Opaque models: Using drugs and dreams to explore the neurobiological basis of mental phenomena Nicolas Langlitz 1 The New School for Social Research, New York, NY, United States 1 Corresponding author: Tel.: +1-212-2295757; ext. 2443, e-mail address: langlitn@newschool.edu Abstract On the basis of four historical and ethnographic case studies of modeling in neuroscience lab- oratories, this chapter introduces a distinction between transparent and opaque models. A transparent model is a simplified representation of a real world phenomenon. If it is not pat- ently clear, it is at least much better comprehended than its objects of representation. An opa- que model, by contrast, looks at one only partially understood phenomenon to stand in for another partially understood phenomenon. Here, the model is often just as complex as its tar- get. Examples of such opaque models discussed in this chapter are the use of hallucinogen intoxication in humans and animals as well as the dreaming brain as models of psychosis as well as the dreaming brain as a model of consciousness in general. Several functions of opaque models are discussed, ranging from the generation of funding to the formulation of new research questions. While science studies scholars have often emphasized the epistemic fertility of failures of representation, the opacity of hallucinogen intoxications and dreams seems to have diminished the potential to produce positive knowledge from the representa- tional relationship between the supposed models and their targets. Bidirectional comparisons between inebriation, dreaming, and psychosis, however, proved to be generative on the level of basic science. Moreover, the opaque models discussed in this chapter implicated cosmologies that steered research endeavors into certain directions rather than others. Keywords Models, Hallucinogens, Psychedelics, Dreaming, Consciousness Historians of science have explored models created in scientists’ minds and workshops—think of neuroscientists’ imagination of the brain as a computer and of the porcelain head busts on the desks of phrenologists. This chapter examines a different practice of modeling: the use of one mind–brain state to represent another Progress in Brain Research, ISSN 0079-6123, http://dx.doi.org/10.1016/bs.pbr.2017.03.002 © 2017 Elsevier B.V. All rights reserved. 1 ARTICLE IN PRESS