Human performance and assistive technologies

At the most fundamental level, assistive technology systems represent someone (a person with a disability) doing something (an activity) somewhere (within a context). The major goal of the provision of assistive technology is to enable an individual with disabilities to meet specific needs, consistent with his or her skills and the unique functions within the contexts of that person’s daily life. This assistive technology system selection process emphasizes use of available function (human component) to accomplish what is desired (activity) in a given context (place, environment, and other people). We are not concerned as much with remediation of a disability as we are with enabling functional results and helping the individual to achieve what he or she wants to accomplish. Enabling functional results requires that we maximize the skills of the person with a disability, which places human performance at the center of our system. The primary outputs of the assistive technology system are communication, mobility, manipulation, and cognition. In this chapter we discuss means of achieving these outputs in a general sense. More specific applications that may facilitate performance in these areas will be discussed in subsequent chapters.

This book is directed toward rehabilitation assistants (e.g., OTAs, PTAs, and speech assistants) that interact with persons with disabilities on a frequent, often daily, basis. Consequently, rehabilitation assistants are in an excellent position to report on the daily activities and function of a person with a disability. They can provide information on daily and long-term performance, such as how a person’s function changes over the course of the day, perhaps as fatigue affects functional performance, or the effect of a social context or activity on function—for example, for a person with dementia singing with other residents may encourage more function than watching a movie.

Let’s start with a case study of an individual who uses an assistive device for communication. It provides a brief illustration of a situation of an individual with a disability who uses assistive technology to communicate. It hints at factors that influence whether or not a device will be useful in a given context and how individuals within the environment can affect the use of a device. It raises several issues involving the person using the device, the device itself, and the context in which it is used. It also points to the need for an effective evaluation that will enable selection of the most appropriate device and suggests that the interaction between the person, the device, and the contexts will influence the performance of a desired activity.

A Human Activity Assistive Technology Model

The human activity assistive technology (HAAT) model is proposed as a framework for understanding the place of assistive technology in the lives of persons with disabilities, guiding both clinical applications and research investigations. The model has four components—the human, the activity, the assistive technology, and the context in which these three integrated factors exist. The human component includes physical, cognitive, and emotional elements; activity includes self-care, productivity, and leisure; assistive technology includes intrinsic and extrinsic enablers; and the context includes physical, social, cultural, and institutional contexts. Each of the components shown in Figure 2-1 plays a unique part in the total system. Consideration of each of these elements and their interaction is necessary for the design, selection, implementation, and evaluation of appropriate assistive technology and for research into various aspects of assistive technology development and use. The characterization of the model—with the elements of human, activity, and assistive technology forming a collective that is nested within a physical, social, cultural, and environmental context—is intended to show the dynamic interaction between the initial three factors and the pervasive influence on them, both individually and collectively, of the various contexts. The interaction among the components of the HAAT model can be illustrated through application to our case study of Marion.

Case Study – Marion (Part 2)

One activity in which Marion needs and wants to engage is communication. She communicates in a variety of different settings, including school, home, in social situations with friends, with others with whom she is familiar, and with strangers. Without the use of a communication aid, Marion’s speech is not readily understood by many of her communication partners. She is limited in her ability to engage in conversation, relay her needs, and express her opinions and ideas.

The communication board (the assistive technology) enables her communication by providing a means of conveying her ideas other than by spoken or written language. The communication board is particularly useful in certain contexts in which she communicates with partners with whom she is familiar and who are familiar with her use of the board. In these situations, communication can be a very quick and satisfactory process. However, the communication board is less useful with unfamiliar partners who are not familiar with its use or who may not have the patience to wait as Marion accesses the symbols on the board. Shortcuts that Marion has devised on the board will not be useful with unfamiliar partners. A voice output communication aid provides more effective communication in this latter situation, because the output is clear and audible and Marion can pre-program phrases and text for quick retrieval. However, there are settings in which the VOCA would not be appropriate, such as a very noisy environment or one in which its use would disturb others, such as a movie theatre.

