On Categories, Pictures, and the Goals of Comparative Psychology

The ability to categorize objects and events has long been an object of an intense interest and rigorous research in both humans and nonhuman animals (see Lazareva & Wasserman, 2008; Mareschal, Quinn, & Lea, 2010, for reviews). Until the seminal Herrnstein and Loveland’s study (1964), most of the comparative research used simple and well-defined stimuli (e.g., 1000-Hz tone or a 450 nm light) as discriminanda. Although easily controllable, such stimuli have little relationship to the tasks faced by animals in their natural environments: After all, discriminating a hawk from a conspecific is unlikely to be based on the difference in a single wavelength or pure tone.