Human Performance Theories And SOPs: Human Error Prevention In Manufacturing

November 6, 2023
November 2023
November 6, 2023
Pharmaceutical Online

Standard operating procedures (SOPs) are the backbone of any manufacturing operation, serving as the blueprint for how tasks should be performed to ensure quality and safety. However, SOPs are often viewed as mere documents to be followed, rather than as dynamic tools that can be optimized for human performance. Drawing on human performance theories from experts like Sidney Dekker, this article explores how to create, review, and train on SOPs with human error prevention in mind. It also discusses how manufacturing and quality teams can collaborate to improve oversight during task execution.

Human Performance Theories: A Brief Overview

Human performance theories emphasize that human errors are often the consequence, not the cause, of systemic issues.4 These theories advocate for a holistic approach that considers the interaction between humans and the systems they operate within. A great term for this is reciprocal determinism. What it essentially boils down to is our behavior, our environment, and our personal characteristics, such as our thoughts and feelings, all interact and influence each other in a two-way, "reciprocal" manner. For example, knowing that an environment in disarray negatively affects performance can lead to changes like better signage, enhanced housekeeping, or improved lighting, making it easier to avoid mistakes. By understanding the underlying factors that contribute to errors, organizations can create more resilient systems that are better equipped to prevent errors before they occur.

Creating SOPs: A Human-Centric Approach

Operators are the ones who will be executing the tasks outlined in the SOPs. This is obvious to anyone in our industry; however, it is surprising how often they are handed a new or updated SOP without ever getting to provide their input. Their insights are invaluable in identifying potential pitfalls, ambiguities, or complexities that could lead to errors. Involving them in the SOP creation and revision process ensures that the procedures are practical, understandable, and tailored to the actual conditions on the manufacturing floor. Some of you may be reading this and thinking, yes this is ideal but how do we avoid creating more error traps by pulling away our operators to design and revise procedures? Don’t worry, I have some suggestions for you!

  • Scheduled Briefings: Allocate specific time slots where operators can meet with SOP authors to provide their input. This could be during less busy hours or shift changes.
  • Digital Surveys and SOP-specific Spreadsheets: Use digital platforms to collect feedback. Operators can fill these out during their downtime.
  • Feedback Boxes: Place physical or digital "feedback boxes" near workstations where operators can drop suggestions or comments. Providing operators with a camera gets you a gold star, as they can take pictures of complex tasks or setups, which can be added directly into an SOP.
  • Job Rotation: Temporarily rotate some operators into the quality or SOP development team to provide direct input.
  • Virtual Meetings: Use video conferencing tools to facilitate quick meetings that don't require operators to leave their stations.

When operators are asked to support SOP generation and revision, they can follow the acronym PRIDE, which I developed as a guide for what kinds of information to provide to the authors.

P: Process Understanding

R: Risks and Challenges

I: Improvements

D: Details and Specifics

E: Exceptions and Special Cases

Let’s see what this looks like in the real world with an example around the SOP for disinfection of materials during movement into the cleanroom.

P: Process Understanding

Operators can start by outlining the current process of how materials are moved and disinfected. They can describe the steps involved, the equipment used, and the timing required for each step.

Example: "We currently use a cart to move materials from the receiving area to the cleanroom. Before entering, we wipe down the cart and materials with a disinfectant solution. This takes about 15 minutes."

R: Risks and Challenges

Operators can identify potential risks or challenges in the current process. This could include areas where contamination is most likely to occur or where the process slows down.

Example: "The wheels of the cart are hard to clean thoroughly and could be a potential source of contamination. Also, the 10-minute hold time for disinfection can cause delays and backups at the airlock."

I: Improvements

Operators can suggest improvements based on their hands-on experience. These suggestions can be both for the process and for the SOP document itself.

Example: "We could obtain additional carts, so that there is one kept on either side of the demarcation area in the airlock. This would alleviate some of the disinfection time since only the materials would have to be disinfected and moved over to the cart dedicated to the cleanroom area."