This brief example illustrates how the user’s abilities are enhanced or augmented by the assistive technology in order to complete a desired activity. It also demonstrates that an assistive technology solution that works in one context is not as effective in another. The illustration shows that aspects of the person, the desired activity, the assistive technology, and the environment in which the technology will be used must be considered to ensure a satisfactory means to engage in daily living. What works for one person in a particular setting for a particular activity may not be successful for another person in different circumstances. Indeed, a solution that works in one context may not transfer to another context for the same person.

The activity

The activity is the fundamental element of the HAAT model shown in Figures 2-1 and 2-2 and it defines the overall goal of the assistive technology system. The activity is the process of doing something, and it represents the functional result of human performance. Activities are carried out as part of our daily living, are necessary to human existence, can be learned, and are governed by the society and culture in which we live.¹⁰

The profession of occupational therapy is based on the use of occupation, or activity, in the daily lives of individuals. Both the American Occupational Therapy Association (2002) and the Canadian Association of Occupational Therapists (2002) define these terms in the same way:

Activities are categorized in three basic performance areas: activities of daily living, work and productive activities, and play and leisure.¹⁰ Activities of daily living include dressing, hygiene, grooming, bathing, eating, personal device care, communication, health maintenance, socialization, taking medications, sexual expression, responding to an emergency, and mobility. Included in work/productive activities are home management activities, educational activities, vocational activities, and care of others. The play and leisure area includes activities related to self-expression, enjoyment, or relaxation. While these lists suggest that certain activities form specific categories, in reality the meaning an individual gives to an occupation determines in which performance area it is placed.^10,25 For example, gardening may be a productive activity for one person and a leisure activity for another. Further, the meaning of an activity may vary depending on the role the individual assumes at the time the activity is performed. Christiansen and Baum (1997)¹² define roles as “positions in society having expected responsibilities and privileges” (p. 54).

A person can have multiple roles simultaneously, and roles change throughout the person’s life span. Examples of roles we hold during our lifetime include student, parent, son or daughter, sibling, employee, friend, and homemaker. Performance of an activity may differ depending on the nature of the role in which it is performed. For example, a parent reading to her child reads in a different way than when the reading is completed as part of the role of worker or student. Activities can be broken down into smaller tasks. The skills and abilities intrinsic to the human allow the individual to complete a series of tasks to produce the functional outcome of the activity. These skills may require any combination of physical or cognitive abilities or emotional aids for their successful completion. When an individual lacks the capacity to complete a task, the manner in which that task is completed, including the use of assistive technologies, must be changed. Understanding the activity is part of the assistive technology selection process because it requires identifying the tasks, skills, and abilities required for successful completion; the meaning the individual gives to the activity; and the different roles in which the individual uses the activity. Returning to the case study of Marion, communication is identified as the activity in which she needs to participate. She has the cognitive skills to complete the activity but not the physical ones. Further, the contexts in which she must communicate, including with different communication partners, affects her performance of this activity. Careful analysis of the activity of communication for Marion is required to identify the communication device that is most useful to her.

The human

The model in Figure 2-1 represents someone doing something someplace. Who is doing it? The individual with a disability is “operating” the system. Figure 2-3 highlights the human component of the HAAT model. Two theoretical approaches are useful when considering the human operator and his or her ability to use assistive technology: (1) the conceptualization of the person from the Canadian Model of Occupational Performance (CMOP)¹⁰ and (2) occupational competence.²⁴ The CMOP conceptualizes human abilities as comprised of three elements: physical, cognitive, and affective.¹⁰ Physical abilities include strength, coordination, range of motion, balance, and other physical properties. Cognitive components include attention, judgment, problem solving, concentration, and alertness, while affect includes emotional elements. It is important to understand a person’s abilities in each of these areas as they relate to the use of the desired technology. An appropriate match is needed between the person’s abilities and the requirements of the technology to ensure effective use.³¹ Where a mismatch occurs, devices will be misused or abandoned, as they do not meet the user’s needs.

