Suppose that a researcher begins with the traditional baseline phase, and then moves to a specific treatment (B). However, the participant’s responses indicate that the treatment has little or no effect, so the researcher modifies the treatment, creating a new phase (B1). Again, there is little or no response, so a completely different treatment (C) is started. Finally, the data show a clear change in pattern, indicating that treatment C may be effective. Thus far, the sequence of phases can be described as A-B-B1-C, and the pattern of results we have described is presented as a graph in Figure 14.9a. Although the data seem to suggest that treatment C has produced a change in behavior, there are several alternative explanations for the observed data.