Poor execution can certainly worsen these problems, but good execution cannot eliminate them. The bottom line is that the experimenter can never know whether a coincidental event has contacted only a single tier of a concurrent multiple baseline and, therefore, whether it is possible for the across-tier comparison to detect this threat. Having identified the criticisms of nonconcurrent multiple baseline designs, we now turn to a detailed analysis of threats to internal validity and features that can control these threats. Cooper, J. O., Heron, T. E., & Heward, W. L. (2020). . Advantages and Disadvantages of ABA Design. Although the across-tier comparison may detect some coincidental events; it cannot be assumed to detect them all. (1975). Single-case research designs: Methods for clinical and applied settings (3rd ed.). In this design, behavior is measured across either multiple individuals, behaviors, or settings. Webmultiple baseline (3 forms) 1. across bx 2. across settings, 3. across subjects or groups using 3-5 tiers. The consensus in recent textbooks and methodological papers is that nonconcurrent designs are less rigorous than concurrent designs because of their presumed limited ability to address the threat of coincidental events (i.e., history). Describe the retrospective and prospective research designs. Kazdin, A. E. (2021). An important question for researchers, reviewers, and readers of research is whether the amount of lag is sufficient for a specific study. Kazdin, A. E. (2021). WebMultiple Baseline Description Multiple measures are used to obtain data over two or more baselines The end result appears visually as a series of A-B designs on top of one another The DV may consist of 2 or more different behaviors Versatile and relatively easy to understand Perhaps the most common design in use today Multiple Baseline Design If For example, in a multiple baseline across settings, the settings could present somewhat different demands. 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. Shadish, W. R., Cook, T. D., & Campbell, D. T. (2002). The across-tier analysis of coincidental events is the main way that concurrent and nonconcurrent multiple baselines differ. Hersen and Barlows (1976) textbook appears to be the first complete description of the multiple baseline design with many of the ideas about experimental control that are current to this day. Timothy A. Slocum, P. Raymond Joslyn, Sarah E. Pinkelman, Thomas R. Kratochwill, Joel R. Levin, Esther R. Lindstrm, Marc J. Lanovaz, Stphanie Turgeon, Tara L. Wheatley, Jonathan Rush, Philippe Rast & Scott M. Hofer, Perspectives on Behavior Science Adding multiple tiers to the design allows for two types of additional comparisons to be used to evaluate, and perhaps rule out, these threats: (1) replications of baseline-treatment comparisons within subsequent tiers (i.e., horizontal analysis), and (2) comparisons across tiers (i.e., vertical analysis). 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. Correspondence to This is consistent with the judgements made by numerous existing standards and recommendations (e.g., Gast et al., 2018; Horner et al., 2005; Kazdin, 2021; Kratochwill et al., 2013). Testing and session exposure may be particularly troublesome in a study that requires taking the participant to an unusual location and exposing them to unusual assessment situations in order to obtain baseline data. Maturational changes may be smooth and gradual, or they may be sudden and uneven. How many tiers do we need? Behavior Therapy, 6(5), 601608. WebDisadvantages to Multiple Baseline Designs -Weaker method of showing experimental control than a reversal (b/c no withdrawal of treatment) -Delay in treatment can occur as To offer some guidance, we believe that under ideal conditionsadequate lags between phase changes, circumstances that do not suggest that threats are particularly likely, and clear results across tiersthree tiers in a multiple baseline can provide strong control against threats to internal validity. For example, physical growth and experiences with the environment can accumulate and result in relatively sudden behavioral changes when a toddler begins to walk. In such an instance, there may be a disruption to experimental control in only one-tier of the design and not others, thus influencing the degree of internal Later they present an overall evaluation of the strength of multiple baseline designs, attributing its primary weakness to its reliance on the across-tier comparison, The multiple baseline design is considerably weaker than the withdrawal design as the controlling effects of the treatment on each of the target behaviors is not directly demonstrated . Thus, the assumption that the coincidental event contacts all tiers would be valid and the across-tier analysis might reveal the effects of this sort of event. The issue of concurrence of tiers should be considered along with many other design variations that can be manipulated to create a design that fits the particular experimental challenges of a particular study. When changes in data occur immediately after the phase change, are large in magnitude, and are consistent across tiers, threats to internal validity tend to be less plausible explanations of the data patterns, and fewer tiers would be required to rule them out. They do not mention the across-tier comparison, presumably because they believe that this analysis is not necessary to establish experimental control. These events would contact all tiers of a MB that take place in that single setting, but not tiers in other settings. An example of multiple baseline across behaviors might be to use feedback to develop a comprehensive exercise program that involves stretching, aerobic exercise, The time lag must be sufficiently long so that no single event could produce potential treatment effects in more than one tier. Experimental and quasi-experimental designs for research. The multiple baseline design is useful for interventions