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The Use of Microcomputers as Augmentative Communication Devices (1984)

The Use of Microcomputers as Augmentative Communication Devices (1984)

©1984, 2013 by Dallas Denny

Source: Denny, D. (1984). The use of microcomputers as augmentative communication devices for retarded and nonretarded persons‑‑ suggestions for improvement of selection strategy. Seventeenth Annual Conference on Research and Theory in Mental Retardation and Developmental Disabilities, Gatlinburg, TN, March.




The Use of Microcomputers as Augmentative Communication Devices for Retarded and Nonretarded Persons

Suggestions for Improvement of Selection Strategies

Dallas Denny

Greene Valley Developmental Center Greeneville, TN




For persons with severe motor impairments which limit their ability to move as well as to speak, computers are of importance as communication aids. However, computer-based communication devices have heretofore been expensive and often crude. The proliferation of reliable, low-cost personal computers has solved the hardware problem, but communication ware is frequently inadequate or inefficient.

Most communication programs presuppose literacy. However, the majority of physically handicapped mentally retarded persons are non-literate and are unable to utilize such programs. For this population, the computer should serve as an electronic communication board with the additional capabilities of providing training, entertainment, and control of devices in the environment.

Existing programs give literate individuals the ability to select words, phrases or sentences and concatenate them to form written English mess ages. The majority utilize a linear scanning direct-selection mode. These programs can be frustrating to use because of long waits due to limitations inherent in their design. There are a number of strategies which serve to decrease the waits and allow more extensive vocabularies, but communication aids, especially those utilizing only a single switch, remain slow and limited. Alternate selection strategies such as the binomial search and encoding allow greater speed of communication and should be more thoroughly explored.

Today’s home computers are capable of supporting applications programs which use various base search strategies. “Six Bits,” which was written for the Commodore VIC-20 computer, utilizes a binomial search strategy to select individual letters from a display. “Fifth Base,” a program under development for the Commodore 64 computer, uses a base 5 search strategy to select from a user-definable list of over 2500 words. “All A Board” is an electronic communication board for the VIC-20 computer.

Many persons with a wide variety of handicapping conditions are unable to speak. Those with good physical mobility can learn to effectively use American Sign Language, pencil-and-paper, portable typewriters, or other communication aids or systems. However, the severely physically involved, non-vocal person—for instance, children with cerebral palsy, stroke victims, and those with degenerative neurological or muscular diseases, may lack the voluntary control to use even a lap board with pictures drawn on it. For those individuals who have the ability to reliably move, however slightly, any single part of their body, an electric or electronic device can be used to augment their communication. Of these types of devices, by far the most versatile are computer-based.

While computer-based augmentative communication devices which are state-of-the-art, custom-made, or in limited-production are available to those who can afford them, there is a need for quality communications software which will run on inexpensive microcomputers which are readily available from mass-market distributors such as K-Mart and Sears.

There are a number of reasons for this. First, support for the custom-based communication device may be suddenly withdrawn; when a hardware problem arises, parts and service may be simply unavailable. Or, if they are available, the equipment may have to be mailed away for repairs; either way deprives the individual of the device. Secondly, as the needs of the user change, for instance, as cognitive abilities are lost during a degenerative process, the built-in software may not be capable of being changed to suit these new needs. Thirdly, updates and enhancements, or even minor modifications of the equipment or software may require factory service.

Microcomputers, on the other hand, are available across the counter in most cities. Many are inexpensive enough that a backup unit can be purchased, should equipment failure occur. Software is provided on tape, disk, or ROM pack, and is easily transported—updates can be mailed. These microcomputers usually have a built-in BASIC language which is to some degree similar across machines. If software is not copy-protected, it can be easily modified by an accomplished BASIC programmer.

With the idea of searching for an inexpensive computer-based communication device—one which cost $1000 or less, Dr. William Tracy and I ordered and examined the 1982-1983 catalogs of a number of major suppliers of communication products (Zygo, Prentke-Romich, Telesensory). In the price-range specified, versatile microcomputer-based communication aids were not readily available from these suppliers. Typically, communication aids in this price range were electric, rather than electronic. Of course, this may have reflected lack of time to introduce such products for a relatively new technology.


Desirable Characteristics of Communication Software

In designing communications software, the individual needs of the non-vocal person must be addressed in the context of the communication situation. Where will communication take place, and what information must be conveyed? Is portability of the system necessary?

A careful assessment must be made of the ability of the person to operate adaptive switches. Can the individual point to any point in a rectangular matrix? Can two switches be used, or must the program be operated by input from a single switch?

Also, the complexity of operation must be within the cognitive abilities of the individual, but should take full advantage of those abilities. For instance, persons who are highly literate should be able to construct complete sentences in correct grammatical form, and to edit those messages, much as text is edited in a word processor. Those who are non-literate or pre-literate should not be required to recognize words, but the software should provide for inclusion of words which may be learned.

Within these constraints, the need is to provide software which will enable the individual to communicate as effectively as possible as rapidly as possible, with the least possible cost.

If possible, the software should accommodate changes in the functioning ability of the individual—for instance, increase of motor control as the result of physical therapy, or loss of language ability due to degeneration.

And finally, the software should take advantage of the programmability and versatility of the computer as much as possible—by this, I mean that use as an alarm device, environmental control, hardcopy, entertainment, and speech options should be available.

On top of this, it would be convenient if provisions were made for educational activities to be carried on through the familiar communication program (with, of course, record-keeping by the computer.)