D: Details and Specifics

Operators can provide specific details that may not be obvious but are crucial for the SOP's effectiveness. This could include tips, tricks, or specific observations.

E: Exceptions and Special Cases

Finally, operators can point out any exceptions or special cases that the SOP should account for. This could include what to do in case of an emergency, equipment failure, or other non-standard situations.

Example: "Since we typically don’t have the SOP out and open during material transfer, signage, dedicated locations for the carts, timers, and other tools should be implemented in the appropriate areas, to ensure the right behaviors are followed."

Collaboration with the quality department while working through the PRIDE steps is a great way to improve relations between the departments, prepare quality representatives for supporting the process, and ensure the SOP is built with quality in mind. The role of quality is as follows:

  • Compile Information: Partner with the authors to collect the PRIDE-based feedback from operators.
  • Analyze and Integrate: Analyze the feedback for common themes or critical points that may even be integrated into other procedures or processes.
  • Review: Help lead a review session where operators can go through the revised SOP to ensure their feedback has been accurately incorporated.
  • Training: Once the SOP is finalized, be present and involved in training sessions to ensure all operators understand the new procedures.

By using the PRIDE acronym in this manner, you can ensure that the SOP is not only comprehensive and effective but also practical.

Simplicity, Clarity, And Consistency

SOPs should be as simple and clear as possible. Complex language, jargon, or convoluted steps can confuse operators and increase the likelihood of errors. Two of the top eight error precursors, or prerequisites to error, as defined by the International Nuclear Database under Task Demands are “Interpretation Requirements” and “Lack of or unclear standards.”3 Expecting operators to process long paragraphs and identify their specific action or pull from memory greatly increases cognitive load. Use plain language and straightforward instructions to make the SOPs easily comprehensible. Think IKEA: short, action-verb focused instruction, with visuals when feasible.

Maintaining a uniform style, format, and structure is crucial when crafting effective technical procedures, not just within a single document but across multiple ones as well. Inconsistencies can again lead to misunderstandings, as users may think that different presentations imply different meanings. A consistent approach eliminates the need for users to spend extra effort deciphering the presentation style for each section, allowing them to focus solely on executing the instructions. To go above and beyond, create a foundation of specific terminology that is used across multiple documents, and avoid synonyms merely for the sake of introducing variation. This will alleviate the strain on information processing.

Below are additional human performance considerations with regard to format and layout of SOPs:

  • Limit the number of physical actions to be taken in one instruction to two or less. If multiple actions are required, offer a checklist. Additionally, take a risk-based approach to determine if a verifier should be present during each action or after all actions are complete.
  • Bolding, colors, and other visual cues are integral at critical points in a document. For example, color code the entry location of information that needs to be transcribed from one page to another or bold equipment or separate procedural references.
  • Ensure any step references or references pointing to external documents are accurate.
  • Include attention activators when there is a need to record data or obtain signoffs in an associated processing document or logbook. This can be as simple as an icon next to the instruction.
  • Avoid ambiguous words, e.g., "Connect the tubing to valve" should be rephrased as "Connect the outlet tubing to valve XYZ," where XYZ is the specific valve name or number.
  • Avoid vague adjectives (words modifying nouns) and adverbs (words modifying verbs) that are subject to interpretation. Specify quantities whenever possible (e.g., "Drain the tank at 10 gallons/minute" is preferable to "Drain the tank slowly."

