Most studies of decision making, based on artificial tasks assigned in laboratory settings, view people as biased and unskilled. Gary Klein is one of the developers of the naturalistic decision making approach, which views people as inherently skilled and experienced and documents human strengths and capabilities that so far have been downplayed or ignored. Since 1985 Klein has conducted fieldwork to find out how people tackle challenges in difficult, nonroutine situations. Sources of Power is based on observations of humans acting under such real-life constraints as time pressure, high stakes, personal responsibility, and shifting conditions. The professionals studied include fire-fighters, critical care nurses, pilots, nuclear power plant operators, battle planners, and chess masters. Each chapter builds on key incidents and examples to make the description of the methodology and phenomena more vivid. In addition to providing information that can be used by professionals in management, psychology, engineering, and other fields, the book presents an overview of the research approach of naturalistic decision making and expands our knowledge of the strengths people bring to difficult tasks.