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Using a Discrimination Task to Teach Scanning to Severely Physically Impaired Non-Vocal Children (1984)

Using a Discrimination Task to Teach Scanning to Severely Physically Impaired Non-Vocal Children (1984)

©1984, 2013 by Dallas Denny

Source: Denny, Dallas. (1984, 1 May). Using a discrimination task to teach scanning to severely physically impaired non-vocal children. Paper for Dr. Jim Fox, George Peabody College of Vanderbilt University.





Using a Discrimination Task to Teach Scanning

To Severely Physically Impaired Non-Vocal Children


By Dallas Denny

Department of Special Education

George Peabody College of Vanderbilt University

Research Proposal for Dr. James Fox

Special Education 3220


1 May, 1984


Descriptors: augmentative, communication, scan, discrimination learning, non-vocal, cerebral palsy, microcomputer, physical impairment, physical handicap

Independent Variable: Number of squares on CRT screen through which an indicator moves

Dependent Variable: Scores on pre and post tests on an augmentative communication program requiring scanning




Microcomputers can be of use as augmentative communication devices for individuals who are severely motor impaired, non-vocal, and severely retarded. However, these individuals often lack the necessary skills to successfully operate communication software. Brinker and Lewis (1982a, 1982b) have demonstrated that impaired infants can learn to control devices with simple adaptive switches. It is hypothesized that a simple discrimination learning paradigm could be used to teach children one of the concepts necessary to operate an augmentative communication device. A proposal is forwarded for a study to be conducted with three non-vocal, severely handicapped students of a local elementary school. The subjects will be trained to operate an “electronic communication board” (i.e. a computer program which moves an indicator through a variable number of choice points), using a single switch. Switch use will be trained to criterion levels, after which the subjects will be given a pre-test in which they will be asked to select a drawing of a known word from a field of 16 drawings. Then the subjects will be trained, using a discrimination learning paradigm, to correctly select a drawing from fields of lesser numbers of objects. After training, there will be a post-test, and three months later, a follow-up. The design is a multiple probe design; that is, periodic measurements will taken of performance on different phases of training before they are introduced.

The severely physically impaired individual with a communication disorder poses extreme problems to psychologists and educators. Conventional methods of assessment and educational programming, which require an intact and mobile individual, are often useless (Fay, et. al, 1982). Recently, microcomputer technology has been used in various ways to remove barriers in the lives of this population, for example, as augmentative communication aids or environmental control devices (Johnson, 1984). Much of the available software presupposes literate users (Denny, 1984). Unfortunately, some educators are of the opinion that computers have little to offer to physically impaired severely retarded individuals:

Children who are severely physically impaired with uncompromised or minimally compromised intellectual abilities serve to gain significantly from the myriad of benefits that the microcomputer affords.

—Rushakoff & Lombardino, 1983 p. 18

If, however, full advantage is taken of the inherent interactive nature of microcomputers, it becomes apparent that there may be little limit to their potential as educational devices for both nonretarded and retarded individuals. (Naiman, 1983).

Simple non-mechanical communication boards are commonly used by physically impaired individuals; however, such boards impose severe limitations on communication abilities (Fay, et. al., 1982). Electronic devices can serve as communication boards; they have the advantage of requiring much less physical exertion or ability than an actual communication board; typically, they can be operated by a single adaptive switch. The ZYGO communicator, which is marketed by ZYGO, Inc., is such a device. Microcomputers add the advantage of almost infinite adaptability, of speech, sound effects and music, environmental control, record-keeping, and hardcopy.

Normal infants discover that events can be consistently controlled by their behavior (Brinker & Lewis, 1982a). Severely physically impaired children miss many learning and reinforcing events because of their limited ability to interact with the environment and individuals near them. Assessment of the cognitive abilities of such individuals may be made even more difficult by a lack of contingencies between their erratic and sporadic motor movements and co-occurring events. Microcomputers provide a means of providing such contingencies, and have been demonstrated to increase behaviors of hypoactive, retarded infants (c.f. Brinker & Lewis, 1982b).

Brinker and Lewis (1982b) used an Apple II computer to provide such contingencies (mechanical switching of electrical toys); the computer also kept records of the frequency and duration of behaviors (switch closures) of the infants. Tracy (personal communication) and researchers at Peabody College of Vanderbilt University (Warren, personal communication) have attempted to utilize procedures similar to those used by Brinker and Lewis in a process called “Dynamic Assessment.”

If behaviors of severely motor impaired children increase when they are reinforced for those behaviors (and they do) then it would be possible to provide them with a simple discrimination learning paradigm (Mackintosh, 1974). If this discrimination is mastered, then more subtle discriminations can be progressively presented. Discrimination learning can be used for different ends; one possibility is to teach the student to discriminate that reinforcement may occur when an indicator is in a particular position. This is similar to conditions in an operant conditioning chamber when a pigeon is presented with a green (reinforcement condition) or a red (non-reinforcement condition) light. The pigeon eventually pecks at a key at a high rate when the green light is lit, and at a much lower rate when the red light is lit. An example with humans would be a teacher who looks at, smiles at, and talks to a child when she is in her seat, and ignores her when she is out-of-seat. The child eventually learns the reinforcer (i.e. attention) is not forthcoming when she is out of her seat, but is available when she is sitting in it. Eventually, the child spends more time in her seat.

In many augmentative communication programs, an indicator of some sort moves sequentially along a row or through a matrix of possible choices; if the individual selects (closes a switch) during a “window time,”, then a “choice” has occurred. Some, and perhaps many, physically handicapped individuals have a difficult time mastering this “scanning” concept (Hooper, personal communication).