that are irreversible due to learning effects, and when treatment cant be withdrawn. https://doi.org/10.1177/0145445516644699, Department of Special Education & Rehabilitation Counseling, Utah State University, 2865 Old Main Hill, Logan, UT, 84322, USA, Timothy A. Slocum,Sarah E. Pinkelman,P. Raymond Joslyn&Beverly Nichols, You can also search for this author in An important drawback of pre-experimental designs is that they are subject to numerous threats to their validity. Book Therefore, we view this approach as less desirable than the standard multiple baseline design across subjects and suggest that it should be employed only when the standard approach is not feasible. For both types of comparisons, addressing maturation begins with an AB contrast in a single tier. Multiple baseline designs can rigorously control these threats to internal validity. https://doi.org/10.1177/001440290507100203, Johnston, J. M., Pennypacker, H. S., & Green, G. (2020). Application of multiple baseline designs in behavior analytic research: Evidence for the influence of new guidelines. Thus, both of the articles introducing nonconcurrent multiple baselines made explicit arguments that replicated within-tier comparisons are sufficient to address the threat of coincidental events. Journal of Consulting & Clinical Psychology, 49(2), 193211. (pp. As Kazdin and Kopel point out, it is clearly possible for treatments to have broad effects on multiple tiers and for extraneous variables to have narrow effects on a specific tier. PubMed Central Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Smith (2012) found that SCD was reported in 143 different journals that span a variety of fields such as behavior analysis, psychology, education, speech, and pain management; across these fields, multiple baselines account for 69% of SCDs. 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. WebIdentify the limitations of multiple baseline design 1.Does not demonstrate experimental control directly 2Provides more information about effectiveness of treatment Single-case experimental designs: A systematic review of published research and current standards. WebDisadvantage: Covariance among subjects may emerge if individuals learn vicariously through the experiences of other subjects Also, identifying multiple subjects in the same Examples could include family events, illness, changed social interactions (e.g., breaking up with a partner), losing or gaining access to a social service program, etc. It is surprising that there is no single consensus definition of multiple baseline designs. Still, for a given study, the results influence the number to tiers required in a rigorous multiple baseline design. One is that if a A researcher who puts great confidence in the across-tier comparison could falsely reject the idea that coincidental events were the cause of observed effects. Characteristics of single-case designs used to assess intervention effects in 2008. In order to demonstrate experimental control, the researcher makes two paradoxical assumptions. In addition, multiple baseline designs are increasingly used in literatures that are not explicitly behavior analytic. The reversal model is fine for many questions, but in some instances, removing a type of treatment could be unwise or even unethical. WebMULTIPLE BASELINE DESIGN Most widely used for evaluating treatment effects in ABA Highly flexible Do not have to withdraw treatment variable Is an alternative to reversal Google Scholar. Nonconcurrent multiple baseline designs and the evaluation of educational systems. WebA multiple baseline design across behaviors was used to examine intervention effects. Strategies and tactics of behavioral research and practice (4th ed.). We can strongly argue that all tiers contact testing and session experience during baseline because we schedule and conduct these sessions. Cooper et al. Reasons for these specifications will become clear later in the article.) However, an across-tier comparison is not definitive because testing or session experience could affect the tiers differently. Rather, the passage of time allows for more opportunities for participants to interact with their environmentleading to maturational changes. 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 Timothy A. Slocum. Single case experimental designs: Strategies for studying behavior change (3rd ed.). This statement, of course, fails to satisfy the operational desire for a specific number of tiers that accomplishes this function. Further, if the potential treatment effect is more gradual (as one might expect from an educational intervention on a complex skill), maturational changes may be impossible to distinguish from treatment effects. That is, it is not strong evidence verifying the prediction of no change in the initial tier in the absence of an intervention. The problem of tier-specific coincidental events can be reduced by selecting tiers that differ on only a single factor (e.g., participants, settings, behaviors) and are as similar as possible on that factor. 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]. This might be conveniently reported in the methods section or a small table in an appendix. Features of the target behaviors, participants, measurement, and so forth can make threats to internal validity more or less likely. However, in a concurrent multiple baseline across participants, participant-level events contact only a single tier (participant)the coincidental event would not contact other tiers (participants)we might say that the across-tier analysis is inherently insensitive to detecting this kind of event. Watson and Workman described a nonconcurrent multiple baseline design in which participants could be begin a study as they became known to the researcher. (2018) state: Confidence that maturation and history [coincidental events] threats are under control is based on observing (a) an immediate change in the dependent variable upon introduction of the independent variable, and (b) baseline (or probe) condition levels remaining stable while other tiers are exposed to the intervention. 