ADAPTED PHYSICAL ACTIVITY QUARTERLY. 1994, 11. 347-358 @ 1994 Human Kinetics Publishers, lnc. Using the Constant Time Delay Procedure to Teach Task-Analyzed Gross Motor Skills to Individuals With Severe Intellectual Disabilities Jiabei Zhang, Michael Horvat, and David L. Gast The University of Georgia It is imperative that teachers utilize effective and efficient instructional strategies to teach task-analyzed gross motor skills in physical education activities to individuals with severe disabilities. The purpose of this paper is to describe the constant time delay procedure, which has been shown to be effective in teaching task-analyzed fine motor skills in daily living and safety activities. In this article, guidelines are presented for teaching task-analyzed gross motor skills to individuals with severe intellectual disabilities. These guidelines are based on a review of the constant time delay procedure reported in the special education literature and current research being conducted by the authors. Individuals with severe disabilities generally have difficulty acquiring motor skills because of difficulty in speech, language, and cognition, as well as accompanying sensory or perceptual deficits (Bishop & Horvat, 1990). In spite of these difficulties, it has been demonstrated that learning can occur if the materials to be learned are presented in a systematic manner. It is important that effective and efficient instructional strategies that can be easily replicated by others be identified for teaching students with severe disabilities. The two most common procedures for teaching gross motor skills to this population are the increasing prompts hierarchy procedure and the decreasing prompts hierarchy procedure (Dunn, Morehouse, & Fredericks, 1986; King & Mace, 1990). The increasing prompts hierarchy procedure, also referred to as the system of least prompts procedure (Wolery, Ault, & Doyle, 1991), provides the learner with the opportunity to perform the target skill independently on each trial before a hierarchy of prompts is introduced that will assist the learner in performing the skill. This procedure includes at least three levels (i.e., the independent level and two prompt levels). The first level provides the learner the opportunity to respond to the natural cue without prompts. If the student gives an incorrect The authors are with the Departments of Physical Education and Special Education, Physical Education Building, The University of Georgia, Athens, GA 30602-365 1. Address correspondence to Michael Horvat.
348 Zhang, Horvat, and Gast response or does not respond to the natural cue alone, a prompt, such as a teacher model, is provided to assist the learner. If the student still does not respond or responds incorrectly, the instructor presents a more intrusive prompt, such as physical assistance, which ensures a correct response (Wolery et al., 1991). Although effective, the increasing prompts hierarchy procedure frequently results in students making numerous errors before reaching criterion (Wolery & Gast, 1984). It also results in an increase in instructional time. In physical education, this is commonly seen in an activity such as swimming where the teacher asks the student to perform a stroke (independent level), demonstrates the stroke (Prompt Level I),-and then provides assistance (Prompt Level 2) if the student does not respond correctly. The decreasing prompts hierarchy procedure, also referred to as most-toleast prompts hierarchy (Wolery et al., 1991), does not provide the learner with the opportunity to perform the skill independently on each trial; rather a prompt that guarantees the correct response is presented first. After a set number of successful trials with this prompt level, a less intrusive prompt is introduced. The first prompt level is the most intrusive, such as physical assistance. If the learner responds correctly at this level for three consecutive trials, the second level of assistance is presented, such as a teacher model. If the learner responds correctly for three consecutive trials with modeling, the student is given the opportunity to perform the skill without assistance other than natural cues. Initially, the learner comes under the control of the teacher's prompts to initiate and complete the response sequence rather than under the natural cue for independent responding. Over successive trials the control is transferred to a less intrusive prompt and finally to the natural cue alone. One possible drawback of this procedure is that students may become prompt dependent (Miller & Test, 1989). Another disadvantage is that students may take a long time to reach criterion since they are "locked in" to the prompt hierarchy and do not have the opportunity to demonstrate independent performance. Commonly in a physical education skill such as swimming this procedure begins with physical assistance (Prompt Level 1) to generate a correct response followed by a model (Prompt