No theory forbids me to say "Ah!" or "Ugh!", but it forbids me the bogus theorization of my "Ah!" and "Ugh!" - the value judgments. - Theodor Julius Geiger (1960)

Human Perception and Safety

In safety management, attributing errors solely to 'human error' overlooks systemic issues. Explaining failures as 'loss of situation awareness' neglects larger contextual or environmental factors contributing to errors. Likewise, attributing automation surprises to 'human error' limits solutions by overlooking systemic design flaws in systems.  

The research of James Gibson (1904-1979) redefined human perception. His work challenged traditional stimulus-response models. Gibson emphasized organisms' immediate understanding of the environment without complex cognitive processing. William Mace summarized Gibson’s main principle as: ‘Ask not what’s inside your head, but what your head’s inside of’. This challenges the focus on internal mental processes and stresses the role of the external environment in shaping human behavior and perception.

The incorporation of human factors meant a shift in focus from changing individual behavior (behaviorism) to modifying systems and contexts. This approach:

- aims to understand how systems influence behavior and

- implements error-tolerant design to prevent errors at the system level.

By altering environments and systems, human factors indirectly influence behavior, crucial for safety management, shifting from addressing individual errors to designing systems that encourage safer behavior.

Cognitive systems engineering redefines error by examining interactions between people and systems. It challenges the view that errors stem solely from individuals, and studies joint cognitive systems to uncover vulnerabilities affecting overall system output.  


Dekker, S.W.A. (2019), Foundations of Safety Science - A Century of Understanding Accidents and Disasters, Boca Raton FL: CRC Press.

Mace, W.M. (1977), James J. Gibson’s Strategy for Perceiving: Ask Not What’s Inside Your Head, but What Your Head’s Inside of, in: Shaw, R., Bransford, J. (1977), Perceiving, Acting, And Knowing – Toward an Ecological Psychology, Hillsdale, NJ: Lawrence Erlbaum Associates.