Introduction: lay participation in the history of scientific observation.

Why and how have lay people participated in scientific observation? And on what terms have they collaborated with experts and professionals? We have become accustomed to the involvement of lay observers in the practice of many branches of science, including both the natural and human sciences, usually as subordinates to experts.1 The current surge of interest in this phenomenon, as well as in the closely related topic of how expertise has been constructed, suggests that historians of science can offer a valuable contribution to these vital questions. A historical approach to lay participation allows us to better understand the making of expert-lay relations in science, and it offers a broader, long-term perspective on contemporary debates about that boundary. This topical issue on lay participation in science, which derives from a workshop held at the Max Planck Institute for the History of Science in 2007, focuses attention on observation. Recently, historians have begun to explore more fully the significance of observational practices of all kinds in science (Daston 2008; Daston and Lunbeck 2011). Lay people have a long and varied history of participation in scientific observation, some contributing their skills and experiences to help produce knowledge, others engaging with science in public settings. Not only can the exploration of the historical development of lay participation in scientific observation help us better understand the past, it can also help us make sense of present-day debates about the roles of lay people in science.2 Moreover, placing the growing collection of recent examples of lay-expert interactions among a diverse set of historical examples spanning the past three centuries allows us to understand what is peculiar or distinctive about present-day configurations of how lay people are involved in scientific observation.