Editor’s Note: Studying performance errors in policing can be difficult for researchers who cannot ethically replicate the dangerous conditions present in lethal force encounters. To overcome this limitation, researchers routinely consider evidence derived from other professions and industries (e.g., aerospace (Airbus), aeronautics (NASA), pharmaceutical, occupational safety and health, medical, industrial engineering, and transportation).
Recent events have prompted readers to request references for slip/capture error research. For this reason, I added a reference list at the end of this article that begins with two articles addressing Taser/Weapon errors (“Taser/Weapon Confusion”). The remaining list includes citations to research explaining performance errors generally and slip/capture errors specifically.
How does an officer draw and fire their pistol when it is clear they intended to draw and discharge their Taser?
When an officer first learns to draw their pistol, it may require intense focus to defeat the holster’s retention features, secure a proper grip, maintain a safe orientation, and efficiently draw and capture a sight picture. However, with sufficient practice, this process will be performed with little cognitive effort or awareness. This ability to draw a weapon or perform any skilled task without the need for focused attention or “cognitive control” is referred to as “automaticity.”
For police, automaticity frees up their “cognitive load” for more effective decision-making and allows them to remain externally focused on threat assessments, changing environmental conditions, and communication efforts. Unfortunately, the repetitive performance that leads to automaticity can also play a role in a common performance error known as a “capture error.”
A “capture error” can occur when an infrequent action like drawing a Taser is non-consciously substituted by a similar, more familiar, and more practiced action—like drawing a firearm. Research has shown that people are particularly susceptible to this type of error when they are occupied by other mental processes. For police, these processes might involve time-compressed threat assessments, the need for immediate action, or simultaneous efforts to communicate—including verbal warnings and de-escalation attempts.
These are Resilient Errors
Capture errors fall under the category of performance errors known as “slips.” Slips occur when someone has the right intention but fails in its execution (and this failure cannot be attributed to some chance intervention).
Human factors researchers have observed that slip errors can have severe consequences. They are difficult to reduce—even with training, visual cues, or increased motivation. Experts and novices are susceptible to slip errors. They are not the result of a lack of knowledge or expertise but instead occur from a temporary failure of working memory.
Efforts to reduce errors by inserting visual cues, weight disparities, and audible warnings can be affected by attentional limitations. Humans perceive what they pay attention to, and during critical incidents, their attention may be involuntarily pulled to the most “salient” stimulus in the environment. Often, that is the person, object, or action perceived to pose the greatest threat.
When a person is intently paying attention to what they perceive as a threat, it is expected that they will not perceive the other stimulus around them. That includes factors that we would expect someone to notice under calmer circumstances—factors like the weight, shape, and color of a Taser as compared to a full-size firearm.
To further complicate things, human performance researchers have highlighted other processes that should be considered when looking to understand why the physical characteristics of a Taser may not always be sufficient to distinguish it from a pistol. Neuroscientist Daniel Wolpert has explained that once our brain predicts an action’s sensory consequences, we “subtract them off” and are not aware of them. Similarly, Dr. Richard Schmidt noted that once the brain concludes (even erroneously) that correct action is being executed, it can disregard feedback that might otherwise indicate you’ve selected the wrong tool or weapon.
It’s Not Just the Police: Broad Professional Interest in Performance Errors
The police are not unique in their susceptibility to performance errors. Nearly every industry involving the interaction of humans with machines has studied performance and decision-making errors. In addition to policing, the medical, engineering, and aeronautical professions continue to study and build into their products and processes ways to prevent, reduce, or mitigate the consequences of errors.
The World Health Organization produced a manual that includes a chapter dedicated to the classification and prevention of common psychomotor medical errors. In response to the estimated 150,000 annual deaths caused by medical errors, doctors, pharmacists, and nurses are trained to recognize error-inducing factors and to implement error-reducing processes.
The aerospace industry, including Airbus, has extensively focused on airplane design and control configuration to avoid lapses, slips, and captures—three of the most common psychomotor performance errors.1
Those who would argue that science does not support the theory of slip errors or capture errors will need to contend with aerospace (Airbus), aeronautics (NASA), pharmaceutical, occupational safety and health, medical, industrial engineering, and transportation industries.
Conclusion: Mitigating Taser / Weapon Confusion
Although extensive research has gone into understanding human error, it will never be enough to prevent them entirely. Humans will always make errors. Even so, efforts to prevent errors, interrupt errors, or mitigate the consequences of errors—including engineering and product design solutions—are often studied and implemented.
Training the mental and physical processes involved in a task, including training to maintain optimal arousal states, may also mitigate the frequency of error during critical incidents, even if they are not reasonably expected to eliminate the error.
