Commentary: the environment as a source of variability: implications for research with individuals who have autism.
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Biomedical subjects
Publications and source records attributed to M Wolery.
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Peer models (classmates without disabilities) who were proficient in performing a task completed one response chain each day and described the steps they performed while their classmates with disabilities observed. Three students with disabilities participated, and their performance of the response chains was assessed immediately prior to and following the peer modeling each day. A multiple probe design across response chains, replicated across children with disabilities, was used. In addition, participation and social interactions of children with disabilities and their peer models were assessed in classroom activities after daily modeling sessions. The results indicate that the peer models performed the response chains accurately and quickly, and students with disabilities acquired the response chains. Across the study, participation in classroom activities was high, social interactions were low, and neither was affected by the peer modeling intervention.
An investigation was conducted to determine the effectiveness of a constant-time-delay procedure used in combination with multiple exemplars of strangers, lures, and sites to teach a generalized response to the lures of strangers to four preschool children with disabilities. Although the correct response was quickly acquired in the training site, the response failed to generalize to the probe sites until training was conducted in vivo. Instruction in vivo resulted in acquisition, maintenance, and generalization of the response to strangers' lures. Generalization occurred across probes with novel exemplars of lures, strangers, and sites.
In this manuscript, we respond to the minimum standards for describing research subjects as proposed by the Council for Learning Disabilities (CLD) Research Committee. Three issues are raised about the standards: (a) whether justification exists for the recommended standards, (b) whether a relationship exists between the description of subjects and the probability of replication, and (c) whether all types of research require the same subject description standards. These issues are discussed, and three recommendations to investigators who use single-subject research designs are made: (1) Describe variables that control subjects' performance in baseline conditions and the contexts of that performance, (2) identify subject selection criteria, and (3) report status variables as recommended by the CLD Research Committee.
Constant time delay, a variation of progressive time delay, is a response prompting strategy designed to provide and remove prompts in a systematic manner on a time dimension. Constant time delay has two defining characteristics: (a) initial trials involve presentation of the target stimulus followed immediately by delivery of a controlling prompt; and (b) on all subsequent trials, the target stimulus is presented, a response interval of a fixed duration is delivered, the controlling prompt is provided, and a second response interval is delivered as needed. Reports of 36 studies using the constant time delay procedure with discrete behaviors were identified and analyzed. The results are described in terms of demographic variables (i.e., the types of subjects, settings, behaviors, instructors, and instructional arrangements), and the procedural parameters of the strategy. The effectiveness of the strategy and the outcome measures are summarized. Finally, the methodological adequacy of the constant time delay research is examined. Implications for practice and for further research are presented.
This research examined whether constant time delay would be effective in teaching students with moderate mental retardation in triads to perform chained tasks and whether observational learning would occur. Three chained snack preparation tasks were identified, and each student was directly taught one task. The other 2 students observed the instruction. The instructed student told the observers to watch and to turn pages of a pictorial recipe book. The teacher provided frequent praise to the instructed student based on performance and to the observers for watching the instruction and turning pages. A multiple probe design across students and tasks was used to evaluate the instruction. The results indicated that each student learned the skill he or she was taught directly, and the observers learned nearly all of the steps of the chains they observed. The implications for classroom instruction and future research in observational learning are discussed.
Teaching students with disabilities to respond appropriately to potentially dangerous situations is a useful skill that has received little research attention. This investigation taught 3 students with moderate mental retardation to remove and discard broken materials (plates, glasses) safely from (a) a sink containing dishwater, (b) a countertop, and (c) a floor. A 4th student was instructed on the sink task only. A multicomponent treatment package was used to teach the skills. Simulated materials were used initially and were replaced with broken plates and glasses. A multiple probe design was used to evaluate the effectiveness of the treatment package. The results indicated that the treatment package was effective in teaching the skills. Data were collected 1 week and 1 month following the completion of training, and indicated mixed results. No student was injured during any phase of training. Issues pertinent to teaching safety skills to students with moderate disabilities are discussed.
The effectiveness and efficiency of four response prompting conditions (progressive time delay, progressive time delay with a descriptive consequent event, system of least prompts, and system of least prompts with a descriptive consequent event) were compared. Students with moderate to severe mental retardation were taught to read functional recipe words. Maintenance and students' acquisition of incidental information were assessed when it was (a) embedded in the prompts of the system of least prompts procedure, (b) included in the descriptive praise statements following correct performance with the progressive time delay and system of least prompts procedures, and (c) not presented. A multiple probe design across behaviors, replicated across subjects, was used. Results indicated that (a) each of the procedures produced criterion level responding: (b) efficiency data on traditional measures were roughly equal; (c) maintenance checks showed no differential effects related to the instructional condition; and (d) incidental information was acquired, although it was not directly targeted for instruction.
This investigation compared the effectiveness and efficiency (sessions, errors, percent of errors, and minutes of instructional time through criterion) of constant time delay and the system of least prompts in teaching sight words to developmentally delayed preschoolers. Maintenance of sight words and generalization across instructors and materials were assessed. Also, students' acquisition of relationships between the target behavior and previously learned information were assessed. Two sessions were conducted each day in their classroom, one with each procedure. Two of the children were taught 16 words and one child learned 12 words. The parallel treatments design was used to assess the effectiveness of the two instructional strategies. The results indicated that (a) both strategies produced criterion level responding in the instructional setting, (b) constant time delay resulted in fewer total trials, errors, percent of errors, and minutes of direct instructional time through criterion than the system of least prompts, (c) both strategies produced criterion-level responding that maintained in 1-, 3- and 5-week follow-up probes, (d) both strategies resulted in generalization across instructors and materials, and (e) both strategies resulted in cross-modal generalization from expressive to receptive, receptive and expressive identification of the words' function or action, and matching the written word to a photograph of its referent.