Work Environment

If we look at the top error precursors associated with the Work Environment, “Distractions/Interruptions” and “Confusing Displays and Controls” are among those listed.3

In an experiment conducted by Alessandro Acquisti, a professor of information technology, and psychologist Eyal Peer at Carnegie Mellon, the impact of interruptions on cognitive performance was measured. Participants were divided into three groups: Control, Interrupted, and On High Alert. All were given a cognitive skill test involving reading a passage and answering questions. The Control group was not interrupted, while the other two groups were told they might receive an instant message at any moment. During the first test, the Interrupted and On High Alert groups were actually interrupted twice. In the second test, only the Interrupted group faced interruptions, while the On High Alert group awaited an interruption that never came. The results showed that the groups that were interrupted performed 20% worse than the Control group. The study concluded that interruptions, along with the mental preparation for them, significantly impaired cognitive performance, enough to turn a B-minus student into a failing one.2

Knowing this, how can we improve our SOPs to mitigate potential human error?

Distractions and Interruptions: In a busy manufacturing setting, distractions and interruptions are almost inevitable. These could range from sudden equipment alarms to colleagues or auditors asking questions during a critical task.

SOP Mitigations:

  • Designated Quiet Zones: SOPs could specify areas or zones where distractions must be minimized. For example, a quiet zone could be established around areas where tasks requiring high concentration are performed. Signage can be posted to provide outsiders with a cue to avoid any interruptions during the critical task.
  • Task Segmentation: SOPs can break down complex tasks into smaller segments, with built-in pauses for operators to deal with interruptions safely without losing their place in the procedure.

Confusing Displays and Controls: Complex machinery often comes with equally complex controls and displays, which can be overwhelming for operators and increase the likelihood of errors.

SOP Mitigations:

  • Standardized Interfaces: SOPs can mandate the use of standardized interfaces across different pieces of equipment to reduce cognitive load.
  • Step-by-Step Guidance: SOPs can include a step-by-step guide for navigating complex displays, perhaps even incorporating visual aids like screenshots or diagrams.

Human factors engineering (HFE) also can be integrated into SOPs to mitigate these error precursors effectively.

  • Cognitive Aids: HFE principles advocate for the use of cognitive aids like checklists and flowcharts. These can be incorporated into SOPs to guide operators through complex tasks, reducing the cognitive load and minimizing the impact of distractions.
  • User Testing: Before finalizing SOPs, they can be tested with actual operators in simulated environments. This allows for real-world testing of how well the SOPs mitigate distractions and guide the operator through confusing displays.
  • Feedback Loops: Both HFE and effective SOPs benefit from continuous improvement. SOPs can include a mechanism for operators to report difficulties, distractions, or errors, which can then be analyzed to make further improvements.
  • Role Clarity: Clear SOPs, designed with human factors in mind, can help eliminate role confusion, which is often a significant source of stress and error. When everyone knows their role and what is expected, the chances of errors due to distractions or misunderstandings are reduced.

Avoiding Procedural Overspecification

It’s important to note that adding more procedures doesn't necessarily lead to better compliance or safety. Often, the knee-jerk reaction to a failure is to create more detailed rules targeting the specific issue at hand, a practice known as procedural overspecification.1 While this may seem like a good safety investment, it often widens the gap between written procedures and actual practice. Rules can become increasingly disconnected from the ever-changing, context-dependent nature of work. Some tasks that are straightforward and routine, require fewer steps, or are less critical would be better formulated into a work instruction or checklist. Ultimately, any procedure or checklist should be designed in a way that encourages reporting and learning, rather than blaming individuals for errors.

Reviewing And Approving SOPs: A Collaborative Effort

The review process should include a cross-functional team comprising members from manufacturing, quality, engineering, and safety departments. Each team brings a unique perspective that can help identify potential issues that may not be apparent to others. The teams should understand what their role is in reviewing and approving the procedure, as each department will be viewing it through a different lens. For example, quality will be assessing instruction and flow, to ensure the process can be followed safely and meets the expectations of governing regulations. Engineering on the other hand, may be focused solely on the equipment and data expectations. Knowing their roles helps departments review the SOPs more quickly, reducing the time it takes to implement new procedures. In order to limit the number of times an SOP has to go back into revision, establish a mechanism for ongoing feedback even after the SOP is implemented, to capture any minor issues before they require a major revision. Use a robust version control system to track changes, making it easier to update the SOP as needed without starting from scratch.