When looking at Taser / Weapon confusion cases, it bears mentioning that Taser/ Weapon confusion is an extremely low frequency, high consequence event. Still, it has been reported that these cases have occurred 18 times in the U.S. since 2001. We can observe in each of these cases that the officers drew the Taser with their dominant hand (the same hand an officer would routinely use to draw their firearm). This was apparently the case even when the officers conducted a cross draw.
To mitigate the risk of Taser / Weapon confusion (drawing a firearm when the officer intends to draw a Taser), police professionals and Taser manufacturer Axon have recommended that officers carry the Taser on their nondominant side. This position may prompt officers to draw and deploy the Taser with motor movements that are distinct from those required to draw and fire their pistols.
It has been suggested that the color of the Taser and the weight of the Taser can mitigate the risk of weapon confusion. However, as mentioned above, there is evidence that these factors may be insufficient to overcome the capture errors, the attentional limitations, and the suppressive cognitive processes that can occur during time-compressed critical incidents.
Although we are unaware of a documented Taser / Weapon confusion incident that involved drawing the Taser with the nondominant hand, we recognize that even this mitigation process (or vest-carrier holster option) may come with its own performance and safety trade-offs.
As the police profession considers ways to mitigate the risk of Taser / Weapon confusion, the most promising solutions may be found in a holistic approach.
A better understanding of human performance under stress, more effective training, and modified equipment design and functionality are solutions extensively studied and applied in the medical and aviation industries. Policing should continue to draw on the lessons learned from these and other professions hoping to manage human error.
Bonus: Examples of Common Capture Errors
As previously mentioned, a capture error occurs when a less frequently occurring behavior is automatically substituted by a more practiced, familiar behavior. The following examples are provided for readers hoping to better understand the concept of capture errors.
Repeatedly reaching for a gear shift, ignition, or turn signal in a new or rented car only to find these controls are no longer where you expected to find them.
Even before the widespread use of Tasers, many police agencies trained and equipped officers to avoid psychomotor performance errors. Departments warned, trained, and required officers to carry the same make and model handgun when on-duty and off-duty to prevent errors in the operation of the holster and weapon during stressful situations. Officers who change holsters are cautioned to practice with the new holster to reduce the likelihood of slipping back into the previous retention release and draw performance patterns. If this slip error occurs during a critical incident, officers may be unable to draw from their new holster effectively.
After transitioning from the older power brakes to the new automatic brakes, police officers in the 80s were involved in an increased number of crashes during high-speed driving because they reverted to their more familiar braking habits under stress. In doing so, the officers effectively defeated the automatic brakes’ operation and lost control of their vehicles. This error occurred despite the officers knowing the new brakes required a different manipulation.
Driving on the left side of the road in a foreign country requires additional focused attention for U.S. drivers. In anticipation of performance and decision errors, drivers new to left-side driving are warned that emergency corrective action that might work in the U.S. may be precisely the opposite of what is effective when left-side driving. During distracted or emergency circumstances involving immediate response, the most frequently practiced and executed performance can overtake (“capture”) the newer, less practiced, and more appropriate solution.
In the medical world, capture error was identified and extensively studied due to nurses incorrectly programming a new infusion pump model. Because the sequence of steps was similar but not identical to the older, more familiar pump, errors occurred. These errors were more pronounced when the nurse was distracted, in a hurry, or otherwise preoccupied.
Dr. James Reason includes the following examples of capture errors: after moving a clock from one wall in a room to another wall, automatically and repeatedly looking at the old location; continually looking in the old location after moving the location of dishes in a kitchen or tools in workroom; automatically reaching for your keys in the pocket you most routinely store them.
Dr. Richard Schmidt, 40 years in the psychology department at UCLA and chief author of Motor learning and Performance, frequently lectured on the concepts of slip and capture errors. He gave examples and testified in court to how these errors could result in automobile accidents involving pedal misapplication errors. Pedal misapplication errors occur when a driver steps on the accelerator when intending to apply the brakes or simultaneously steps on the accelerator and the brake. A study by the National Highway Traffic Safety Administration reports that accidents involving pedal error occur approximately 16,000 times a year in the United States. Without time or attentional resources to critically analyze the problem, drivers may unintentionally push on the gas pedal (even slam on the pedal!), believing it to be the brake.