If impaired infants and children can learn that their movements can reliably produce various outcomes, then it should be possible to train them to use that knowledge to operate a computer-based communication device. The concept of “scanning” is a necessary skill for operation of most such augmentative devices, and an empirically based method of teaching it would be useful. The proposed research is an initial attempt to use a discrimination learning paradigm to teach severely physically impaired nonvocal children to indicate choice in an augmentative communication program using a scanning mode.




Subjects will be three students of Harris-Hillman School in Nashville, TN, who have been diagnosed by a physician as severely physically impaired and by a licensed psychologist or psychological examiner as mentally retarded, and who have been unable to consistently demonstrate choice of known objects using a ZYGO-type communication device in a scanning mode. Requisite permissions and consent forms will be obtained from Harris-Hillman School and Vanderbilt University.


Hardware will be a Commodore 64 microcomputer with a disk drive or cassette tape recorder, and a television or monitor. Software will be “All a Board”, an “electronic communication board” which has been developed by the author.

“All a Board” is an augmentative communication computer program which was designed by the author to allow individuals with very severe physical handicaps to communicate their wants and needs to others, using a single switch. It serves the same purpose as any communication board (Silverman, 1980), but requires much less physical ability.

“All a Board” has options which are definable by a teacher or attendant. The number of squares into which the board is divided can be varied from two to twenty-five; five indicator sizes can be selected; and the speed with which the indicator moves from block to block can be changed.

Each student will operate the program by means of a single momentary contact switch. Switches will be especially adapted to the physical limitations of each student. Those students who have not been previously evaluated for switch use by an occupational therapist will be evaluated by a registered occupational therapist.



Selection of Target Words: Teachers of the subjects will be asked to provide a list of twenty objects which each subject can recognize and thirty distractor objects which each subject cannot recognize. Subjects will be shown line drawings of each object and asked if it is a      . The correct name of the object will be used half the time, and a distractor will be used half of the time, on a random basis. Indication will be by whatever means of communication is currently used by the student. Each subject will be trained by the instructor to criterion (significance by the binomial test at the .05 level, two-tailed; c.f. Burghardt & Denny, 1983).

Setting: Testing will occur in a quiet area of the school. For each student, the first four words which meet criteria will be used as target words.

Training in Switch Use: When each student has met criteria, the adaptive switch and the computer will be introduced. An evaluation will be made, and training provided, if necessary, until the students can reliably close their switch. The time required for each student to press the switch will likely vary. Therefore a “window time” will be found for each student by a trial-and-error procedure. Training will end when, upon command, the student produces 8 switch closures within the window time.

Performance Pre-test: Each child will be given a performance pretest, in which the CRT screen will be divided into 25 sections. Plastic transparencies with line drawings of twenty-four distractors and an exemplar chosen randomly from the respective pools will be randomly placed on the screen. The child will be given thirty trials; during each trial, the child will be asked to press the switch when an indicator is in the same section of the screen as is the exemplar word.

Training: The CRT screen will then be divided into two parts, with a blinking indicator moving between the two parts at a slow rate. A transparency of the target word and a distractor word will be placed on either the left or right half of the screen according to a sequence introduced by Fellows (1967). The distractor word will be randomly chosen for each trial from the pool.

The subject will be given 30 trials per day. During each trial, the subject will be asked to close the switch when the indicator is in the same division of the screen as is _____. When the student reaches significance (p<.05, two-tailed), it will not again be presented; when significance is reached for all four words, the screen will be divided into four squares; the target word will be presented with three distractors, and the process repeated. After students have again reached criteria, the screen will be divided into 8 sections, and, finally, 16 sections. Each day, several probe trails (Tawney & Gast, 1984) will be made on sections with greater numbers of squares.

When an incorrect choice is made, the television screen will be blanked for 5 seconds. Upon a correct choice, the subjects will be reinforced with hugs, smiles, and praise from the researcher. Each day, after the training session, the researcher will help the subject “write a story” using a popular educational program.

Performance Post-test and Follow-up: The subjects will receive a post test in which they will again be given thirty trials with the screen divided into 25 sections. Three months after the termination of the study, a follow-up will be done to measure retention.


Data Collection and Agreement

Switch closure will cause the computer to produce audible and visual signals. The effects of switch closure define it; i.e., switch closure is a visual and audible signal produced by the computer. The first switch closure after the instructor asks the child to close the switch when the indicator is in the same part of the screen as is the _____ will be counted as the child’s response. Subsequent switch closures may be noted, but are not part of the formal data collection.

Later, the computer itself will be used to record data; at this time, however, data collection routines are not in place. The author will be the preliminary observer. A second observer will be present on one out of four sessions on the average. Agreement will be calculated by the exact agreement method. Data will not be interval data, but trial data.


Data Analysis

Data will be plotted daily in graphical form on binomial probability paper. Changes in experimental conditions will depend upon performance reaching criterion levels (that is, statistical significance at the .05 level, two-tailed). Data from the probes will be graphed and visually examined in order to see whether generalization occurs.


Hypothesis, Dependent Variable, Independent Variable

In that this is a preliminary investigation, there is not a formal hypothesis. However, it is expected that the ability to run a communication program with a lesser number of squares will generalize. The variable manipulated (independent) will be the number of squares into which the CRT is divided and through which an indicator moves. The variable to be measured (dependent) is the performance of the children on the communication board—i.e., the ratio of correct to incorrect responses.


Experimental Design

Design will be a multiple probe (Tawney & Gast, 1984, Ch. 11). This design is much like a multiple baseline design; however, data are collected non-continuously, or in probe sessions or probe trials, on behaviors which have not yet been intervened upon. This design will allow the measurement of generalization to boards with greater number of squares before training occurs.



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