Level 2) of the correct response, and finally a task direction (natural cue) verbally. An alternative to these two procedures is the constant time delay (CTD) procedure, one of the newer teaching strategies. This procedure has been shown to be effective in teaching task-analyzed fine motor skills in daily living and safety activities (Schuster, Gast, Wolery, & Guiltinan, 1988; Winterling, Gast, Wolery, & Farmer, 1992). However, application of the CTD procedure in teaching task-analyzed gross motor skills has not been discussed in the published literature of physical education. The purpose of this paper is to (a) review the studies on the CTD procedure in teaching task-analyzed fine motor skills in daily living and safety activities, (b) describe the CTD procedure in teaching task-analyzed gross motor skills in physical education activities, and (c) provide a model for teaching gross motor skills using the CTD procedure. Studies on CTD in Teaching Task-Analyzed Fine Motor Skills The CTD procedure is a response-prompting strategy that results in near errorless learning by inserting a fixed amount of time between the points when the teacher
Constant Time Delay Procedure 349 presents the target stimulus and the controlling prompt (Wolery et al., 1991). It is a modification of the progressive time delay procedure, in which increasingly more time is inserted between the target stimulus and the controlling prompt over successive trials or blocks of trials. The progressive time delay procedure, as initially described by Touchette (1971), involved systematically varying the temporal interval between the target stimulus and the controlling prompt, in order to pinpoint the moment that adolescents with severe disabilities came under the control of a new stimulus. The CTD procedure is a response-prompting strategy in which the teacher fades her assistance by systematically inserting a fixed amount of time between the presentation of the target stimulus and the delivery of the controlling prompt (Wolery et al., 1991). The target stimulus refers to something that cues the individual to perform the target skill, and the controlling prompt refers to the teacher's assistance that ensures the student's performance of the correct response. The goal of the procedure is for the learner to make the correct response within the delay interval if she is sure of the correct response, or to wait for teacher assistance if she is unsure of the correct response. Thus, the procedure not only provides the student with the opportunity to make independent responses but also minimizes errors if the student waits for the controlling prompt. Initially, correct responses both before and after the prompt are reinforced. In the special education literature, it has been shown that learners consistently give more comct responses before the prompt with each successive session until students reach criterion by performing 100% of their responses before delivery of the controlling prompt. For example, the use of the CTD procedure in teaching fine motor skills in daily living activities was studied by Schuster et al. (1988). In this study, the effectiveness of a 5-s CTD procedure with a verbal prompt plus modeling as a controlling prompt on teaching three task-analyzed food preparation skills (i.e., making a sandwich with 21 steps, boiling a boil-in-bag with 23 steps, and baking canned biscuits with 23 steps) to four adolescents with moderate intellectual disabilities was evaluated with a multiple probe design across skills. Results indicated that the CTD procedure was effective in teaching all students to perform all skills. The skills were maintained with at least 85% accuracy over a 3-month period after teaching. The percentage of errors across all skills and students was less than 9%. The CTD procedure has also been used to teach operating a dryer and washing machine to individuals with intellectual disabilities (Miller & Test, 1989); various independent living skills to individuals with moderate intellectual disabilities (Wolery, Ault, Gast, Doyle, & Griffen, 1990); recipe-following skills to individuals with moderate intellectual disabilities (Schuster & Griffen, 1991); self-feeding skills to children with severe to profound disabilities (Collins, Gast, Wolery, Holcombe, & Leatherby, 1991); various self-care skills to individuals with moderate to severe intellectual disabilities (Hall, Schuster, Wolery, Gast, & Polyle, 1992); first-aid skills to students with moderate to severe disabilities (Gast, Winterling, Wolery, & Fanner; 1992); and safe handling of broken materials by high school students with moderate disabilities (Winterling et al., 1992). The CTD procedure can be effective in teaching a variety of daily living and safety skills to individuals with moderate to severe intellectual disabilities. Furthermore, the CTD is an efficient procedure based on rapid learning with an error rate that is generally less than 10% (Wolery et al., 1991).