In the HAAT model, the motor outputs of communication, mobility, and manipulation are required in order to accomplish the goals defined by activities. These three areas require that the human operator possess motor output skills as well as sensory function to perform these activities. These are akin to the physical domain of CMOP. For example, visual or auditory input is typically required for communication. If these skills are impaired, assistive technology systems can provide assistance by requiring different skills. For example, when a hearing aid compensates for reduced hearing thresholds or a Braille output system avoids the need for visual reading, the assistive technology provides replacement or augmentation of a sensory system. Finally, central processing is required for the successful completion of activities. Components of central processing include perception, motor control, and cognition, similar to the CMOP cognitive domain. If the human’s capabilities are limited, then assistive technology systems can often provide assistance in this area as well. For example, procedures for device operation may be simplified for an individual who experiences difficulty in sequencing tasks, or recall aids may be incorporated to assist someone who has memory deficits. Psychological function (referred to as “affect” in CMOP) influences performance of activities, for example, through motivation, self-efficacy, and perception of the value of the activity. These human performance components of the HAAT model are examined in detail in Chapter 3.

Occupational competence gives a dynamic context to the understanding of human abilities and how a person changes and adapts their engagement in activity in response to environmental demands and changes in their own abilities. While CMOP is useful to conceptualize human behavior at a given point in time, occupational competence helps understand behavior across the life span. Five constructs are important to the notion of occupational competence.²⁴ Capacity refers to the potential skill, ability, or knowledge that an individual can apply to a given activity. Capacity changes with development and aging, as well as with trauma or illness. Effectance is the extent to which the individual reaches or uses their capacity in a given task. When a person is motivated to perform well in an activity, effectance approaches capacity. Affordances are those environmental elements that can facilitate performance of a task, providing the individual perceives them as a facilitator. Self-efficacy is a well-known concept described by Bandura (1977)⁵ that refers to an individual’s belief that they can be successful in a particular situation. Finally, competence is the selfperception of satisfactory performance as compared to some defined standard.

Collectively, these constructs contribute to occupational competence, i.e., the ability to meet the demands that are required for successful engagement in various life roles.²⁴ Thus, expectations by and of the individual, relative to performance of an activity, change as the person grows and acquires new skills, or conversely, as they age or experience illness or trauma and lose skills. This notion of occupational competence illustrates the dynamic elements of physical and cognitive capacities and how they are influenced by the individual’s attitudinal and motivational characteristics to meet the demands of various life roles.

The contexts

Over the past several decades the models used to describe disability and the disablement process have changed dramatically.²⁹ In the 1950s the focus was on the disabled person’s “problem” of an inability to participate in work, play, education, and daily activities of living; this problem was “in the person”; that is, it was strictly the result of the impairment. More recently, there has been an increasing awareness that the difficulties experienced by individuals with disabilities result as much from environmental factors as from the impairment itself. Initially the focus was on the physical or built environment, with much effort to make curb cuts, install elevators, and so on. As individuals with disabilities began to participate more fully in society, it became evident that the social and attitudinal barriers were just as great as the physical ones. A “minority group model” of disability emerged in which the attention was shifted away from the impairment to the social, political, and environmental disadvantages forced on people who have disabilities.⁹ Bickenbach et al. (1999) conceptualized disability in a different way.⁶ In their view, disability was a universal experience if a person lives long enough. Contrary to the minority group model, which advocated for special status for individuals with disabilities, the universalism concept advocated for broader social justice and policies that were more inclusive of persons with disabilities, actions that would benefit a broader segment of society. With these new perspectives, problems of societal participation were no longer attributed to the impairment of the person with a disability. Rather, lack of participation in society was viewed as resulting from limitations in the social and physical environments. The emphasis on participation in ICF is indicative of the move away from a “problem in the person” concept to a “problem in the environment” model. In the HAAT model we have captured these external influences in the context.

