After implementing the treatment for the first tier, they say, rather than reversing the just produced change, he instead applies the experimental variable to one of the other as yet unchanged responses. For example, in a study of language skills in typically developing 3-year-old children, maturation would be a particular concern. Sidman, M. (1960). Thus, for any multiple baseline design to address the threat of maturation, it must show changes in multiple tiers after substantially differing numbers of days in baseline. We can strongly argue that all tiers contact testing and session experience during baseline because we schedule and conduct these sessions. The details of situations in which this across-tier comparison is valid for ruling out threats to internal validity are more complex than they may appear. If session experience exerted a small degree of influence on the DV, an effect might be observed in settings where the behavior is more likely, but not in settings where the behavior is less likely. If this requirement is not met and a single extraneous event could explain the pattern of data in multiple tiers, then replications of the within-tier comparison do not rule out threats to internal validity as strongly. Chapter 9: Multiple Baseline And Changing Criterion Although the across-tier comparison may detect some coincidental events; it cannot be assumed to detect them all. ), Single case research methodology: Applications in special education and behavioral sciences (pp. Carr (2005) invokes this prediction, verification, and replication logic, and concludes, The nonconcurrent MB design only controls for threats associated with maturation/exposure; it does not control for historical [coincidental events] threats to internal validity, as does a concurrent MB design (p. 220). Effects of instructional set and experimenter influence on observer reliability. Throughout this article we have argued that controlling for the three main threats to internal validitymaturation, testing and session experience, and coincidental eventsin multiple baseline designs requires attention to three distinct dimensions of lag of phase changes across tiers. limitation of alternating treatment designs: o it is susceptible to multiple treatment interference, o rapid back-and-forth switching of treatments does not reflect the typical manner in which interventions are applied and may be viewed as artificial and undesirable. Any of these types of circumstances may require additional tiers in order to clearly address threats to internal validity. Cooper et al. The withdrawal phase of an A-B-A design is important because it shows that the results of the intervention weren't just a result of a difference in time. Concurrent multiple baseline designs are multiple baseline designs in which the tiers are synchronized in real time. Single-case intervention research design standards. Multiple Baseline Flashcards | Quizlet Throughout their discussion of SCD, these authors describe experimental control in terms of three processes: prediction, verification, and replication. For the purposes of this article, we define a multiple baseline design as a single-case experimental design that evaluates causal relations through the use of multiple baseline-treatment comparisons with phase changes that are offset in (1) real time (e.g., calendar date), (2) number of days in baseline, and (3) number of sessions in baseline. Shadish, W. R., Cook, T. D., & Campbell, D. T. (2002). First, the design assumes that treatment effects will be tier-specific and not spread to untreated tiers. Such events might be said to contact all tiers, but affect only one of them. With stable data, the range within which future data points will fall is These reports do not provide the information necessary to rigorously evaluate maturation or coincidental events. Coincidental events (i.e., history) are specific events that occur at a particular time (or across a particular period) and could cause changes in behavior. Exceptional Children, 71, 165179. Every multiple baseline design in which potential treatment effects are observed in some but not all tiers demonstrates that tiers are not always equally sensitive to interventions. Creating Single-Subject Research Design Graphs When he turned to multiple baseline designs, Hayes argued that AB designs are natural to clinic work and that forming a multiple baseline can consist of collecting several AB replications, which would inevitably have differing lengths of baseline (i.e., a nonconcurrent multiple baseline; p. 206). WebOften creates lots of problems BAB Reversal Design Doesnt enable assessment of effects prior to the intervention May get sequence effects May be appropriate with dangerous behaviors Addresses ethics of withholding effective treatment Need to be careful when using NCR Reversal Technique Noncontingent reversal A multiple baseline design with tiers conducted at different times during each day could show disruption due to this coincidental event in the tier assessed early in the day but not in tiers that are assessed later in the day. Perhaps a more general and powerful triad of processes that support demonstration of experimental control would be prediction, contradiction, and replication. Although the design entails two of the three elements of baseline logicprediction and replicationthe absence of concurrent baseline measures precludes the verification of [the prediction]. For example, a baseline might be The general steps for the development of the line graphs are as follows: 1. - 181.212.136.34. However, it does not rule out maturation as an alternative explanation of the change in behavior. On the other hand, across-tier comparisons may be strengthened by arranging tiers to be as similar as possible so that they would be more likely to be exposed to the same coincidental events. PubMedGoogle Scholar. It is surprising that there is no single consensus definition of multiple baseline designs. Only through