The article examines literature from two medical discussions. The first discussion focuses on the concepts of imbecility and idiocy and took place in the late 19th and early 20th centuries in Western Europe and the United States. The second discussion focused on the diagnosis of encephalitis lethargica in children during the 1920’s. The previous discussion of imbecility heavily influenced the diagnosis of encephalitis lethargica and occupied a seminal place in the history of defining child behavior in medical terms. This diagnosis served as a specific disease category for children who demonstrated unconventional behavior in a variety of social contexts. The analysis argues that the discussion of encephalitis lethargica began a psychiatric research modality that sought to find neurological bases for childhood deviance, typified by the contemporary discussion of ADHD. 43 references (Author abstract modified)