Decision criteria do not shift: commentary on Mueller and Weidemann (2008)

The effects of base rates and payoffs on the shapes of rating receiver operating characteristic curves are inconsistent with the basic assumptions of signal detection theory (SDT), in particular the notion of a shifting decision criterion. Mueller and Weidemann (2008) propose that these unexpected phenomena are not due to problems with the decision-criterion construct but are instead due to two compounded effects: instability of the decision criterion across trials, and even greater instability in the flanking criteria that determine which confidence rating will be reported. There are several problems with the authors' decision-noise hypothesis. First, even if their hypothesis about decision noise were taken for granted, the key feature of the ratings data that rejects the SDT model would remain a mystery. Second, the same violations of SDT that are exhibited in the ratings paradigm are also exhibited in the yes-no detection task when response time is substituted for confidence as a basis for analysis. Finally, the decision-noise hypothesis predicts that sensitivity will increase when one source of this variation-the response on a previous trial-is controlled for. This prediction was consistently violated in both the yes-no and ratings conditions of Mueller and Weidemann's experiment. In an Addendum, we respond to Weidemann and Mueller's (2008) reply to this Comment.