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A Functional Approach to the Delivery of Assistive Technology Services

Learn about a model that can be used to guide the planning and delivery of assistive technology services. The focus of the model is on the functions that people need to be able to perform in response to demands that are placed on them from the environment. The model is being used to guide many of NATRI's research activities.

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Context and Rationale

When decisions are being made about the provision of assistive technology services, it is important to base them on factors related to human function rather than on whether the person has been diagnosed as being mentally retarded, physically disabled, or emotionally disturbed. The real issue is the problem the person has in functioning within his or her environment.

For example...

  • A small child with cerebral palsy may lack the fine muscle control that will permit her to fasten buttons so that she can get dressed independently;
<Wednesday, August 16, 2006 material that is being used for instruction in an English class;
  • Another student, due to unknown cause, may be unable to solve math problems; or
  • An adult who has been in an automobile accident may have had a severe head injury that has impaired her ability to speak clearly.

In each of these cases, an environmental demand has been placed on the individuals to perform some function that they will find difficult to execute because of a set of unique circumstances or restriction in their functional capability caused by the lack of personal resources. For example, the individuals just described lack the physical or mental capability to button, read, calculate, or speak.

All of us face situations daily in which environmental demands are placed on us. Our goal is to understand the processes and relate them to the lives of exceptional children who face more complex and restrictive situations. There is the need to know many things, such as the nature of the demands that are being placed on people from the environment and how those demands create the requirements to perform different human functions, such as learning, walking, talking, seeing, and hearing.

It is important to know how such requirements are - or are not - being met by each individual and how factors such as their perceptions and the availability of personal resources such as intelligence, sight, and mobility can affect the responses each person can make. In addition, it is important to understand how availability of external supports, such as special education, different types of therapy, and assistive technology can impact on that person's ability to produce functional responses to the environmental demands.

Although each person with a disability will be unique, the common challenge is to identify and apply the best possible array of special education and related services that will provide support, adjustment, or compensation for the person's functional needs or deficits. A variety of responses may be appropriate. For example, Velcro fasteners may be used to replace buttons on garments for the child having difficulty with buttoning. Braille or audio materials may be provided for the child who cannot read conventional print. The student who has difficulty calculating may require specialized, intense direct math instruction, while a computerized device that produces speech may enable the adult who cannot talk to communicate.

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Areas of Human Function

The term, function, has been used several times in the preceding paragraphs. Function can be defined as an action that a person takes in response to a demand to meet some need. Human functions can be grouped into several categories. Following is the way functions have been categorized by the National Assistive Technology Research Institute (NATRI) staff, accompanied by examples of how special education, assistive technology, and related services may be provided to facilitate functions associated with the categories. This conceptualization is adapted from Melichar's (1978) work to categorize and locate assistive and adaptive devices according to their functional applications.


Functions associated with existence are those responses that are needed to sustain life. These functions include feeding, elimination, bathing, dressing, grooming, and sleeping. Special education services, particularly those for preschool children and those with severe disabilities, may focus on teaching children to perform such functions. Special devices such as button hooks, weighted eating utensils, and combs with long handles may be provided to assist children in performing those functions. Assistance in using such devices also may be provided by occupational therapists.


Oral and written expression, visual and auditory reception, internal processing of information, and social interaction are functions included in the category of communication. Communication aids, speech synthesizers, telephone amplifiers, hearing aids, and the services of speech-language pathologists and audiologists might be appropriate to support communication functions.

Body Support, Protection and Positioning

Some people need assistance to maintain a stable position or support portions of their body. Braces, support harnesses, slings, and protective headgear are useful devices in this functional category, as would the services of a physical therapist. Other medical personnel also may provide supporting services with functions in this category.

Travel and Mobility

Functions in this category include crawling, walking, using stairs, lateral and vertical transfers, and navigating in the environment. Wheelchairs, special lifts, canes, walkers, specially adapted tricycles, and crutches can be used to support these functions. Specialists, such as those who provide mobility training for children who are blind, may be called upon to provide services associated with this category.

Environmental Interaction

The environment can be adapted or the person can adapt to the environment. This category includes functions associated with these adaptations as seen in the performance of many of the activities of daily living, both indoors and outdoors. Examples of functions include driving, food preparation, operation of appliances, accessing facilities, and alteration of the living space. It may be necessary to make a number of modifications to school facilities to accommodate functions in this category. For example, enlarged door knobs, special switches for controlling computers, grabbers to reach items on high shelves, chalkboards and desks that can be raised so that a student in a wheelchair can use them, and ramps to accommodate wheel chairs may be required. Often, assistive technology specialists are called upon to provide help with environmental adaptations.

