The field of clinical animal behavior has a growing scientific basis, with three main paradigms having different perspectives on the assessment of animal emotion. The Behavioral approach, grounded in classical behaviorism, makes little reference to emotion in assessment, despite covert recognition of its importance. The Medical approach, drawing on human psychiatric approaches, emphasizes the importance of physical evidence (behavior descriptions and physiological parameters) for validation of diagnoses centred on abnormality and disorder. The more recent Psychobiological approach synthesizes affective neuroscience, ethology and psychology to propose a systematic and rational framework for making inferences about emotion, that result in the construction of testable (falsifiable) hypotheses relating to four domains derived from component process theory using field-based evidence.