350 Zhang, Horvat, and Gast A few studies have compared the CTD procedure to other teaching strategies. Ault, Gast, and Wolery (1988) compared the CTD procedure to the progressive time delay procedure in teaching sight word reading to three elementaryage students with moderate intellectual disabilities. In this investigation both procedures were effective and were considered to be equally efficient. Generally, the CTD procedure is considered to be simpler to use than the progressive time delay procedure because the same prompt delay interval is used throughout instruction (Schuster et al., 1988). The CTD procedure has been found to be equally effective and more efficient than the increasing prompts hierarchy procedure in teaching task-analyzed purchasing skills (McDonnell, 1987) and selfhelp skills (Schoen & Sivil, 1989). McDonnell (1987) indicated that students who received the CTD procedure made fewer errors in reaching the instructional criterion than students who received the increasing prompts hierarchy procedure. The CTD procedure has also been compared to the decreasing prompts hierarchy procedure in teaching task-analyzed banking skills (McDonnell & Ferguson, 1989) and laundry skills (Miller & Test, 1989). Both investigations found the procedures to be effective, but McDonnell and Ferguson (1989) found the decreasing prompts hierarchy procedure to be more efficient, while Miller and Test (1989) found the CTD procedure to be more efficient. In studying the decreasing prompts hierarchy procedure, Miller and Test (1989) found that students came under stimulus control of the teacher's physical prompts prior to initiating the next step in the chain, which likely slowed the transfer of stimulus control to the natural stimulus. That is, students may have become prompt dependent. The CTD procedure provided the students the opportunity to make an independent response on each trial before the delivery of the teacher's prompt, thus making the CTD procedure more efficient than the decreasing prompts hierarchy procedure. Describing CTD in Teaching Task-Analyzed Gross Motor Skills The CTD procedure can be used in teaching gross motor skills in physical education settings. For example, the objective for a particular student is to shoot a basketball. During initial instructional trials, a zero-second delay procedure (by which the task direction and the controlling prompt are presented simultaneously), is employed to help the student learn the correct responses. On each zero-second delay trial, the teacher presents the individual with a task direction, such as "Show me how you can shoot the ball." Following the task direction, the controlling prompt (e.g., physical assistance) is immediately provided on each step of the task analysis. That is, the student will not have the opportunity to perform any of the steps independently. After several zero-second delay trials (5-10, depending on the learner), all subsequent instructional trials will employ a constant delay interval, for example, inserting a 4-s delay interval between the presentation of the target stimulus and the delivery of the controlling prompt, to fade the teacher's prompt. On each 4-s delay trial, the teacher will give the task direction and then wait 4 s (i.e., count silently "1001," "1002," etc.) before providing the controlling prompt. Upon initiation of the student'sresponse on the first step of the task analysis,
Constant Time Delay Procedure 351 the individual has a designated amount of time to complete the step (e.g., 4 s, depending on the response requirements). If the individual makes no response or an incorrect response, the teacher provides the controlling prompt. The 4-s delay interval will begin immediately for the next step of the task analysis after the teacher acknowledges the student's response (i-e., provides descriptive verbal praise or error correction). This delay period between the completion of one step and the presentation of the prompt on the next step continues until all steps of the task analysis are completed. The 4-s delay trials continue until the individual reaches criterion as stated in the instructional objective (e.g., 100% unprompted correct responses over three consecutive teaching sessions). The selection of the 4-s delay was predicated upon task and student characteristics. Other investigators have used 2 s in teaching snack purchase skills (McDonnell, 1987) to 5 s for food preparation (Schuster et al., 1988). With a 4-s CTD procedure in which the controlling prompt is the teacher's model, the learner's responses on each step are recorded according to one of five possible response categories: (a) unprompted corrects, initiating the step within a 4-s interval and correctly completing the step within the designated time; (b) prompted corrects, correctly completing the step within the designated time following delivery of the controlling prompt; (c) unprompted errors, initiating the step within the 4-s interval but completing the step incorrectly within the designated time (topographic error), not completing the step within the designated time (duration error), or completing a step out of sequence within the designated time (sequence error); (d) prompted errors, not initiating or completing the step following the controlling prompt; and (e) no-response errors, making no response after delivery of the controlling prompt within the designated time. Note that no-response errors are not possible if the controlling prompt is full physical assistance. All correct responses, prompted and unprompted, are initially reinforced with descriptive verbal praise. Tangible reinforcers can be paired with the delivery of the verbal praise for some students. When unprompted errors occur on a step of the task analysis, the teacher interrupts the response, verbally states, "Wait, let me help you if you don't know," and then provides the controlling prompt. When prompted and no-response errors occur, the teacher withholds the "reinforcement" and evaluates the consequences that follow correct responses. Similarly, the teacher should evaluate the reinforcing value of the skill that is being taught. Teaching Gross Motor Skills Using CTD The CTD procedure can be used to teach task-analyzed gross motor skills to students with severe intellectual disabilities. The principle steps of the procedure, based on the success of this investigation and others, include (a) identifying the target skill, (b) task analyzing the target skill, (c) identifying the target stimulus, (d) selecting the controlling prompt, (e) teaching the learner to wait if necessary, (f) determining the number of zero-second delay trials, (g) selecting the length of the delay interval, (h) deciding on the consequences for responses, (i) designing the data collection sheet, and (j) implementing and adjusting the program based on student performance data.
