In the mid 19th-century, in the early days of photography, electricity and neurology, the French physician Duchenne de Boulogne (1806-1875) undertook some of the first systematic experiments on facial muscle movement. His 1862 book ‘The Mechanism of Human Facial Expression’ used localized medical electrization to reproduce, analyze and decode faces, but also to construct, re-enact and perform emotional expressions, situating the purpose of Duchenne’s images somewhere between fine art and positivist record. In the context of photographic portraiture his pseudo-realist mixing of documentary evidence with stylized performance tells us a lot about the contemporary blending of studio conventions and scientific demonstration during which medicine and aesthetics mutually reinforce each other to create an impression of objectivity. Taking Duchenne’s depiction of ´false laughter’ as a starting point, my paper takes the frontispiece of his book as a leitmotif to raise questions about the complex politics between sitter and photographer: the double-portrait of a power-relationship between an expression-inflicting doctor and an emotion-enacting patient. Duchenne´s photographic physiology therefore matters not only because it mirrors 19th-century society, but also because it introduces a discussion on the model-photographer-viewer triangle in practices that seem to evacuate the individual sitter from the portrait in order to theatrically demonstrate an argument. The paper discusses both the different prints made for different purposes – artist’s studio, medical plate, photographic studio – and the context of the atlas of emotions.