Software for Literate Persons

The majority of existing communications software presupposes high cognitive functioning, and especially the ability to read or recognize words, or to use abstract symbols. The ideal for this type of software is to approximate as closely as possible the speed of normal conversation. Various strategies are used to allow rapid retrieval of stored messages or construction of new messages from individual letters or stored words and phrases.

Vanderheim (1976) characterized modes of electronic, gestural-assisted communication. These are the following:

Scanning modes—choices are indicated on a display and an indicator moves along in a linear fashion. A switch or switches are pressed during select “window times,” and selection is made. An attempt may be made to arrange choices by frequency of usage, for instance, by arranging letters in the alphabet by frequency of usage. Or, letters may be arranged in a rectangular matrix and two presses—one for the x-axis, and one for the y-axis—made. There may be multiple paging, with the first selection or selections calling different displays. The indicator can be made to move in a non-linear fashion, typically accelerating as it moves. If sufficient motor control is present, analog, rather than digital switches can be used, and the indicator made to move in along the display in a fashion similar to a tachometer moving as an engine is raced with the accelerator petal.

Encoding— As defined by Vanderheiden (1976), is “a technique . . . in which the desired choice is indicated by a pattern or code of input signals, where the pattern or code must be memorized or referred to on a chart.” An example of an encoding strategy is Morse code.

Direct selection—the user directly selects the desired choice—most efficient of the three (Silverman, 1980).

Binomial selection—The pool of available choices is divided into two equal parts; a direct selection is made of the part which contains the desired choice, and the half which does not contain the choice is eliminated, as if playing twenty questions. The remaining pool is divided in half again, and selection again occurs. What is unique about this method is that the size of the pool increases exponentially with the number of selections.


Six Bits

2^1 = 2

2^2 = 4

2^3 = 8

2^4 = 16

2^5 = 32

2^6 = 64

2^7 = 128

2^8 = 256

2^9 = 512

2^10 = 1024


Base 5 selection—discards four-fifths (80%) of pool at any one time.

5^1 = 5

5^2 = 25

5^3 = 125

5^4 = 625

5^5 = 3125

5^6 = 15525


Thus, five presses of a single switch can select any single item from a pool of over 3000 words, phrases, or sentences. It is not necessary to memorize which word is in which position, because words and phrases can be alphabetized.

Table (Click to Magnify)

The Use of Micromputers (Table)

Software for Nonliterate and Preliterate Persons

Electronic communication board

Digression on Base Searches

A long-known and efficient method of selecting a unit from a field of any size is the binomial search technique. A field if repeatedly divided in half and the yes/no question “Is the desired information in this half of the field’?” asked. Each answer requires only 1 bit of information, but allows half of the field to be discarded. Eventually, all information but that desired has been eliminated; selection takes place by repeatedly discarding unwanted information. Effective playing of the child’s game “Twenty Questions” requires use of the binomial search technique.

The major advantage of the binomial search technique is that the size of the field from which a single unit can be selected increases exponentially as a power of two when the number of yes/no questions asked increases arithmetically Answering four questions results in selection from a field of 2^4 or 16 items; answering six questions results in selection from a field of 2^6 or 64items; and answering eight questions results in selection from a field of 256 items. Ten questions increases the size of the field to 1024 items, and twenty questions to 1,048,576.

Some electronic communication devices for individuals with handicaps have been based on the binomial search technique. For instance, six presses of a single switch have been used to select up to 64 alphanumeric characters, punctuation marks, special symbols, or combinations thereof. The advantage of such a device is its speed. While it is relatively unparsimonious in the number of presses required for each selection, there is no need to wait for an indicator to reach a desired character, as in a scanning-based device, or to input more than one type of symbol per switch, as with Morse code. With a single switch and a yes/no cycle time of three seconds, it would take eighteen seconds to select a symbol in a worst-case situation. To increase the speed of the selection, letters and symbols can be arranged in the display in order of frequency of occurrence, or words, phrases, or sentences can be substituted for single characters. Practically speaking, however, an individual can select characters as fast as the switch can be closed six times. Obviously, user fatigue is an important factor in selection of a communication device utilizing the binomial search technique.

It is possible to conduct searches with bases other than the binomial. In a base three search a field is repeatedly divided into thirds and the unwanted two thirds of the field discarded with each selection. As the size of the base of the search increases, the size of the field possible to search with a fixed number of presses increases, again exponentially, as a function of the base of the search. Five presses of a switch in a base 2 (binomial) search selects from a field of 32 items, five presses in a base 3 search selects from a field of 243, and five presses in a base 6 search selects from a field of 7776. Delay time increases with size of the base, but in a linear fashion. With the three second time mentioned above, and in a worst-case selection, it would take 216 seconds to select any one of 7776 items with a base 6 search.

In a communication device such as outlined above, there may be several thousand possible selections. Memorization of such a large field is not practical. Some method of knowing where to branch to in the selection process must occur. For instance, alphabetic selections can be alphabetized, numeric entries arranged in ascending or descending order, and some memonic systems can be used to arrange non-alphanumeric symbols.

For any literate individual capable of operating a single switch, it is possible to find the best base of search/number of questions/size of field. To do so, it should first be determined how large a field is needed in order to include everything the individual needs or wants to communicate to others, with the understanding that the larger the field, the more presses will be required. Once this is determined, then a table can be devised showing required presses versus size of base. Some individuals will obviously want or need larger fields than others, and if they are willing to expend the effort to activate the switch one or two more times, their wishes should be adhered to, within practical limitations of equipment.