Performance and Human Error

To start, it is important to understand how people act, what influences their reactions, and what causes stresses on them. The end result is to better design our technological systems so that humans can use them without abusing them (or being abused by the system). All of us can cite hundreds of cases in our own plants where people have made stupid mistakes. Why did they do that What was the result Could it have killed someone  

People make mistakes as a result of a combination of causes. Some of those causes are within the individual (e.g., not understanding how to operate a particular piece of equipment), and some are external to the individual (e.g., poor lighting on the manufacturing floor causes the operator to operate a particular piece of equipment incorrectly). 

Human performance is determined by certain factors that influence how people act. These factors are called performance-shaping factors (PSFs). PSFs are usually a complex confluence of itans that affect the operator in a system and are divided into external PSFs, internal PSFs, and stressor PSFs. PSFs can greatly affect how safely a system is operated. 

External PSFs are made up of all the conditions that an individual encounters— including the entire work environment, especially the equipment design and the written procedures or oral instructions. Three general conditions are included in external PSFs situational conditions (things that influence the individual that are plant wide or company wide, such as plant shift schedules and holidays), task and equipment characteristics (factors that are related only to a specific task or piece of equipment), and job and task instructions (factors that influence how an operator is taught to do the task). 

Internal PSFs are the factors related to the individual s previous training or experience in performing the task. Other PSFs are the individual s state of current practice or skill, personality and motivation, emotional state at the time of performing the task, and physical condition. 

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The associations of distinct detection mechartisrrts to differerrt types of errors led Thomas to propose an organic approach according to which variability in performance and human error requires parallel defense strategies and an adaptive approach and not the traditional serial protective layers as illustrated by Reason s Swiss Cheese Model. 

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