Several methodologies are available to evaluate how animals discriminate and perceive stimuli. These methodologies are described herein, and the kinds of questions that can be addressed with each technique, and its strengths and limitations,are addressed. De ction and discrimination studies are described that measure animal abilities, followed by classification and judgment studies that measure animal proclivities.  The choice of methodology is a consideration in experimental design, because the format of the question can direct, and sometimes define the answer. The experiments discussed emphasize that animals have multiple processing modes available to them that they use to classify stimuli. Detection and discrimination experiments may tap into one of those modes, while categorization and judgment experiments may address a different mode. A feature of these experiments is that they reduce the extent to which we view animal perception and cognition as distinct from human perception and cognition. Several methodologies are available to evaluate how animals discriminate and perceive stimuli. These methodologies are described herein, and the kinds of questions that can be addressed with each technique, and its strengths and limitations, are addressed. Detection and discrimination studies are described that measure animal abilities, followed by classification and judgment studies that measure animal proclivities. The choice of methodology is a consideration in experimental design, because the format of the q estion can direct, and sometimes define the answer. The experiments discussed emphasize that animals have multiple processing modes available to them that they use to classify stimuli. Detection and discrimination experiments may tap into one of those modes, while categorization and judgment experiments may address a different mode. A feature of these experiments is that they reduce the extent to which we view animal perception and cognition as distinct from human perception and cognition.