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Launched Aug 26 1996.


Project Posted 2 Jan 98


The Model

This model flow charts the general human decision process elements involved in accidents. Accidents are aborted when the decision maker or object redirects the process to the no-accident outcome. The model was developed by consolidating observations during interviews with accident investigation witnesses. Guidance for applying the model in investigations follows the model.

Human Decision Process Model

Source: FOUR ACCIDENT INVESTIGATION GAMES, Appendix V-F, Lufred Industries (now Ludwig Benner & Associates) Oakton, VA 1982

Applying the

Source: This discussion is adapted from INTRODUCTION TO INVESTIGATION, (1997) Fire Protection Publications, Oklahoma State University, Stillwell, OK. USA

This Model describes the general decision making process faced by people while interactions are occurring among people and objects during any kind of process. The model helps investigators discover and define changes, signals them emit; their detection, communication, and diagnosis; decisions required during the process, and the outcomes of those decisions.

By investigating effects of supervision, training, design, procedures, supervisory direction, and other programmer input sources related to each of these elements, investigators can link specific prior actions or "human factors" to each element.

This tracking of each decision process element enables investigators to define specific relationships among actions as problems or needs. It then enables investigators to pinpoint the places to look for concrete actions (behaviors) that will change future performance, rather than describing problems and needs in subjective, ambiguous or abstract "human factors" terms such as errors, failures, causes, malfunctions, vigilance, attention, wrong, unsafe, skill errors, latent failures, active failures, etc.

To apply this Model during investigations or interviews, identify people who appear to have had a role in the incident process. Then begin to look for changes in the process or its environment that would have created an original need for action by some person (or object) to keep the process progressing toward its intended outcome. Then follow the same process for subsequent changes unto the incident is understood and explained.

  1. When you identify a change, determine if it emitted some kind on signal that the person could have noticed. If it didn't you explore why it didn't and what effect that had on the outcome.

  2. If it did emit a signal, explore whether the person saw, heard, felt or otherwise "observed" the signal. If not, explore why not, and what effect that had on the outcome.

  3. If the person observed the signal, was the signal diagnosed correctly, in the sense that the person was able predict the consequence of the change from the signal and their knowledge of the system and its operation. If not, explore why not, and its effects.

  4. If the predicted consequences of the change were correctly identified, did the person recognize a need to do something to counter those consequences? If not, explore why not, and its effects.

  5. If so, did the person identify the choices for action that were available for successful intervention? Was this a new situation were the action had to be invented, or was this something that prior training anticipated and provided the responses to implement? In other words, was the person confronted by an adaptive or habituated response? (Here, you start to get into the person's decision making process, and potential personal judgment issues, so explore this area with empathy toward the witness, particularly for adaptive responses.)

  6. If any response actions were identified, did the person chose the"best" or an effective response to implement? If a successful response was not chosen, explore why it wasn't. To this point, you are asking for observations during an interview.

  7. If a potentially successful response was chosen, did the person successfully implement the desired action? If not, explore why not.

  8. If a suitable response was implemented, the system adapted to the change without an accidental loss or harm. If the response did not achieve a no-accident outcome, explore why it didn't. Often this leads you to discovery of invalid system design assumptions or other design problems.

After working with this model, investigators are in a much better position to describe and explain what happened when a so-called "human error" or"failure" is alleged. You will also be in a better position to identify concrete actions to improve future behaviors and performance of that system.

    Contact: Ludwig Benner, acting Principal Investigator, Ludwig Benner & Associates