As shown in Figure 2-4, the context includes four major considerations. These are (1) the physical context, including natural and built surroundings and physical parameters, (2) the social context (with peers and with strangers), (3) the cultural context, and (4) the institutional context including formal legal, legislative, and socio-cultural institutions such as religious institutions. The contexts in which the human carries out the activity can be determining factors in whether the person successfully uses an assistive technology system. The supports and barriers in these environments are important considerations in the selection and evaluation of these systems.

One further distinction is important in the consideration of context, which is the level of the environment. Three levels of environments have been described in the literature: microenvironment, meso environment, and macro environment.^17,22 The microenvironment refers to the closest, most intimate environments in which a person functions, such as their home, school, or work setting. Here the person and their abilities are known, roles are defined and rules and expectations are understood. The meso environment describes those settings in which a person functions less frequently and includes various community facilities such as community centers, shopping malls, and churches. The macro environment refers to the broader social and cultural contexts that impose a legislative and moral behavioral framework on the person.²² Each of these environments influences the use of assistive technology systems. It is important to understand how each aids or hinders the use of assistive technology.

Physical Context

Perhaps the easiest environmental component to understand is the physical context. This context involves the physical attributes of the environment that enable, hinder, or affect performance of daily activities, either with or without assistive technology. It is important to identify the physical attributes of the environments in which the individual intends to use an assistive device to determine whether or not the device is compatible with those environments. In some cases, a device will work in one environment but not in another. Voice recognition software is an example of a device that does not readily transfer from one environment to another. In the relative quiet of an individual’s home, voice recognition software may be an excellent alternative to direct input of computer keystrokes. However, it may not work in an office environment where noise interferes with the software and its use may interfere with the work of colleagues in close proximity to the individual.

A distinction that is important to understanding the physical environment is between the natural and built surroundings. The natural surroundings include non–man-made elements such as parks. Conversely, built surroundings include those structures or elements that are man-made, such as buildings and sidewalks. It is critical to know whether the individual intends to use an assistive device in both built and natural surroundings because it will affect the technology selection and performance. A wheelchair with tires that facilitate travel over uneven and loose surfaces should be recommended for a person who intends to use a chair both indoors and outdoors on unpaved areas. One with smooth tires will not be useful for outdoor travel.

Assessment of the physical environment for selection or evaluation of assistive technology begins with the activities the person wants or needs to do and in which environments those activities will be performed. Within buildings, a person needs to enter and exit the building, access various locations, possibly move between levels, and perform a variety of daily activities. Further, a person needs to move from one environment to another (e.g., home to place of employment). Some of the physical aspects of the environment that should be considered include the width of hallways or doorways; distances between locations the person must navigate; surfaces (e.g., carpets, transitions, and floor surfaces); the height and weight of devices and objects (e.g., doors) that the person must manipulate; and sensory cues (visual or auditory) required to successfully complete daily activities. Physical safety is an important consideration when assessing the environment.

Three commonly measured parameters of the physical environment—heat (related to temperature), sound, and light—most directly affect the performance of assistive technologies. Many materials are sensitive to temperature and are affected by excessive heat or cold. For example, the properties of foams and gels used in seat cushions can change under conditions of very high or very low temperatures. Liquid crystal displays are affected by temperature as well as by ambient (existing) light.

Ambient light in classrooms or work environments can affect the use of assistive technologies. Some displays emit light and are better in conditions of reduced ambient light, whereas others reflect light and are better used in bright light. For example, lighting that is appropriate for normal classroom work may be too bright for the use of some displays, such as computer screens, because of glare.

Ambient sound (including noise) can have a major effect on the intelligibility of voice synthesizers or voice recognition systems. Sounds generated by devices such as printers, power wheelchairs, voice output communication aids, and auditory feedback from computer programs can be disruptive in a classroom. Church and Glennen (1992)¹³ discuss ways of controlling sound and lighting to avoid interference in the classroom while still facilitating the functional gains provided by the assistive technology.

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