The problems of double-checking and lack of operator independence in barrier management

Is double-checking effective? How independent can human actions be when part of a verification activity?

Not much to say here – I found the following excerpts from the CIEHF’s white paper on “Human Factors in Barrier Management” interesting, discussing the potentially misaligned assumptions of independence in verifications.

They cover the limitations of independence, how the checker knows whose work that they are checking. If the checker believes the operator’s work is reliable, then the checker assumes that the operator’s performance will be correct.

Essentially, the checker sees what they expect to see.

And the impact of checking may not be as great as is expected. The white paper also lists some suggestions on checking and independence in barrier systems.

They further argue that “If a single condition or event (such as relying on the same operator to cover a number of barriers) could defeat or seriously degrade the performance of more than one barrier element, then those elements are not independent; they would actually represent only a single barrier or element.”

This potentially false sense of safety from double-checks has been termed the ‘fallacy of social redundancy’.

Interestingly, a study I summarised recently systematically reviewed the research on double-checks.

One aviation study of double-checking using a simulator found no significant difference in performance between single pilot and dual-pilot operations regarding automation failures.

Another study, using uni students, studied automation bias in a computer simulation tracking of tasks involved in commercial flying. Individuals and pairs were equally likely to miss events and fail to respond to system irregularities.

They concluded that the extant research “do not support the adage that two people are better than one” and that “the performance of two people checking was not superior to one person in detecting errors”.

Refs:

1. IEHF. (2016). Human factors in barrier management. (Both attached images)

2. McMullan, R. D., Urwin, R., Wiggins, M., & Westbrook, J. I. (2023). Applied Ergonomics, 106, 103906.

Links:

IEHF white paper: https://ergonomics.org.uk/resource/human-factors-in-barrier-management.html

Double-checking study: https://www.linkedin.com/pulse/two-person-checks-more-effective-than-one-person-tasks-ben-hutchinson/

LinkedIn post: https://www.linkedin.com/posts/benhutchinson2_is-double-checking-effective-how-independent-activity-7183208096310206464-hB03?utm_source=share&utm_medium=member_desktop