7. 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. Third, we explore how concurrent and nonconcurrent multiple baselines address each of the main threats to internal validity. However, researchers in clinical, educational, and other applied settings recognized that they could expand research much further if the tiers of a multiple baseline could be conducted as they became available sequentially rather than simultaneously. This has been the sharpest point of criticism of nonconcurrent multiple baselines. 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 this patterna clear prediction from baseline being contradicted when and only when the independent variable is introducedcan be replicated across additional tiers of the multiple baseline, then the evidence of a treatment effect is incrementally strengthened. Part of Springer Nature. Pearson Education. It is interesting that this emphasis on across-tier comparisons is the opposite of that evident in Baer et al. Routledge/Taylor & Francis Group. WebIn yet a third version of the multiple-baseline design, multiple baselines are established for the same participant but in different settings. AB Design. Create the data table in Sheets; 2. To answer the first question, the one must distinguish signal (systematic change) from noise (unsystematic variance). The non-concurrent multiple baseline across-individuals design: An extension of the traditional multiple baseline design. In this article, we first define multiple baseline designs, describe common threats to internal validity, and delineate the two bases for controlling these threats. Therefore, concurrent and nonconcurrent designs are virtually identical in control for testing and session experience. This consensus is that nonconcurrent multiple baseline designs are substantially weaker than concurrent designs (e.g., Cooper et al., 2020; Johnston et al., 2020; Kazdin, 2021). 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. 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. Pearson. 234235). 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). This comparison may reveal a likely maturation effect. This controversy began soon after the first formal description of nonconcurrent multiple baseline designs by Hayes (1981) and Watson and Workman (1981). https://doi.org/10.1007/s40614-022-00343-0, SI: Commentary on Slocum et al, Threats to Internal Validity. WebMultiple-Baseline Designs There are two potential problems with the reversal designboth of which have to do with the removal of the treatment. The across-tier comparison is an additional basis for evaluating alternative explanations. Therefore, researchers must exercise extreme caution in interpreting and generalizing the results from pre-experimental studies. The purposes of this article are to (1) thoroughly examine the impact that threats to internal validity can have on concurrent and nonconcurrent multiple baseline designs; (2) describe the critical features of each design type that control for threats to internal validity; and (3) offer recommendations for use and reporting of concurrent and nonconcurrent multiple baseline designs. The within-tier comparison may be further strengthened by increasing independence of the tier in other dimensions. 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). A baseline (A) and an intervention (B) are included in a straightforward AB design psychological experiment (B). First, the design assumes that treatment effects will be tier-specific and not spread to untreated tiers. (1981). Likewise, in a multiple baseline across settings, selecting settings that tend to share extraneous events would make the across-tier analysis more powerful than would selecting settings that share few common events. Part of Springer Nature. However, current practice provides little or no direct information on either the temporal duration (e.g., number of days) of baseline nor the offset between phase changes in real time (i.e., number of calendar days between phase changes). For example, knowing the date of session 10 in tier 1 tells us nothing about the date of session 10 in tier 2. Thus, although the across-tier analysis does provide a test of the maturation threat, a lack of change in untreated tiers cannot definitively rule it out. The Nonconcurrent Multiple-Baseline Design: It is What it is and Not Something Else. Recognizing these three dimensions of lag has implications for reporting multiple baseline designs. Controlling for maturation requires baseline phases of distinctly different temporal durations (i.e., number of days); controlling for testing and session experience requires baseline phases of substantially different number of sessions; and controlling for coincidental events requires phase changes on sufficiently offset calendar dates. . Thus, the additional temporal separation that is possible in a nonconcurrent design is a strength rather than a weakness in controlling for coincidental events. PubMed When determining whether a multiple baseline study demonstrates experimental control, researchers examine the data within and across tiers and also consider the extent to which alternative explanations (e.g., extraneous variables or confounds) could plausibly account for the obtained data patterns. Some current dimensions of applied behavior analysis. Second, in a remarkably understated reference to the across-tier comparison, Baer et al. Google Scholar. Webtreatment (Kazdin & Nock, 2003). For example, two rooms in the same treatment center would share more coincidental events than a room in a treatment center and another room at home. 