This paper describes an investigation comparing the effectiveness and efficiency (sessions to criterion, errors to criterion, minutes of instructional time) of concurrent and isolation-intermix instruction in teaching four preschool children to read words found in community and school environments. Two students were taught words using constant time delay and two progressive time delay across the two different conditions. Concurrent instruction consisted of two sessions per day where two words were randomly presented within each session until criterion was reached and a conditional discrimination was established. The isolation-intermix condition involved two sessions per day where each word was taught in separate daily sessions until criterion was reached and a simple discrimination was established (isolation instruction); followed by random presentation of both words within each daily session until the conditional discrimination was acquired (intermix). Concurrent instruction resulted in students learning conditional discriminations in fewer trials and minutes of instructional time. These data suggest that teachers should structure their instruction to teach conditional discriminations from the beginning rather than teaching simple discriminations.
Systematic instructional strategies that investigators have used with students who display moderate to severe handicaps were identified and defined. The investigations which directly compared two or more strategies were analyzed, and summary statements/recommendations about the relative effectiveness and efficiency of the strategies were made. Analyzing the effectiveness of the procedures involved determining which strategies successfully taught skills to subjects. The efficiency of the strategies was analyzed on measures which indicated the skills were taught in a productive and timely manner (i.e., trials to criterion, sessions to criterion, errors to criterion, direct instruction time). Recommendations for future research and practice include (a) conduct more studies comparing the effectiveness and efficiency of instructional strategies, (b) conduct investigations of the specific variables of single strategies to identify the most efficient use of each procedure, (c) expand the efficiency measures to assess whether students learn information not directly targeted for instruction, and (d) conduct research to determine which strategy is best to use with given types of students and skills.
This investigation compared the effectiveness and efficiency (sessions, trials, percentage of errors, direct instructional time through criterion, and incidental information learned) of constant time delay and system of least prompts in teaching students with autism to name numerals. Two sessions were provided each day; one with constant time delay and one with system of least prompts. Two students learned 16 numerals, and one student did not learn any numerals with these two procedures. The parallel treatments design was used to assess the effects of the two instructional strategies. The results indicate that both procedures were effective in raising responding to criterion levels for two subjects. The constant time-delay procedure was more efficient than the system of least prompts procedure in terms of sessions, trials, percentage of errors, and direct instructional time through criterion. No differences in efficiency were found for the measure of incidental information learned.
The effectiveness of a 5-s constant time-delay procedure to teach three chained food preparation behaviors to four moderately retarded adolescent students was evaluated within a multiple probe design across behaviors. Results indicate that the procedure was effective in teaching all four students to make a sandwich, boil a boil-in-bag item, and bake canned biscuits. The skills maintained with at least 85% accuracy over a 3-month period. Training generalized from the school to the home setting for the 2 subjects that completed generalization probe sessions. The percentage of errors across all skills and students was less than 9%.
The effectiveness and efficiency of a progressive and constant time-delay procedure was compared. Three students with moderate mental retardation were taught to read 12 words commonly found on community signs. Six words were taught using a progressive time-delay procedure and six, using a constant time-delay procedure. The effectiveness of the two procedures was evaluated through the use of a parallel treatments design across sign words and replicated across subjects. Results show that both procedures were effective, with the constant time-delay procedure slightly more efficient in terms of number of minutes of direct instructional time and number of sessions to criterion. Both procedures generated error percentages of 1.4 or less. Findings were discussed in terms of selecting instructional strategies.
This study is a comparison of two response prompting procedures: Progressive time delay and system of least prompts. Three students with severe handicaps were each taught to identify eight functional objects, four objects with each prompting procedure. The procedures were compared in terms of effectiveness (establishing criterion level correct responding) and efficiency, (sessions and trials to criterion, errors to criterion, and the number of minutes of direct instructional time). A combination of two concurrently operating multiple probe designs (Parallel Treatments Design) in which extraneous variables were counterbalanced across sessions was employed. An analysis of the results indicates that both prompting procedures were effective in establishing correct responding at criterion levels, but the time delay procedure required fewer sessions, trials, and errors to criterion, and fewer minutes of direct instruction time than did the system of least prompts. Issues for further comparative research are discussed.
This study assessed the effects and side effects of using stereotypic behavior as a consequence for correct responding with two autistic children. The children were cued through a model to engage in stereotypic behavior contingent upon correct responses in task-training sessions. This instructional arrangement produced increases in the percent of correct responses. Measures of the stereotypic behavior used as a reinforcer, other stereotypic behaviors, and appropriate behaviors were collected during daily 5-minute free operant settings before and after the task-training sessions. No replicable, systematic changes in the percent of intervals in which subjects engaged in those side effect measures were noted. Thus, a new method for delivering stereotypic behavior as a reinforcer was investigated and produced reinforcing effects; the rate of that behavior in free operant settings was not adversely affected.
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Although single-subject research design has been discussed at some length in the recent physical therapy and occupational therapy literature, there has been little attempt to describe the procedures used for interpreting the experimental effects of such research. The purpose of this paper is to present the use of two strategies for determining whether changes have occurred as a result of experimental manipulation. The first strategy, visual analysis of graphed data, relies on visual interpretation of changes in data patterns both within and between experimental conditions. The second strategy is the use of statistical procedures such as trend estimation, the Rn statistic, and time series analysis. Finally, the issues of both clinical and statistical significance in interpreting the results of single-subject research are discussed.