They never raise the question of whether replicated within-tier comparisons are sufficient to rule out threats to internal validity and establish experimental control. Rand McNally. Perspectives on Behavior Science, 43, 605616. B. Cooper et al. While the fact that the researcher does not use a large number of participants has its advantages, it also has a downside: Because the experimental trials are run on only one subject, it is difficult to empirically show with the experiment's data that the findings will generalize out to larger populations. However, we can never ensure that any two contexts or any two session times are not subject to unique events during the study. Perhaps a more general and powerful triad of processes that support demonstration of experimental control would be prediction, contradiction, and replication. 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 Rather, the passage of time allows for more opportunities for participants to interact with their environmentleading to maturational changes. To summarize, the replicated within-tier analysis with sufficient lag can rigorously control for the threat of maturation. Department of Educational Psychology, Neag School of Education, University of Connecticut, Storrs, CT, 06269, USA, You can also search for this author in The current SCD methodological literature and most SCD textbooks claim that because the tiers of nonconcurrent multiple baseline are not synchronized in real time they have a diminished capacity to control for extraneous variables, in particular coincidental events (e.g., Carr, 2005; Gast et al., 2018; Harvey et al., 2004; Johnston et al., 2020). Coincidental events include divorce, changing of living situation, changes in school or work schedule, physical injury, changes in a setting such as construction, changes in coworkers or staffing, and many others. Each of these three types of threats point us to distinct dimensions of the lag between phase changes that must be controlled for in order to achieve experimental control: for maturation, we control for elapsed time (e.g., days); for testing and session experience, we must be concerned with the number of sessions; and for coincidental events, we must be concerned with the specific time periods (i.e., calendar dates) of the study. The present article is focused on the second questionwhether systematic changes in data can be attributed to the treatment. In this highly influential early textbook on SCD, Hersen and Barlow describe only the across-tier analysis and fail to mention replicated within-tier comparisons. Oxford University Press. Such events might be said to contact all tiers, but affect only one of them. Nonconcurrent multiple baseline designs for educational program evaluation. 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. Although it is plausible that an extraneous variables influence could coincide with one phase change, it is less plausible that such a coincidence would occur twice, and even less plausible that it would occur three times. because a non-concurrent design does not allow any AB comparisons across baselines, it omits the opportunity to see if responding under the control condition changes when the treatment condition is implemented in the other baseline. 288335). 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. Correspondence to Routledge. The concurrent multiple baseline design opened up many new opportunities to conduct applied research in contexts that were not amenable to other SCDs. Experimental and quasi-experimental designs for generalized causal inference. One is that if a This comparison can reveal the influence of an extraneous variable only if it causes a change in several tiers at about the same time. The logic of replicated within-tier analysis applies equally to concurrent and nonconcurrent designs. 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). Events that contact a single participant may be termed participant-level. For example, in a study of language skills in typically developing 3-year-old children, maturation would be a particular concern. It is interesting that this emphasis on across-tier comparisons is the opposite of that evident in Baer et al. One area that has, in the past, been particularly controversial is the experimental rigor of concurrent versus nonconcurrent multiple baseline designs; that is, the degree to which each can rule out threats to internal validity. Using Single-Case Designs in Practical Settings: Is Within-Subject Replication Always Necessary? It is possible that a coincidental event may be present for all tiers but have different effects on different tiers. Craig H. Kennedy. WebIn yet a third version of the multiple-baseline design, multiple baselines are established for the same participant but in different settings. So, for example, session 10 in tier 2 must take place at some time between tier 1s session 9 and 11. 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. This understanding of the primary role of replicated within-tier comparisons also implies that, when there is a trade-off, design options that improve control through the within-tier comparisons should take precedence over those that would improve control through across-tier comparisons. Further, for the across-tier comparison to detect the influence of a coincidental event, that event must not only contact multiple tiers, it must cause similar changes in the dependent measure across multiple tiers. 