352 Zhang, Horvat, and Gast Principle Steps Identifj, the Target Skill. The first step is to identify the target skill or motor behavior that is to be taught using the CTD procedure. As a general rule, target skills should be selected that are chronologically age appropriate and will facilitate the learner's integration into the community. That is, a skill should be chosen that is consistent with peer group interests in order to maximize independence and participation in recreational and community-based activities (Eichstaedt & Lavay, 1992). The underlying assumption is that the acquisition of gross motor skills will be beneficial to individuals with severe disabilities by increasing participation in community and home-based settings. For example, basketball shooting is an appropriate target skill for an adolescent with severe intellectual disabilities because it is an activity in which his chronological age peers frequently engage in community settings. Task Analyze the Target Skill. The second step is to break down the target skill into a series of meaningful steps, a process known as task analysis. The steps are presented in order, from the first step to be learned to the last step of the sequence. Each step should be observable and measurable. The number of steps will vary depending upon the individual's capabilities and experience as well as the difficulty of the task. In general, less experience and greater severity of the disability as well as task difficulty require that the skill be broken down into more steps. Figure 1 includes an example of a nine-step task analysis for shooting a basketball (Whelton & Taylor, 1988) that may be suitable for students with severe intellectual disabilities: (a) pick up the basketball with both hands, (b) stand behind the foul line, (c) spread feet about shoulder width, (d) place one hand under the ball while balancing the ball with the other hand on the side, (e) bend the knees slightly, (f) raise the ball slightly above the head, (g) focus the eyes on the rim, (h) extend the knees upward, and (i) extend the arms while simultaneously releasing the ball in the direction of the basket (Figure 1). Identify the Target Stimulus. The third step is identifying the target stimulus that is used to cue the student that it is time to perform the target skill. In task-analyzed skills, the target stimulus includes the task direction and the completion of each preceding step. The task direction signals the individual to initiate the first step of the task analysis. The stimulus that cues the individual to initiate the remaining steps is the completion of the immediately preceding step. The teacher can provide a target direction or an arranged cue in the natural environment that signals that it is time to respond (Wolery et al., 1991). For example, in free-throw shooting, the teacher can provide a task direction by saying, "shoot the ball," or can place a basketball on the free-throw line. Select the Controlling Prompt. The fourth step is to identify a controlling prompt or a level of assistance that will ensure a correct response when the assistance is given (Wolery et al., 1991). Modeling can be selected as a controlling prompt if it consistently results in the learner performing the skill. The majority of previous studies that taught daily living or safety skills to students with severe disabilities used verbal direction plus modeling as the controlling prompt. In these studies, all students were able to imitate behaviors designated in the task analysis. However, a controlling prompt of verbal direction plus physical guidance may be needed when teaching individuals with more severe disabilities who cannot consistently or completely imitate a step of a task-analyzed gross motor skill.