Education and Transition

Functions in this category include those associated with school activities and various types of therapies and rehabilitation processes. These might include functions such as assessment, special education, learning, creative and performing arts, and preparing for new environments. Special education teachers and regular class teachers, speech-language therapists, rehabilitation counselors, psychologists, and others may be involved in providing direct services to students. In addition, numerous technologies also may be used within the context of schools. Included may be computer assisted instruction, audio instructional tapes, print magnifiers, book holders, and other materials and equipment that can facilitate education.

Sports, Fitness, and Recreation

Functions associated with group and individual play, sports, games, hobbies, and productive use of leisure time are included in this functional category. The services of a person trained in adapted physical education may provide a valuable resource in this area. In addition, there is a wide array of equipment and devices that can facilitate functions in this category, including balls that emit audible beeps so that children who are blind can hear them, specially designed skis for skiers with one leg, Braille playing cards, and wheelchairs for basketball players who cannot walk or run.

Many more examples of services and devices could be provided, but these should be sufficient to illustrate the importance of attending to human functions when planning and implementing special education and related services. It should be apparent that it is more relevant to focus on the functions that a student can perform and those in which difficulty is experienced than to focus on a diagnostic label when planning special education services. Such an orientation enables teachers and those providing related services to more directly address a child's needs.

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Unifying Functional Model

The unifying functional model displayed below has been developed to illustrate the different elements of life associated with a functional approach to special education and related services, including the provision of assistive technologies. When examining this model, note that the items in each box are meant to be illustrative and not all-inclusive.

This is a complex diagram that consists of boxes with text connected by arrows that
	  indicate relationships among the items in the boxes. The boxes are labeled Environment and Context,
	  Functional Demands, Explore Options, Personal Perceptions, External Supports, Personal Resources, 
	  Functional Response, Personal changes, and Evaluation and Feedback. The relationships are
	  explained in the narrative that follows the model.

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An Illustration

To illustrate the elements of the model, their interrelationships, and how the model can apply to special education and the use of assistive technology, let's assume that we have a preschooler, named Ann, who has cerebral palsy. Although she appears to have average intellectual abilities, her speech is almost impossible to understand. Ann's preschool teacher often uses instructional games in class to teach various concepts, such as Simon Says to help children develop their listening skills and learn how to follow directions.

Environment and Context

Let's begin with the box at the bottom of the model, labeled environment and context. The environment we are dealing with is Ann's preschool classroom. The context is that several games are played each week and that the teacher wants Ann to be an active participant.

Functional Demands

The arrow going to the functional demands box indicates that the factors in the environment and their context place demands on all of us. The functional demand coming from Ann's environment is for her to participate in the classroom games, either as a member of the group or as the leader of the group, such as playing the part of Simon in Simon Says.

Explore Options

In preparing to make responses to demands from the environment, people explore their options, as illustrated by the next box in the model. In so doing, they typically assess what their options are for coping with the environmental demand, experiment with several, and make adaptations that will enable them to respond in a constructive fashion to the demand. In Ann's case, she and the teacher might explore options such as letting other students speak for her during the games, using her picture communication board, or using a tape recorder with appropriate prerecorded tapes for each game.

Three variables impact on the exploration of options, as illustrated by the three boxes that are connected to the explore options box with double headed arrows in the model. The double headed arrows indicate that there is considerable interaction among these factors, as illustrated in the next three descriptions.

Personal Perceptions

One's personal perceptions play a big part in exploring response strategies and making a decision about which to accept. For example, some people may, or may not, perceive that a need exists or that they have a problem. Such would be the case when a person with a hearing loss refuses to wear a hearing aid, even though it may help in hearing because the person perceives that it draws negative attention or is a sign of old age. People also have perceptions about the psychological, physical, and monetary costs of different alternatives and their consequences.

Personal Resources

A second factor in considering options when making decisions about appropriate response strategies relates to the personal resources that people have available to them. These relate to their abilities in areas such as physical functioning, cognitive ability, intelligence, motivation, speech, and other personal dimensions which can be used in producing actions.