7. Harvey, M. T., May, M. E., & Kennedy, C. H. (2004). In addition, multiple baseline designs are increasingly used in literatures that are not explicitly behavior analytic. Behavioral Interventions, 20(3), 219224. Single case experimental designs: Strategies for studying behavior change (3rd ed.). Web14 : A multiple-baseline design requires that the targeted behavior return to baseline levels when the treatment is removed. 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. Child Development, 44, 547554. 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. Some current dimensions of applied behavior analysis. (1968) who emphasized the replicated within-tier comparison. They then describe the multiple baseline technique (p. 94) and two types of comparisons that contribute to its experimental control. WebGive two advantages and two disadvantages of quasi-experimental designs. (Our specification of phase change offset in terms of real time, days in baseline, and sessions in baseline is unusual. Second, as we have discussed above, the amount of lag between phase changes (in terms of sessions in baseline, days in baseline, and elapsed days) is the primary design feature that reduces the plausibility of any single threat accounting for changes in multiple tiers, and thereby threatening the internal validity of the design as a whole. Nonconcurrent multiple baseline designs, however, do not afford this comparison. Johnston, J. M., Pennypacker, H. S., & Green, G. (2010). 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. The within-tier comparison may be further strengthened by increasing independence of the tier in other dimensions. If A changes after B is put into practice, a researcher can draw the Conclusion that B caused A to change. (2011). (1975). With stable data, the range within which future data points will fall is 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. 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. A functional relation can be inferred if the pattern of data demonstrates experimental controlthe experimenters ability to produce a change in the dependent variable in a precise and reliable fashion (Sidman, 1960). Sidman, M. (1960). 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. We have no known conflict of interest to disclose. Threats to Internal Validity in Multiple-Baseline Design Variations, https://doi.org/10.1007/s40614-022-00326-1, Concurrence on Nonconcurrence in Multiple-Baseline Designs: A Commentary on Slocum et al. As a result, concurrent and nonconcurrent designs are virtually identical in their control for maturation threats. We can strongly argue that all tiers contact testing and session experience during baseline because we schedule and conduct these sessions. A : true B : false. Journal of Consulting & Clinical Psychology, 49(2), 193211. 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. That is, experimental control has not been convincingly demonstrated. Houghton Mifflin. That is, session numbers do not necessarily correspond to the same periods of real time across tiers. Perspect Behav Sci 45, 647650 (2022). 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. WebAB design advantages - -simple to use AB design disadvantages - -cannot be used to make a confident assumption of a functional relation -vulnerable to confounding variables -does not provide for replication AB design - basic single subject design AB design has two phases of design - A: Baseline B: Intervention Reversal Design referred to as - The definition states that there must be sufficient lag between phase changesthis is not further specified because the amount of lag necessary to ensure that any single amount of maturation, number of sessions, or coincidental event could not cause changes in multiple tiers must be determined in the context of the particular study. Therefore, we believe that these features should be explicitly included in the definition of multiple baseline designs. Textbook authors, editors, and readers of research should consider nonconcurrent multiple baseline designs to be capable of supporting conclusions every bit as strong as those from concurrent designs. This would draw attention to the relationship between the prediction from baseline and the (possible) contradiction of that prediction by the obtained treatment-phase data, and the replication of this prediction-contradiction pair in subsequent tiers. 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. Campbell, D. T., & Stanley, J. C. (1963). 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. 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 Taplin, P. S., & Reid, J. Rosales-Ruiz, J., & Baer, D. M. (1997). First, studies differ with respect to the experimental challenges imposed by the phenomena under study. . Effects of instructional set and experimenter influence on observer reliability. 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. 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. We will focus on the three types of threats that are addressed through comparisons between baseline and treatment phases in multiple baseline designs: maturation, testing and session experience, and coincidental events.Footnote 1. Threats to Internal Validity in Multiple-Baseline Design Variations. A potential treatment effect in any single tier could plausibly be explained as a result of a coincidental event. They do not elaborate on the importance of this type of comparison. For example, physical growth and experiences with the environment can accumulate and result in relatively sudden behavioral changes when a toddler begins to walk. We use the term potential treatment effect to emphasize that the evidence provided by this single AB within-tier comparison is not sufficient to draw a strong causal conclusion because many threats to internal validity may be plausible alternative explanations for the data patterns. Kazdin, A. E., & Kopel, S. A. 