Articles on TASER/Firearm Error
- Blake, D. (2021). 3 Recommendations to mitigate TASER/firearm ‘capture’ errors. Police1, The Science of Training. https://www.police1.com/police-training/articles/3-recommendations-to-mitigate-taserfirearm-capture-errors-8BR8tWo27y59znpP/
- Martin, J. A. (2016, September). Applied human error theory: A police TASER-confusion shooting case study. In Proceedings of the Human Factors and Ergonomics Society Annual Meeting (Vol. 60, No. 1, pp. 475-479). Sage CA: Los Angeles, CA: SAGE Publications. https://doi.org/10.1177/1541931213601108
Relevant Human Error Research
- Ament, M. G. A. (2011). The role of goal relevance in the occurrence of systematic slip errors in routine procedural tasks. (Doctoral dissertation, UCL (University College London)).
- Anu, V., Walia, G., Hu, W., Carver, J. C., & Bradshaw, G. (2016, October). Using a cognitive psychology perspective on errors to improve requirements quality: An empirical investigation. In 2016 IEEE 27th International Symposium on Software Reliability Engineering (ISSRE).
- Back, J., Blandford, A., & Curzon, P. (2007, August). Slip errors and cue salience. In Proceedings of the 14th European conference on Cognitive ergonomics: invent! explore! (pp. 221-224).
- Chapanis, A. (1999). The Chapanis chronicles : 50 years of human factors research, education and design. Aegean.
- Dekker, S. (2014). The field guide to understanding ‘human error’ (Third edition. ed.). Ashgate.
- Evans, R. B. (1990). William James, “The Principles of Psychology,” and Experimental Psychology. The American Journal of Psychology, 103(4), 433-447. https://doi.org/10.2307/1423317
- Frese, M., & Altmann, A. (1989). The treatment of errors in learning and training. Developing skills with information technology, 65.
- Hofmann, D. A., & Frese, M. (2011). Errors, error taxonomies, error prevention, and error management: Laying the groundwork for discussing errors in organizations. In Errors in organizations (pp. 18-60). Routledge.
- Holland, K., Sun, S., Gackle, M., Goldring, C., & Osmar, K. (2019). A qualitative analysis of human error during the DIBH procedure. Journal of medical imaging and radiation sciences, 50(3), 369-377.e361..
- Holland, K., Sun, S., Gackle, M., Goldring, C., & Osmar, K. (2019). A Qualitative Analysis of Human Error within the DIBH Procedure. Journal of Medical Imaging and Radiation Sciences, 50(2), S3.
- Lewis, C., & Norman, D. A. (1995). Designing for error. In Readings in Human–Computer Interaction (pp. 686-697). Morgan Kaufmann.
- Lopes, M. E. R. F., & Forster, C. H. Q. (2013). Application of human error theories for the process improvement of Requirements Engineering. Information Sciences, 250, 142-161.
- Mambrey, V., Vu-Eickmann, P., Angerer, P., & Loerbroks, A. (2021). Associations between Psychosocial Working Conditions and Quality of Care (ie, Slips and Lapses, and Perceived Social Interactions with Patients)—A Cross-Sectional Study among Medical Assistants. International journal of environmental research and public health, 18(18), 9693.
- Martin, J. A. (2016). Applied Human Error Theory:A Police Taser-Confusion Shooting Case Study. Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 60(1), 475-479. https://doi.org/10.1177/1541931213601108
- Najar, S. A., & Sanjram, P. K. (2021). Driving errors and gaze behavior during in-vehicle object and spatial distractions. Journal of Transportation Safety & Security, 13(4), 381-413.
- Norman, D. A. (1981). Categorization of action slips. Psychological review, 88(1), 1.
- Reason, J.T. (1990). Human Error. Cambridge University Press, Cambridge. https://doi.org/10.1017/CBO9781139062367
- Sellen, A. J., & Norman, D. A. (1992). The psychology of slips. In Experimental slips and human error (pp. 317-339). Springer, Boston, MA.
- Sutcliffe, A., Galliers, J., & Minocha, S. (1999, June). Human errors and system requirements. In Proceedings IEEE International Symposium on Requirements Engineering (Cat. No. PR00188) (pp. 23-30). IEEE.
- Taylor, P.L. (2019). Human error in police involved shootings. State University of New York at Albany.
- Taylor, P. L. (2019). Beyond false positives: a typology of police shooting errors. Criminology & Public Policy, 18(4), 807-822.
- Vickers, J. N. (2007). Perception, cognition, and decision training : the quiet eye in action. Human Kinetics.
- Wickens, C. D., Hollands, J. G., Banbury, S., & Parasuraman, R. (2015). Engineering Psychology and Human Performance (4 ed.). Psychology Press. https://doi.org/10.4324/9781315665177
- See Human Error. James Reason. Cambridge: Cambridge University Press (1990).