For more complex and critical procedures, the cross-functional teams may want to conduct a risk assessment to identify the steps that are most susceptible to errors. Use tools like failure modes and effects analysis (FMEA) to evaluate the impact and likelihood of potential errors at each step. This also will improve the training associated with the procedure, as trainers will be able to home in on and emphasize where things can go wrong. In turn, the trainee’s brain is set up to understand what good looks like, as well as recognize when they are no longer maintaining positive control. In addition, performing a risk assessment aids in developing and implementing the right error-prevention tools for each task. For example, some procedures will span two or more shifts, requiring the hand-off of information and documentation. A good error-prevention tool in this case would be a shift handover report. This one- to two-page document can help drive a consistent delivery of outstanding tasks, such as samples that need to be taken or submitted, in progress hold times, and outstanding document review.

Training On SOPs: Beyond The Classroom

When it comes to technical procedures where manual manipulation and complex actions will need to be executed, training should not be limited to reading the SOP document. Two of the top eight error precursors under the category Individual Capabilities are “Lack of Knowledge” and “Indistinct Problem-Solving Skills.”3 This is why it is ideal to use scenario-based training to simulate real-world conditions, allowing operators to practice the tasks in an environment that is the same as or close to the same as the one in which they will be performing the tasks. There are a variety of options in the industry right now that use VR to allow trainees to try and fail in a simulated environment.

In a well-designed SOP training program, everyone has a similar, accurate mental model or structured understanding of knowledge about how something works or operates. This uniform understanding is crucial for consistent performance, quick error detection, and effective problem-solving. Therefore, training isn't just about teaching procedures; it's about aligning mental models across the team to ensure smooth, efficient, and safe operations. Such a well-rounded understanding can only be cultivated through hands-on experience and open communication, allowing trainees to raise questions and concerns. Successful training programs offer not only a basic grasp of these unique processes but also the underlying theory of the process, the design, and elements of the system, as well as its operational features.

Collaboration For Improved Oversight

Quality and manufacturing teams must have a symbiotic relationship, conducting joint audits to assess compliance with SOPs, as well as identify gaps in what the instruction states and how things are actually done. This collaborative approach ensures that both teams have a vested interest in the outcomes and can provide a more comprehensive view of performance.

SOPs are more than just documents; they are dynamic tools that can be optimized to drive down human error. Through the application of human performance theories and fostering collaboration between teams, organizations can create a more resilient system that minimizes errors. This not only improves the quality of the products but also enhances the safety and well-being of the operators who are instrumental in the manufacturing process. By taking a human-centric approach to SOP creation, review, and training, we can build systems that are not just robust but also adaptive, capable of evolving with our understanding of human behavior and performance. This is not just good practice; it's good business. After all, in our industry, the cost of human error can be immense, but the value of human performance is immeasurable.


  1. Dekker, S. (2013). The Field Guide to Understanding Human Error. Burlington: Ashgate Publishing Company.
  2. Thompson, H. a. (2013, May 3). Brain, Interrupted. Retrieved from The New York Times.
  3. U.S. Department of Energy. (2009, June). Standards. Retrieved from Office of Environment, Health, Safety, & Security:
  4. Wilson, L. (2023, April 27). Human Error is Not a Cause-It's a Consequence. Retrieved from Industrial Safety Review:,HUMAN%20ERROR%20IS%20NOT%20A%20CAUSE

About The Author:

Sarah Boynton is a consultant on the Quality Executive Partners (QxP) team. She has extensive experience in the biopharmaceutical/cell and gene therapy space, with a particular focus on cGMP training, human performance/error prevention, downstream processing, and non-conformance investigations. Prior to joining QxP, Boynton worked for Catalent Pharma Solutions, KBI Biopharma, AstraZeneca, Med Immune, and GlaxoSmithKline.

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