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. 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. WebWeaknesses of multiple baseline designs: There are certain functional relations that may not be clearly understood by this design This design is time consuming and The multiple baseline design is useful for interventions that are irreversible due to learning effects, and when treatment cant be withdrawn. These events would contact all tiers of a MB that take place in that single setting, but not tiers in other settings. These views of multiple baseline designs have been carried through into much of the single-case methodological literature and textbooks to the current day. PubMed 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 example, in a multiple baseline across participants, all the residents of a group home may contact peanut butter and jelly sandwiches for lunch but this change may disrupt the behavior of residents with a mild peanut allergy, but not other residents. This controversy began soon after the first formal description of nonconcurrent multiple baseline designs by Hayes (1981) and Watson and Workman (1981). 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. Controlling for coincidental events requires attention to the specific dates on which events occur. The use of single-subject research to identify evidence-based practice in special education. 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). Predi Abab Design Essay https://doi.org/10.3758/s13428-011-0111-y, Article 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. 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. 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. Textbooks commonly describe and characterize the design without clearly defining it. Behavioral Interventions, 33(2), 160172. Application of multiple baseline designs in behavior analytic research: Evidence for the influence of new guidelines. 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. Nonconcurrent multiple baseline designs and the evaluation of educational systems. The ABA or Reversal Design We will explore these issues extensively after we sketch the historical development of multiple baseline designs and criticisms of nonconcurrent multiple baselines. Reasons for these specifications will become clear later in the article.) The lack of change in untreated tiers should be interpreted only as weak evidence supporting internal validity given the plausible alternative explanations of this lack of change. Two articles published in 1981 described and advocated the use of nonconcurrent multiple baseline designs (Hayes, 1981; Watson & Workman, 1981). This question cannot be addressed by data analysis alone; any pattern of data, no matter how dramatic, could be a result of an extraneous variable if the experimental design features are not properly arranged. Other threats to internal validity such as (1) ambiguous temporal precedence, (2) selection, (3) regression, (4) attrition, and (5) instrumentation are addressed primarily through other design features. Elapsed time does not directly cause maturational changes in behavior. 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. In this case, the across-tier comparison would give the false appearance of strong internal validity. Horner, R. H., Carr, E. G., Halle, J., McGee, G., Odom, S., & Wolery, M. (2005). The across-tier comparison of concurrent multiple baseline designs is less certain and definitive than it may appear. 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. In J. R. Ledford & D. L. Gast (Eds. 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. WebLike RCTs, the multiple baseline design can demonstrate that a change in behavior has occurred, the change is a result of the intervention, and the change is significant. Concurrent and nonconcurrent multiple baseline designs address maturation in virtually identical ways through both within- and across-tier comparisons. Finally, we make recommendations for more rigorous use, reporting, and evaluation of multiple baseline designs. https://doi.org/10.1002/bin.191, Article This might be conveniently reported in the methods section or a small table in an appendix. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Multiple baseline designsboth concurrent and nonconcurrentare the predominant experimental design in modern applied behavior analytic research and are increasingly employed in other disciplines. Research methodologists have identified numerous potential alternative explanations that are threats to internal validity (e.g., Campbell & Stanley, 1963; Cooper et al., 2020; Kazdin, 2021; Shadish et al., 2002). (1973). In this case, the effects of this kind of event could be revealed through the across-tier comparison of participants or behaviors that have not been exposed to the independent variable. 