354 Zhang, Horvat, and Gast response. This is accomplished by presenting the student with a task that she cannot perform unless she waits for a prompt. In teaching free-throw shooting, the teacher can use wait training by identifying a series of task directions requiring single motor responses that the individual is unable to perform without assistance. For each single response, the teacher provides the task direction that the student does not understand, and then waits for the designated interval (e.g., 4 s) before delivering the controlling prompt. Initially the student may have to wait only 1 s before the teacher delivers the prompt. However, over successive trials or blocks of trials (e.g., five trials) the teacher increases the delay interval by 1 s until the 4-s wait time is achieved. Correct wait responses are positively reinforced. At any time when the individual does not wait for a prompt, the teacher interrupts the response and says, "No, wait for me to help you if you do not know," withholds the reinforcer, and then Dresents the next trial. This is continued until the student demonstrates the appropriate waiting ability for a minimum of three consecutive trials at 4-s intervals. Determine the Number of Zero-Second Delay Trials. Zero-second delay trials refer to when the target stimulus and the controlling prompt are presented simultaneously. Several zero-second delay trials are conducted prior to presentation of the CTD trials. There is no set number of zero-second delay trials that should be conducted. The number has ranged from 1 trial to several sessions of 10 trials. The following general rules should be followed in determining an appropriate number of zero-second delay trials: (a) zero-second delay trials can be increased when more than one step of task analysis is being taught on a single trial, (b) an individual with more severe disabilities may need more zero-second delay trials (e.g., 10-20), and (c) an individual with less experience with the CTD procedure may need more zero-second delay trials. The single most important criterion to use before moving to the constant delay trials is the student's waiting for the controlling prompt with 100% accuracy. For example, when the basketball shooting skill is being taught, 8-12 zero-second delay trials would be appropriate because the skill is task analyzed into nine steps for a more severely involved individual who has little or no experience with the skill or the CTD procedure. Select the Delay Interval Length. The unique characteristic of the CTD procedure, compared to other response-prompting strategies, is that the controlling prompt is faded on a time dimension. The teacher must determine how many seconds should be inserted between the presentation of the target stimulus and the delivery of the controlling prompt. When task-analyzed skills have been taught, delay intervals have ranged from 2 s in teaching snack purchase skills (McDonnell, 1987) to 5 s in teaching food preparation skills (Schuster et al., 1988). Task and student characteristics must be considered in determining the length of delay interval (Wolery et al., 1991). For example, a 4-s delay interval may be appropriate in teaching free-throw shooting or other gross motor skills to most students with severe intellectual disabilities. A longer delay interval between steps (e.g., extending knees upward and shooting the ball to the net) may interrupt the fluency of the skill. Determine the Consequences for Responses. On each step of a task analysis, there are five types of responses a student can make when using modeling as a controlling prompt and four types of responses when using physical assistance
Constant Time Delay Procedure 355 as the controlling prompt. Prior to starting instruction the teacher should know how he is going to respond to each type of response. These teacher responses are referred to as consequent events (Wolery et al., 1991). When free-throw shooting is taught with physical guidance as the controlling prompt, both unprompted and prompted corrects can be reinforced with descriptive verbal praise with an additional reinforcer delivered for unprompted corrects (e-g., tokens or other tangible reinforcer). The objective of the CTD procedure is to get the student to increase the number of unprompted correct responses, which represent independent performance. Differentially reinforcing unprompted and prompted corrects facilitates a student's independent responding. Only unprompted corrects are counted toward criterion performance. A typical consequence for an unprompted error is the teacher interrupting the response and saying, "No, wait for me to help you if you don't know," followed by the delivery of the controlling prompt. Errors made after the prompt (prompted errors) result in full physical assistance without comment from the teacher. If unprompted errors exceed 25% of the task analysis steps attempted in a single instructional session, it is recommended that the student be taught to wait for the prompt. Design the Data Collection Sheet. The CTD procedure data should be collected at each session. The data collection sheet should contain (a) situational information, including the student's name, date, session number, and target skill; (b) performance data on the student's responses on each step of the task analysis; and (c) summary information, including the number and percent of each type of response (Tawney & Gast, 1984). Figure 1 includes a sample data sheet for teaching free-throw shooting with the CTD procedure. Implement and Adjust the Program. After completing the preceding steps, the teacher will be ready to initiate instruction by first conducting a series