Academic journal article The Psychological Record

Comparison of Probe Procedures in the Assessment of Chained Tasks

Academic journal article The Psychological Record

Comparison of Probe Procedures in the Assessment of Chained Tasks

Article excerpt

The fields of special education and behavioral science have devoted considerable attention to identifying evidence-based practices (EBPs) for individuals with disabilities (Cook & Odom, 2013; Slocum et al., 2014). Many of these practices have been empirically evaluated using single-case designs (SCDs). This is not surprising given the benefits and historical precedent of using SCD with individuals with disabilities when evaluating behavioral interventions (Baer, Wolf, & Risley, 1968; Homer et al., 2005). In order to validate practices as evidence based, the methods used should minimize possible threats to internal validity. For example, testing threats may occur when repeated measurement alone results in therapeutic or contratherapeutic changes in the value of the dependent variable (Gast, 2014). Uncontrolled facilitative effects can result in the dependent variable improving in baseline, thus confounding interpretations of the intervention effects. The occurrence of an improving baseline may prevent or delay the participant from receiving intervention (Johnston & Pennypacker, 2009). Inhibitive testing effects can also occur, resulting in suppressed responding and a more immediate introduction of intervention than would otherwise occur. In this scenario, visual analysis can produce attribution of overestimated levels of effect to the independent variable. Unfortunately, assessment of testing threats in baseline is difficult, given the likelihood of publication bias in the case of facilitative effects (e.g., these effects may result in no identification of a functional relation or a smaller effect, leading to less compelling findings and lower likelihood of publication; Shadish, Zelinsky, Vevea, & Kratochwill, 2016) and the inability to differentiate inhibitive effects from true effects (e.g., a baseline consisting of 0% correct responding may reflect true unknown behaviors or inhibitive testing effects). Content validity--the degree to which the measurement procedure captures the true value of a participant's ability--is another consideration when evaluating measurement procedures (Gast, 2014). Like testing threats, problems with content validity may lead to underor overestimating the potency of the intervention (Johnston & Pennypacker, 2009). It is critical that the identification of EBPs for individuals with disabilities are based on studies using valid measurement procedures.

Much of the research on daily living and vocational instruction for individuals with disabilities focuses on teaching skills that occur in a chain, such as prevocational (e.g., Smith et al., 2013) and daily living skills (e.g., Godsey, Schuster, Lingo, Collins, & Kleinert, 2008). Assessors may face challenges in measuring an individual's baseline performance for a chained task given that it is inherently more complex than measuring a single discrete response (Noell, Call, & Ardoin, 2011). Therefore, mastered steps may go undetected if preceded by steps not yet mastered. Typical measurement procedures for chained tasks involve one of two procedures: singleopportunity probe (SOP) or multiple-opportunity probe (MOP; Snell & Brown, 2000).

When SOP procedures are used, the assessor presents an opportunity to perform the first step of the task. The session continues until the participant engages in an error or completes all steps correctly. If the participant makes an error, the assessor scores the error and all subsequent (not attempted) steps as incorrect. Problems exist with using SOP procedures in applied research despite compelling rationales (e.g., time and cost efficiency; Moon, Inge, Wehman, Brooke, & Barcus, 1990). From an operant view, SOP procedures can affect the participant's future responding via exposure to punishment, extinction, and reinforcement. When the evaluation ends contingent on the first incorrect response (i.e., error), future attempts to complete steps may decrease (i.e., punishing attempts). …

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