The extent to which interventions are implemented as intended is called treatment integrity (TI). Given that it is unreasonable to expect 100% TI in applied settings, a through understand of TI is essential to appropriately train teachers. This understanding must include the types of TI errors that may be committed and how these effect student learning. It is essential to study TI errors because of the real-world implications for students, including eligibility decisions for special education services, which are based upon students’ responses to inventions. It is not possible to make educational decisions on intervention effectiveness unless it is clear that evidence-based practices have been implemented accurately. If TI is low, it is impossible to determine which services and interventions a student requires. Further, measuring the fidelity with which interventions are applied allows for a more thorough and accurate understanding of which components of an intervention are effective, necessary, and feasible. A broader understanding of which TI errors are most significant, as well as measuring the necessary levels of TI, will lead to more accurate information about how to implement evidence-based practices. The purpose of this study is to gain a more nuanced understanding of TI failures in the form of errors of commission and the role commission errors have on participant responsiveness (Power, 2005). This study extends the results of DiGennaro Reed et al. (2011) by including an intermediate (80%) level of TI which may more accurately represent an attainable level of TI in applied settings. For two of four students, more errors of commission were related to lower skill acquisition. For the other two students, idiosyncratic patterns of responding emerged.