of zero-second delay trials, then conducting the fixed-second delay trials until the student reaches the instructional criterion. The teacher should monitor progress by graphing the data after each session. With the CTD procedure, both unprompted and prompted corrects are usually graphed and analyzed. Wolery, Ault, and Doyle (1991) summarized three types of data patterns with the CTD procedure. For teaching free-throw shooting, the ideal data pattern is shown in Figure 2a, in which the average number of unprompted corrects steadily increases while the average number of prompted correct responses steadily decreases. Some data patterns may emerge indicating a need to modify the program. For example, the average number of unprompted corrects may remain low while the average number of prompted corrects stays high for several consecutive sessions. This data pattern indicates that the individual is waiting for the prompt and is not attempting to respond before the prompt (Figure 2b). Another common data pattern is when 25% of the steps attempted are prompted errors. In this case, the teacher should evaluate the consequences that are delivered after correct and incorrect responses. Typically there is a need to identify a new reinforcer. To encourage the individual to respond before the prompt, the teacher should differentially reinforce unprompted and prompted corrects. That is, the teacher should provide more reinforcement for unprompted corrects than for prompted corrects. A third data pattern that may emerge is when both unprompted corrects and prompted corrects remain low for several consecutive sessions. This data pattern indicates that the individual is making a high percentage of incorrect
Average 9 Number 8 ofcarect 7 Steps 6 5 4 3 2 1 0 Average 9 Number 8- of Correct 7- Steps 6-5 (a) Data Pattern with Expected Learning Baseline CTD 0" 4" 4" 4" 4" 4" 1 2 3 4 5 6 7 8 9 Sessions (b) Data Pattern with Waiting for Prompts - 4-3 - 2 - Baseline CTD 0" 4" 4" 4" 4" 4" Zhang, Horvat, and Gast Average 9- Number 8- of Correct 7 - Steps 6-5 4 3 2-1 2 3 4 5 6 7 8 9 Sessions (c) Data Pattern with Making High Errors Baseline CTD 0" 4" 4" 4" 4" 4" 1 2 3 4 5 6 7 8 9 Sessions Figure 2 -Three types of data patterns with the constant time delay procedure. Unprompted corrects are denoted by triangles and prompted corrects are denoted by circles. CTD = constant time delay procedure. 0" = zero-second delay. 4" = 4-s delay.
Constant Time Delay Procedure 357 responses (Figure 2c). If the student is making a high percentage of unprompted errors (e-g., 25% or higher), the teacher should use wait training. If the student is making a high percentage of prompted errors or no-response errors, the teacher should reconsider the controlling prompt and the reinforcers. Summary The CTD procedure is a response-prompting strategy that can be used to teach task-analyzed gross motor skills in physical education and recreation activities to individuals with intellectual disabilities. In this procedure the teacher fades assistance by systematically inserting a fixed amount of time between the presentation of the target stimulus and the delivery of the controlling prompt. In recent years, the CTD procedure has been shown to be effective in teaching taskanalyzed fine motor skills in daily living and safety activities to individuals with disabilities. Applications of this procedure in teaching task-analyzed gross motor skills in physical education activities are not evident in the literature. It is recommended that teachers follow 10 steps when using the CTD procedure: (a) identify the target skill, (b) task analyze the target skill, (c) identify the target stimulus, (d) select the controlling prompt, (e) teach the student to wait for the prompt, (f) determine the number of zero-second delay trials, (g) determine the length of delay interval, (h) decide on the consequences for each type of response, (i) design the data collection sheet, and (i) implement and adjust the program based on the graphed data. If the effectiveness of the CTD procedure is replicated in teaching task-analyzed gross motor skills in physical education activities, teachers will have a new teaching strategy to use with students with intellectual disabilities. In special education, teachers of students with mild, moderate, and severe intellectual disabilities have found the procedure effective with a variety of skills and equally efficient or more efficient than other teaching procedures on such variables as trials, errors, and instructional time to criterion. It is hoped that this article will stimulate interest in using the constant time delay procedure to acquire gross motor skills and will encourage research on this procedure. References Ault, M.J., Gast, D.L., & Wolery, M. (1988). Comparison of progressive and constant time delay procedures in teaching community sight word reading. American Journal of Mental Retardation, 93, 44-56. Bishop, P., & Horvat, M.A. (1990). Shaping behaviors in severely handicapped: An effective instructional strategy. In R. French & B. Lavay (Eds.), Behavior management in adapted physical education (pp. 264-270). Kearney, NE: Educational System Associates. Collins, B.C., Gast, D.L., Wolery, M., Holcombe, A., & Leatherby, J.G. (1991). Using constant time delay to teach self-feeding to young students with severejprofound handicaps: Evidence of limited effectiveness. Journal of Developmental and Physical Disabilities, 3(2), 157-179. Durn, J.M., Morehouse, J.W., & Fredericks, H.D.B. (1986). Physical education for the severely handicapped: A systematic approach to a data based gymnasium. Austin, TX: PRO-ED.
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