repeated measurement across all tiers from the start of a study can you be confident that maturation and history threats are not influencing observed outcomes. Department of Educational Psychology, Neag School of Education, University of Connecticut, Storrs, CT, 06269, USA, You can also search for this author in Threats to Internal Validity in Multiple-Baseline Design (2020) make a somewhat different methodological criticism of nonconcurrent multiple baseline designs. If, in the initial tier, a pattern of stable baseline data is followed by a distinct change soon after the phase change, this constitutes a potential treatment effect. We have no known conflict of interest to disclose. Rand McNally. https://doi.org/10.4324/9781315150666, Chapter Single-case experimental designs: Strategies for studying behavior change. Although the claims that nonconcurrent multiple baseline designs are weaker than concurrent multiple baselines, especially with respect to threats of coincidental events, are nearly universal in the current literature, none of these authors acknowledge or address, the arguments made by Watson and Workman (1981) and Hayes (1981) in support of these designs. Multiple baseline procedure. Therefore, concurrent and nonconcurrent designs are virtually identical in control for testing and session experience. In this article, we first define multiple baseline designs, describe common threats to internal validity, and delineate the two bases for controlling these threats. PubMed They describe the control afforded by the design: The experimenter is assured that his treatment variable is effective when a change in rate appears after its application while the rate of concurrent (untreated) behaviors remains relatively constant (p. 226). For both types of comparisons, addressing maturation begins with an AB contrast in a single tier. Additional replications further reduce the plausibility of extraneous variables causing change at approximately the same time that the independent variable is applied to each tier. (p. 365), Of course, the major problem with this [nonconcurrent multiple baseline] strategy is that the control for history (i.e., the ability to assess subjects concurrently) is greatly diminished. Attachment L: Strengths and Limitations of the Single However, we can never ensure that any two contexts or any two session times are not subject to unique events during the study. Learn more about Institutional subscriptions. These views of multiple baseline designs have been carried through into much of the single-case methodological literature and textbooks to the current day. This is a preview of subscription content, access via your institution. This would align the definition with the critical features required to demonstrate experimental control and thereby allow strong causal statements based on multiple baseline designs. Without the latter you cannot conclude, with confidence, that the intervention alone is responsible for observed behavior changes since baseline (or probe) data are not concurrently collected on all tiers from the start of the investigation. Hayes, S. C. (1981). Tactics of scientific research. (Our specification of phase change offset in terms of real time, days in baseline, and sessions in baseline is unusual. Experimental and quasi-experimental designs for generalized causal inference. On the other hand, if we observe that one tier shows a change whereas other tiers that have been observed for similar amounts of time do not show similar changes, this may reduce the plausibility of the maturation threat. Pearson Education. For example, there is less room for participant-level coincidental events if all participants reside in a single group home than if they reside in different group homes in different states. They then describe the multiple baseline technique (p. 94) and two types of comparisons that contribute to its experimental control. This might be conveniently reported in the methods section or a small table in an appendix. In addition, multiple baseline designs are increasingly used in literatures that are not explicitly behavior analytic. Potential setting-level events include staffing changes in classroom, redecoration or renovation of the physical environment, and changes in the composition of the peer group in a classroom, group home, or worksite. (1975). Houghton Mifflin. 234235). What are the benefits and problems of these designs? Events that contact a single participant may be termed participant-level. Type I Errors and Power in Multiple Baseline Designs, Assessing consistency of effects when applying multilevel models to single-case data. One is that if a Watson and Workman (1981) noted that the requirement that observations be taken concurrently clearly poses problems for researchers in applied settings (e.g., schools, mental health centers), since clients with the same target behavior may only infrequently be referred at the same point in time (p. 257). On the other hand, if we see a change in a treated tier and no change in untreated tiers, does this constitute strong evidence to rule out threats to internal validity? https://doi.org/10.1007/s40614-020-00263-x, Shadish, W. R., & Sullivan, K. J. Thus, to the degree that nonconcurrent designs support longer lags between phases changes than concurrent designs, they may support stronger control of the threat of coincidental events through replicated within-tier comparisons. Ten sessions of baseline would be expected to have similar effects whether they occur in January or June. must have stable baseline and tx in first bx The replicated within-tier analysis looks to patterns of results within the other tiers. Kazdin and Kopel (1975) parallel much of Hersen and Barlows (1976) commentaryFootnote 3 but they also point out an apparent contradiction in the assumptions about behavior on which the multiple baseline design is built. In general, in a concurrent multiple baseline design across any factor, the across-tier