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. and (2) Was any change the result of the independent variable? This raises the question of how many replications are necessary to establish internal validity. Neither the within-tier comparison, nor the across-tier comparison depends on the tiers being conducted simultaneously; both types of comparisons only require that phase changes occur after substantially different amounts of time since the beginning of baselinethat is, each tier is exposed to different amounts of maturation (i.e., days) prior to the phase change. The across-tier analysis can provide an additional set of comparisons that may reveal a maturation effect, but it is not a conclusive test. The lag between phase changes must be long enough that maturation over any single amount of time cannot explain the results in multiple tiers. (1973). (p. 206). Testing and session experience encompasses features of experimental sessions (both baseline and intervention phases) other than the independent variable that could cause changes in behavior. Campbell, D. T., & Stanley, J. C. (1963). Perspect Behav Sci 45, 619638 (2022). Create the graph from the data in Sheets; 3. Some researchers believe ABAB is a stronger design since it has multiple reversals. 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). There is ample empirical evidence of differential impact of variables across tiers. Nonconcurrent multiple baseline designs are those in which tiers are not synchronized in real time. Harvey, M. T., May, M. E., & Kennedy, C. H. (2004). 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. 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. Slocum, T.A., Pinkelman, S.E., Joslyn, P.R. These views of multiple baseline designs have been carried through into much of the single-case methodological literature and textbooks to the current day. . 2023 Springer Nature Switzerland AG. So, for example, session 10 in tier 2 must take place at some time between tier 1s session 9 and 11. In the past, there was significant controversy regarding the relative rigor of concurrent and nonconcurrent 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. 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. The replicated within-tier analysis looks to patterns of results within the other tiers. If an extraneous variable were to have a tier-specific effect, it would be falsely interpreted as a treatment effect. PubMed Other design features that contribute to the isolation of tiers such that any single extraneous variable is unlikely to contact multiple tiers can also strengthen the independence of tiers. Addressing the second question requires data analysis that is informed by the specifics of the study. These reports do not provide the information necessary to rigorously evaluate maturation or coincidental events. Basic Books. 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. 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. Use of brief experimental analyses in outpatient clinic and home settings. Second, we briefly summarize historical methodological writing and current textbook treatment of these designs. In both forms of multiple baseline designs, a potential treatment effect in the first tier would be vulnerable to the threat that the changes in data could be a result of testing or session experience. Single case experimental design and empirical clinical practice. This pattern seriously weakens the argument that the independent variable was responsible for the change in the treated tier. Under these conditions, the experimental rigor of concurrent multiple baselines is identical to nonconcurrent multiple baselines; coincidental events that contact a single tier cannot be detected by an across-tier analysis. In both within- and across-tier comparisons, the dates on which the sessions took place are not relevant to the effects of testing and session experience. Two articles published in 1981 described and advocated the use of nonconcurrent multiple baseline designs (Hayes, 1981; Watson & Workman, 1981). In the end, judgments about the plausibility of threats and number of tiers needed must be made by researchers, editors, and critical readers of research. The nature of control for coincidental events (i.e., history) provided by the within-tier comparison in both concurrent and nonconcurrent multiple baseline designs is relatively straightforward. Barlow, D. H., Nock, M. K., & Hersen, M. (2009). Single-case research designs: Methods for clinical and applied settings (3rd ed.). They state, the nonconcurrent multiple baseline across participants design is inherently weaker than other multiple baseline design variations. Journal of Applied Behavior Analysis, 30(3), 533544. 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. Natural multiple baselines across persons: A reply to Harris and Jenson. . By synchronized we mean that session 1 in all tiers takes place before session 2 in any tier, and this ordinal invariance of session number across tiers is true for all sessions. 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. To summarize, the replicated within-tier analysis with sufficient lag can rigorously control for the threat of maturation. However, it does not rule out maturation as an alternative explanation of the change in behavior. Independent from Watson and Workman (1981), Hayes (1981) published a lengthy article introducing SCDs to clinical psychologists and made the point that these designs are well-suited to conducting research in clinical practice. It is possible that a coincidental event may be present for all tiers but have different effects on different tiers. For example, in a study of language skills in typically developing 3-year-old children, maturation would be a particular concern. 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. We have no known conflict of interest to disclose. 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. 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. Under the proposed definition, such a study would not be considered a full-fledged multiple baseline. Data from the treatment phase in one tier can be compared to corresponding baseline data in another tier.
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