The Role of Mental Models

The operator s model of the system will be based partly on formal training created from the designer s model and partly on experience with the system. The operator must cope with the system as it is constructed and not as it may have been 

Operators continually test their models against reality 

Operators use feedback to update their mental models of the system as the system evolves. The only way for the operator to determine that the system has changed and that his or her mental model must be updated is through experimentation To learn where the boundaries of safe behavior currently are, occasionally they must be crossed. 

Experimentation is important at aU levels of control [166]. For manual tasks where the optimization criteria are speed and smoothness, the limits of acceptable adaptation and optimization can only be known from the error experienced when occasionally crossing a limit. Errors are an integral part of maintaining a skill at an optimal level and a necessary part of the feedback loop to achieve this goal. The role of such experimentation in accidents cannot be understood by treating human errors as events in a causal chain separate from the feedback loops in which they operate. 

At higher levels of cognitive control and supervisory decision making, experimentation is needed for operators to update procedures to handle changing 

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