This chapter presents a range of experiments, all concerned in one way or another with what goes on in a pigeon’s head when it discriminates objects in the visual world. The experiments are also linked by their common use of reaction time (RT) measurements to uncover those discriminative processes. The chapter begins with evidence that pigeon RT-intensity data differ in two interesting ways from comparable human data and that at least one of these differences may expand on evidence for a retinal rod–cone interaction that was first discovered in pigeons and later confirmed in humans. The discussion then moves to higher-level processes that are reflected in the speed with which a searcher discovers a concealed target. In pigeons, as in humans, search RTs provide information on the strategies used to detect perceptual objects, on the features that characterize those objects, and on the role of expectation in the detection process. The last section of the chapter summarizes three models that use RT distributions to distinguish and quantify several further aspects of discriminative control.