"Systems" Perspective of Human Factors and Usability Analysis

For human factors/ergonomic/usability analysis, it is useful to consider the "system" to involve one or more individual users plus the technology that they are using to perform tasks of interest. The human-technology "interface" thus becomes a connection between subsystems. The modes of transfer between subsystems may include two types:

• undirectional information transfer, normally with a sensory channel (auditory, visual, tactile) receiving information from a motor channel of another person (speech, eye-head-hand-torso postural orientation, hand manipulation) or from the environment.
• bidirectional power transfer, normally through physical contact, where there is instantaneous 2-way force-velocity transmission (e.g., see discussion of Extended Physiological Proprioception)

This is an "interface port" conceptual framework. There are many other "systems" concepts that can be of value for usability analysis. For instance, there are "human operator" models for goal-directed pursuit tracking tasks that represent the human response to a stimulus as a time lag plus low-pass filter. This is simplistic but can be useful for analysis or design within a controlled environment such as a cockpit. There is also the HAAT conceptual model that considers performance of the human and assistive technology as a system. While a simplification, for a reasonably well-defined type of activity, performance of the combined intrinsic and extrinsic enablers can be a useful tool for analysis.

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