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). Both concurrent and nonconcurrent multiple baseline designs also afford the same across-tier comparison; both can show a potentialtreatment effect after a certain number of baseline sessions in one tier and a lack of effect after that same number of sessions in another tier. We can identify at least three general categories of issues that influence the number of tiers required to render threats implausible: challenges associated with the phenomena under study, experimental design features, and data analysis issues. However, if this within-tier pattern is replicated in multiple tiers after differing numbers of baseline sessions, this threat becomes increasingly implausible. the effects of the treatment variable are inferred from the untreated behaviors (p. 227). Estimating reliabilities and correcting for sampling error in indices of within-person dynamics derived from intensive longitudinal data, Optimizing Detection of True Within-Person Effects for Intensive Measurement Designs: A Comparison of Multilevel SEM and Unit-Weighted Scale Scores, https://doi.org/10.1023/B:JOBE.0000044735.51022.5d, https://doi.org/10.1037/0022-006X.49.2.193, https://doi.org/10.1177/001440290507100203, https://doi.org/10.1016/S0005-7894(75)80181-X, https://doi.org/10.1007/s40614-020-00263-x, https://doi.org/10.3758/s13428-011-0111-y, https://doi.org/10.1016/0005-7916(81)90055-0, http://creativecommons.org/licenses/by/4.0/, SI: Commentary on Slocum et al, Threats to Internal Validity. 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. 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. In this article, we argue that the primary reliance on across-tier comparisons and the resulting deprecation of nonconcurrent designs are not well-justified. https://doi.org/10.1901/jaba.1968.1-91, Article 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. 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. Watson and Workman did not explicitly address threats to internal validity other than coincidental events. WebA multiple baseline design across behaviors was used to examine intervention effects. Strategies and tactics of behavioral research and practice (4th ed.). Thus, a multiple baseline with phase changes sufficiently lagged (in terms of number of sessions) provides rigorous control for this threat. Coincidental events share the characteristic that their behavioral impact is expected to be a function of particular dates. WebDisadvantage: Covariance among subjects may emerge if individuals learn vicariously through the experiences of other subjects Also, identifying multiple subjects in the same This raises the question of how many replications are necessary to establish internal validity. Journal of Behavioral Education, 13, 267276. Concurrence is not necessary to detect and control for maturation. 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 These variables share the key characteristic that their impact would be expected to accumulate as a function of number of experimental sessions. Experimental and quasi-experimental designs for research. 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. Peer reviewers and editors who serve as gatekeepers for the scientific literature must also have a deep understanding of these issues so that they can distinguish between stronger and weaker research, ensure that information critical to evaluating internal validity is included in research reports, and assess the appropriateness of discussion and interpretation of results. In a review of the SCD literature, Shadish and Sullivan (2011) found multiple baseline designs making up 79% of the SCD literature (54% multiple baseline alone, 25% mixed/combined designs). An important drawback of pre-experimental designs is that they are subject to numerous threats to their validity. Pearson Education. In this section, we examine how within- and across-tier comparisons may support (or fail to support), internal validity in concurrent and nonconcurrent multiple baseline designs. However, an across-tier comparison is not definitive because testing or session experience could affect the tiers differently. An important question for researchers, reviewers, and readers of research is whether the amount of lag is sufficient for a specific study. The general steps for the development of the line graphs are as follows: 1. Thus, the additional temporal separation that is possible in a nonconcurrent design is a strength rather than a weakness in controlling for coincidental events. WebAnother limitation cited for single-subject designs is related to testing. . The dimension of time is recognized in the requirement that phase changes be lagged in real timethat is, the date on which the phase changes are made. Behavior Therapy, 6(5), 601608. First, in the replicated within-tier comparison, each tier of the design is exposed to the treatment at a different point in time. Because experimental circumstances and design elements vary so greatly, no universal answer can be given. In order to demonstrate experimental control, the researcher makes two paradoxical assumptions. Multiple baseline and multiple probe designs. This comparison may reveal a likely maturation effect. If either of these assumptions are not valid for a coincidental event, then the presence and function of that event would not be revealed by the across-tier analysis. Part of Springer Nature. Throughout their discussion of SCD, these authors describe experimental control in terms of three processes: prediction, verification, and replication. 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. Slocum, T.A., Pinkelman, S.E., Joslyn, P.R. Pearson. 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. On resolving ambiguities of the multiple-baseline design: Problems and recommendations. These baseline-treatment comparisons, which we will refer to as tiers, differ from one another with respect to participants, behaviors, settings, stimulus materials, and/or other variables.

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