Figure 2-1.  Three out of four accidents result from human error.  The study of human behavior is an attempt to explain how  and why humans function the way they do. A complex topic,  human behavior is a product both of innate human nature  and of individual experience and environment. Definitions  of human behavior abound, depending on the field of study.  In the scientific world, human behavior is seen as the product  of factors that cause people to act in predictable ways.  particular—some of the human factors to consider when  examining the human role are decision-making, design of  displays and controls, flight deck layout, communications,  software, maps and charts, operating manuals, checklists  and system procedures. Any one of the above could be or  become a stressor that triggers a breakdown in the human  performance that results in a critical human error. Since poor decision-making by pilots (human error) has  been identified as a major factor in many aviation accidents,  human behavior research tries to determine an individual’s  predisposition to taking risks and the level of an individual’s  involvement in accidents. Drawing upon decades of research,  countless scientists have tried to figure out how to improve  pilot performance.  The Federal Aviation Administration (FAA) utilizes studies  of human behavior in an attempt to reduce human error in  aviation. Historically, the term “pilot error” has been used  to describe an accident in which an action or decision made  by the pilot was the cause or a contributing factor that led to  the accident. This definition also includes the pilot’s failure  to make a correct decision or take proper action. From a  broader perspective, the phrase “human factors related”  more aptly describes these accidents. A single decision or  event does not lead to an accident, but a series of events; the  resultant decisions together form a chain of events leading to  an outcome. Many of these events involve the interaction of  flight crews. In fact, airlines have long adopted programs for  crew resource management (CRM) and line oriented flight  training (LOFT) which has had a positive impact upon both  safety and profit. These same processes can be applied (to  an extent) to general aviation. Is there an accident-prone pilot? A study in 1951 published  by Elizabeth Mechem Fuller and Helen B. Baune of the  University of Minnesota determined there were injury-prone  children. The study was comprised of two separate groups of  second grade students. Fifty-five students were considered  accident repeaters and 48 students had no accidents. Both  groups were from the same school of 600 and their family  demographics were similar.  The accident-free group showed a superior knowledge of  safety and were considered industrious and cooperative  with others but were not considered physically inclined.  The accident-repeater group had better gymnastic skills,  were considered aggressive and impulsive, demonstrated  Human error may indicate where in the system a breakdown  occurs, but it provides no guidance as to why it occurs.  The effort of uncovering why pilots make mistakes is  multidisciplinary in nature. In aviation—and with pilots in  2-2