Naturalistic Decision Making (NDM) has been variously described as a 'movement' (Klein, 2015), a 'research community' (Gore, Flin, Stanton, & Wong, 2015), a 'framework' (Klein, 2015, Lipshitz, Klein, Orasanu, & Salas, 2001, and a 'perspective' or 'paradigm ' (Cannon-Bowers, Salas, & Pruitt, 1996). All of these labels are appropriate. As a movement, it originated in 1989 at a small, invitation-only conference in Dayton, Ohio, just one year after the shootdown of an Iranian commercial airliner by a US Navy cruiser, the USS Vincennes. The researchers invited at the 1989 meeting were concerned about applying what was known from the then-existing research on decision making to applied, realworld, contexts, such as the Vincennes tragedy. Their perception of the state of the art of decision making research at that time was that it mainly consisted of laboratory research in which novel tasks were used with inexperienced decision makers (mostly students) who were asked to make a choice among concurrently available alternatives. The findings of this body of research did not generalize to experienced decision makers who often had to make sense of a complex situation before committing themselves to a particular course of action. Thus, a movement was started that evolved into a research community that convened during biennial conferences alternating between the US and Europe. As a movement, then, NDM consists of applied researchers who are interested in how professionals make decisions in real-world situations, with the goal of supporting these professionals through decision aiding and training. The word 'naturalistic' in NDM therefore refers to real-world situations, as contrasted with laboratory situations, rather than 'natural situations' in the sense of 'taking place in nature'.As a framework or perspective, NDM is frequently contrasted with Classical Decision Making (CDM). CDM presents a view of human decision making as fundamentally flawed compared to a normative model. The normative model describes decision making as an exhaustive comparison of options, based on all available information about the options, their weights and consequences. NDM as a perspective on decision making emphasizes the study of how people use their experience to actually make decisions in field settings, rather than how they are supposed to make decisions. In the NDM framework, professional decision making behavior is an adaptation to uncertain, dynamic, environments, shifting, ill-defined or competing goals, time stress, high stakes, multiple eventfeedback loops, ill-structured problems, multiple players, and organizational goals and norms that must be aligned with the decision maker's personal goals and norms (Orasanu & Connolly, 1993). Given these task constraints, decision making does not usually allow for an exhaustive comparison of options, as CDM would claim. The adaptations to these task constraints are usually viewed as successful (Kahneman & Klein, 2009), as long as experts can bring to bear their knowledge and experience in order to m...