External Supports

A third factor influencing decisions relates to the external supports a person has available. Supports are resources available to assist individuals in responding to environmental demands. For example, family members can provide both emotional and physical support. Social service agencies can provide supportive services, such as instruction about ways to cope with environmental pressures. Health insurance agencies can sometimes provide financial support for the purchase of assistive and adaptive devices. Special education is another major form of external support, as is the delivery of assistive technology services.

Functional Response

After exploring the enviromental demands in the context of the person's personal perceptions and personal resources and the external supports that are available, the arrow leading to the next box indicates that a response has been selected to cope with the demand. Let's see how all of these areas impact on Ann. In the area of perception, Ann realizes that she has a problem in making herself understood, yet she wants to find a way to participate in the games. In surveying her personal resources, Ann and her teacher conclude that she has the cognitive and physical abilities to participate in the games. In addition, she has a fierce desire to do things for herself. This makes the possibility of another student taking her turn an undesirable option.

In further exploring options, she decides against her communication board because there are 20 other students in the classroom and they would have a difficult time seeing the board while playing the game. In the area of external supports, she and the teacher elect to try a tape recorder and the teacher volunteers to locate a tape and have the tapes recorded with input from Ann regarding the content of each tape.

The functional response is the result of the decision-making that was just described. In Ann's case, this is the use of prerecorded audio cassette tapes that will enable her to be the leader when playing Simon Says.

Personal Changes

As a result of the functional response to the environmental demand, the person usually changes, as represented in the next box in the model. Changes may be dramatic or subtle, depending upon the nature of the environmental demand, the decision making that was done, and the nature of the resources that were expended and the supports provided.

Our student, Ann, has improved her ability to function in her environment by using a tape recorder to participate in educational games. Although she is now able to play the games, the availability of the tape recorder has led her and her teacher to think of other activities in which the tape recorder may be appropriate.

Evaluation and Feedback

Feedback is represented by the arrows emanating from the evaluation and feedback element in the model. Those arrows impact each of the other boxes in the model. Each variable has the potential for being affected by such feedback. With respect to the area of assistive technology for Ann, for example, the use of the tape recorder (a "medium tech" device) may result in the identification of additional problems, such as the limitation that the linear nature of the recording may have on its functional utility (e.g., the recorded messages must be played in sequence). This may trigger a search for an augmentative communication device, such as a "high tech" device like the Speak Easy, that stores recorded words, sentences, or phrases that can be more easily accessed and activated by the user.

Thus, the process represented in the functional model becomes a dynamic one, in which demands constantly change, as do personal perceptions, personal supports, external supports, coping strategies, and examination of alternative solutions. The result is changing functional responses to the environmental demands that lead to personal changes which, in turn, have the potential for changing all of the other factors illustrated in the model.

Interaction of Factors

There are a few more things to notice about the model. Some arrows indicate that some variables impact directly on various model components and activities. These impacts should have been quite apparent in the example with Ann.

Other arrows indicate that there is an influence on the component, but it might not be a strong one or a direct one. For instance, because Ann changed her ability to function, her perceptions have probably changed somewhat. It is possible that her perceptions of her ability to communicate are enhanced through the use of the communication aid and she may be more confident in her ability to interact with her classmates.

There may be an improvement in her personal resources. For example, things she learns as a result of participating in the games will be available to her in the future. Her language skills may improve. Her stamina may improve because she does not have to expend as much physical energy in attempting to make herself understood.

External supports also may be modified, perhaps in more subtle ways. For example, her speech therapist may decide to explore other forms of assistive devices because Ann has demonstrated that she understands how to use devices such as the tape recorder and the Speak Easy and is able to successfully integrate them into her classroom environment. Members of her family may be more encouraged to see the improvement in her ability to communicate and may incorporate the use of the devices in the home, thus improving the quality of life for all concerned.

With both types of arrows, it is important to realize that they not only represent an area of influence, but they also reflect time. The changes that occur, do so over time. The impact may be sudden or it may take a while.

The fact that the model, as presented in this two-dimensional format, represents a "snapshot" of a person's situation at a single moment in time should not be overlooked. As such, it does not reflect that changes are constantly occurring in each component and that these changes have the potential for impacting on the other components and subsequently on the functional responses made by the child.

Personal Variables

The final feature to note in the model is that several boxes have shaded areas. These boxes are those that represent exploring options, personal perceptions, personal resources, and personal changes. These reflect personal variables, while the other boxes represent variables that are often under the control of others.

