Abstract
This article offers a canine history of the "critical period" concept, situating its emergence within a growing, interdisciplinary network of canine behavior studies that connected eugenically minded American veterinarians, behavioral geneticists, and dog lovers with large institutional benefactors. These studies established both logistical and conceptual foundations for large-scale science with dogs while establishing a lingering interdependence between American dog science and eugenics. The article emphasizes the importance of dogs as subjects of ethological study, particularly in the United States, where some of the earliest organized efforts to analyze canine behavior began. Further, the article argues that the "critical period" is important not only for its lasting prominence in multiple fields of scientific inquiry, but also as a historiographical tool, one that invites reflection on the tendency of historians to emphasize a particular narrative structure of scientific advancement.