During my doctoral training in Dr. Ralph Miller's laboratory at , my interests focused on how rats use the content of learning (i.e., memory) acquired in Pavlovian conditioning treatments to make response decisions. Some of this research explored how temporal information is encoded between cues (CSs such as a tone or a light) and outcomes (USs such as footshock) during Pavlovian conditioning to form "temporal maps" (Honig, 1981) and how the maps of multiple CSs compete during conditioning. One important finding is that the degree of competition between multiple CSs is directly related to the similarity of their temporal maps (Blaisdell, Denniston, & Miller, 1998). That is, when two CSs bear the same temporal relationship to the US, more competition is seen than when the two CS-US temporal maps are different. This is surprisingly true even when the each CS-US temporal map is the same during conditioning, and one CS-US map is subsequently made different than the other (Blaisdell, Denniston, & Miller, 1999; Blaisdell, Denniston, & Miller, 2001). 

      A second line of research focused on how rats make decisions concerning whether to respond to stimuli that predict biologically significant events (e.g., food, pain, sex, and other events that serve as USs).  The basic premise of this research has been that vertebrates (e.g., rats or humans) store in memory associations between all events, such as CSs, USs, and contexts, that share close contiguity during conditioning. Within this framework, the failure to develop a conditioned response to a CS that had been paired with the US is not due to a failure to acquire a CS-US association.  Rather, this response failure reflects a 'decision' not to respond to that CS (the comparator hypothesis, Miller & Matzel, 1988).  The decision to withhold responding depends on how well the CS predicts the US relative to the predictive status of all other cues present during CS-US training.  Evidence supporting this premise comes from a variety of 'post-treatment' manipulations that do not involve the target (i.e., test) stimulus, but nevertheless alter responding to that stimulus.  Such changes in responding, also known as retrospective revaluation effects, are indicative of the targeted CS-US association having been in memory, but latently so. While in the Miller lab, I conducted a series of experiments (Blaisdell, Bristol, Gunther, & Miller, 1998; Blaisdell, Denniston, & Miller, 2001; Blaisdell & Miller, 2001; Blaisdell, Savastano, & Miller, 1999; Friedman, Blaisdell, Escobar, & Miller, 1998) that led to an important extension of the comparator hypothesis such that it accounts for many retrospective revaluation phenomena that other models cannot handle.