As we just noted, the model, as presented, is two-dimensional. However, the central focus is the individual child and the decisions that are involved in assisting that child in responding to environmental demands. That process is certainly complex and more than a two-dimensional one.

Source of the Model

The model evolved from more than 25 years of research and development activities by Dr. Joseph F. Melichar (1978). The original model is explained in more detail, with examples of its application to people with disabilities, in an introductory special education textbook (Blackhurst and Berdine, 1993). Since that time it has been modified and revised to reflect the current description that has been provided here.

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Implications of the Functional Model for Assistive Technology Services

The functional model has a number of implications for those who are involved in providing assistive technology services. It helps in the understanding of how a person functions, the factors that are important in making decisions, and how the decisions that are made can impact on the child. It also identifies many of the factors that should be taken into consideration when making decisions about the nature of assistive technology services that are provided to a given student.

It illustrates interrelationships of component factors and their potential for influencing each other. Although the model does not define cause-and-effect relationships, it does help people realize that many factors are involved and that they interact in complex ways.

The model provides direction for those making referrals of children for assistive technology services. Those who make referrals should be aware of the model and its components. Furthermore, they should be encouraged to obtain as much information as possible about the various factors and provide data about them as part of the referral process.

It also can guide assessment and instructional planning activities. By attending to the factors in the model, and others that may be identified, those performing assessments of children who have been referred for assistive technology services can use the model to identify variables that should be evaluated for their potential impact on a child. Assessments of those variables should generate data that can aid in making decisions about the types of assistive technology services that could help children respond successfully to environmental demands.

Research by several of the staff members of NATRI has shown how the model can be used to guide the consideration of assistive technology when planning the individualized education programs (IEPs) for children enrolled in special education programs. Results of this research will be posted on this Web site as they become available.

Several school districts in Kentucky are using the model to guide their delivery of assistive technology services, including screening, assessment, instructional planning, delivery of services, evaluation of their effectiveness and staff development. Reports of that research also will be posted as they become available.

Additional information about the model is available elsewhere. A book chapter provides more information about how the model can be used to guide the delivery of assistive technology services to people with disabilities (Blackhurst & Lahm, 2000), Specific examples of applications in each of the seven functional areas are provided in that resource.

A report explaining how the functional areas and the model can be used to structure multimedia assistive technology instructional programs is available on the report menu of this site. A more detailed description is provided in an article by Blackhurst and Morse (1996).

An article about how to use the model as a framework for aligning technology with transition competencies illustrates another application (Blackhurst, Lahm, Harrison, & Chandler, 1999).

Finally, the functional model is being used by NATRI staff to aid in the conceptualization of several of its studies. For example, the model provides a way to identify variables and processes that will be examined in case studies of assistive technology in schools. The seven functional areas that were described earlier also are being used to categorize reports of effective and ineffective uses of assistive technololgy in the critical incident studies that are being conducted.

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Blackhurst, A. E., & Berdine, W. H. (Eds.), (1993). An introduction to special education (3rd Ed.). New York: HarperCollins.

Blackhurst, A. E., & Lahm, E. A. (2000). Technology and exceptionality foundations. In J. D. Lindsey (Ed.) Technology and exceptional individuals (3rd. Ed., pp.3-45 ). Austin, TX: ProEd.

Blackhurst, A. E., Lahm, E. A., Harrison, E. M., & Chandler, W. G. (1999). A framework for aligning technology with transition competencies. Career Development for Exceptional Individuals, 22 (2), 153-183.

Blackhurst, A. E., & Morse, T. E. (1996). Using anchored instruction to teach about assistive technology. Focus on Autism and Other Developmental Disabilities, 11, 131-141.

Melichar, J. F. (1978). ISAARE: A description. AAESPH Review, 3, 259-268.

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Credits and Disclaimers

A Functional Approach to the Delivery of Assistive Technology Services (© 2001) was prepared for the National Assistive Technology Research Institute by A. Edward Blackhurst, Professor Emeritus, Department of Special Education and Rehabilitation Counseling, University of Kentucky. It may be duplicated and circulated for non-commercial purposes, provided this credit is included.

Support for the preparation of this report was provided by the University of Kentucky and the Research to Practice Division or the Officer of Special Education Programs in the U. S. Department of Education under Cooperative Agreement #H327G000004. The information and conclusions presented in this report do not necessarily reflect the official positions of the funding agencies.

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