make a decision.

Issues such as these can be addressed in the design of products. The goal of this research is to develop a model describing cognitive impairment and its implications for product design. Ultimately, the model would help designers understand users with cognitive impairment. Based on this understanding, they would be able to make informed design decisions, such as identifying potential problems and estimating the number of users excluded because of too demanding design solutions.

The results reported here are based on a preliminary study, and the limited number of interviews might restrict the applicability of the results. Future research will address these issues and a prototype of the model will be tested with designers to ensure its relevance and applicability. When complete, the model of cognitive impairment could provide designers with an understanding of the needs and requirements related to cognitive impairment. The model cannot replace direct contact with actual users but it will help designers understand them, overcome some of the problems related to special populations as design partners, and enhance the eventual interaction with the end-users by providing designers with background information about their needs and requirements. Knowing more about people with cognitive impairment might also help designers to make necessary adaptations to traditional methods and techniques of user research so that they are able to involve cognitively impaired participants in the design process.

Regardless of the complexity of the issues or the limitations of the current study, this is a topic that should be addressed: people with cognitive impairment have needs that designers should be aware of. When provided with the required knowledge and tools, designers will have the ability to help people with cognitive impairment participate as equals in a society which depends on the information processing capability of its members.

Table 3. Summary of the results: typical impairment associated with each medical condition

Medical condition

Characteristic impairment

Learning disability


Organisation and planning, identifying relevant information to determine appropriate actions


Solving problems, analysing conflicting information


Learning to read and write


Understanding numerical information

Specific learning difficulties


Understanding and creating spoken or written messages


Expressing ideas in a coherent manner


Learning to read, write and calculate


Copying or rehearsing information


Additional problems of visual and auditory perception, attention and short-term memory

Autistic spectrum disorders


Understanding abstract concepts


Difficulties in evaluating options and changing strategies to solve problems


Impaired language skills


Heightened or diminished sensitivity to certain stimuli

Traumatic brain injury


Difficulties in focusing and sustaining attention


Impaired short-term memory

Problems of decision-making, problem-solving and time management


Impaired judgement of options and circumstances



Problems of organisation and planning


Poor awareness and understanding of oneself and one’s behaviour


Difficulties in sustaining and dividing attention


Retrieving items from long-term memory


Controlling the speed of behaviour and the sequence of movements

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