analysis is inherently insensitive to coincidental events that are limited to a single tier of that factor. This statement, of course, fails to satisfy the operational desire for a specific number of tiers that accomplishes this function. The assumption that all tiers respond similarly to maturation may be somewhat more problematic. We are not pointing to flaws in execution of the design; we are pointing to inherent weaknesses. Hayes, S. C. (1985). https://doi.org/10.1007/s40614-022-00343-0, DOI: https://doi.org/10.1007/s40614-022-00343-0. Perspectives on Behavior Science Pearson. Second, the across-tier comparison assumes that extraneous variables will affect multiple tiers similarly. For example, physical growth and experiences with the environment can accumulate and result in relatively sudden behavioral changes when a toddler begins to walk. Control for testing and session experience requires attention to the number of sessions that participants experience. This control assumes that the replications are sufficiently offset in real time (e.g., calendar days) to ensure that a single coincidental event could not plausibly cause the effects observed in multiple tiers. The point is that although the across-tier comparison may reveal a maturation effect, there are also circumstances in which it may fail to do so. For example, phase changes in two consecutive tiers may be lagged by three sessions, but if one to three sessions are conducted per day, the baseline phases could include the same number of days (problem for controlling maturation) and the phase change could occur on the same day in both tiers (problem for controlling coincidental events). Single case experimental design and empirical clinical practice. In a concurrent multiple baseline that involves a single participant across settings, behaviors, antecedent stimuli etc., this kind of event would be expected to contact all tiers. This argument rests on the assumptions that any extraneous variable that affects one tier will (1) contact all tiers and (2) have a similar effect on all tiers. For example, for a child who is on the cusp of walking, a month of exposure to maturational variables may result in a significant improvement in walking, but much less change in fine motor skills. How many tiers do we need? Third, patterns of results influence the number of tiers needed to yield definitive conclusions. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. All three of these dimensions of lag are necessary to rigorously control for commonly recognized threats to internal validity and establish experimental control. A given period of maturation may affect various participants, various behaviors, or behaviors in various settings in different ways. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. Google Scholar, Gast, D. L., Lloyd, B. P., & Ledford, J. R. (2018). It is clear that we cannot claim that these assumptions are always valid for multiple baseline designs. However, the specific issues in this controversy have never been thoroughly identified, discussed, and resolved; and instead a consensus emerged without the issues being explicitly addressed. . If the pattern of change shortly after implementation of the treatment is replicated in the other tiers after differing lengths of time in baseline (i.e., different amounts of maturation), maturation becomes increasingly implausible as an alternative explanation. Applied behavior analysis (3rd ed.). If we observe a potential treatment effect in one tier and corresponding changes in untreated tiers after similar amounts of time (i.e., number of days), maturation becomes a more plausible alternative explanation of the initial potential treatment effect. In the case of multiple baseline designs, a stable baseline supports a strong prediction that the data path would continue on the same trajectory in the absence of an effective treatment; these predictions are said to be verified by observing no change in trajectories of data in other tiers that are not subjected to treatment; and replication is demonstrated when a treatment effect is seen in multiple tiers. As we argued above, the observation of no change in an untreated tier is not strong evidence against a coincidental event affecting the treated tier. If an effective treatment were to have a broad impact on multiple tiers, the logic of the design would be to falsely attribute these effects to possible extraneous variables. Nonconcurrent multiple baseline designs and the evaluation of educational systems. However, as Hayes (1985) pointed out, even with the most rigorous care in experimental design, we can never give two individuals the same experiences outside of our experimental sessions. Consequently, it is often difficult or impossible to dismiss rival hypotheses or explanations. If a nonconcurrent multiple baseline has a long lag in real time between phase changes (e.g., weeks or months), this may provide stronger control than a design with a lag of one or several days. Single-case research designs: Methods for clinical and applied settings (3rd ed.). Based on the logic laid out in this article, we believe that the treats of maturation and testing and session experience are controlled equivalently in concurrent and nonconcurrent design. These observations lead us to the conclusion that neither of the critical assumptions that coincidental events will (1) contact and (2) have similar impact on all tiers can be assumed to be valid. Throughout this article we have referred to the importance of replicating within-tier comparisons, emphasizing the idea that tiers must be arranged with sufficient lag in phase changes so that specific threats to internal validity are logically ruled out. Any one tier may, at best, demonstrate a potential treatment effect; however, a set of three or more tiers may strongly address the threat of coincidental events and clearly demonstrate experimental control.

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