Five suggestions for augmenting Six Sigma with human-centered design principles.

My first-ever introduction to Six Sigma was during a visit to a Triumph facility in Dallas, TX.

I was working for a company that helps manufacturers create actionable plans based on the data collected by ERP (enterprise resource planning) systems such as those made by SAP.

As part of our engagement, we were meeting with the team of stakeholders tasked with monitoring the health of Six Sigma initiatives. One woman introduced herself in a way I’ll never forget (name and title changed):

Hello, my name is Susan. I’m senior manager and a Six Sigma Black Belt.

I was impressed. Both with her pitch (what a badass) — and that a system like Six Sigma could become such a cornerstone of operations that people included it in their introduction. Motorola alone has claimed that Six Sigma has saved their company over $17B since they’ve implemented the system in the early 90's.

And yet, for all its glory, Six Sigma appears to be focused “within the walls.” It’s a tactical, effective process nonetheless geared explicitly towards physical processes and spaces. This inherent bias is an opportunity—companies can take the structure of Six Sigma and direct it in new and interesting ways—and add a significant amount of value.

Six Sigma has saved Motorola upwards of $17B

Let’s expand the scope of Six Sigma. In the 25 years since companies adopted Six Sigma, the world spun and humanity came up with a multitude of new ways to improve the way in which we work. Innovations in software, our understanding of human psychology, and human resourcing best practices have undergone drastic changes . These changes and innovations in organizational process and culture all represent opportunities to add immense value.

There’s plenty of new experiments to run along side what is already working.

Here are five strategies to help guide Six Sigma projects, get outside “the box”, and produce high value.

Logistical organizations can further improve their operations by adopting five human-centered innovations. These are areas that not explicitly addressed in the Six Sigma doctrine, to my knowledge.

  • Promote a healthy culture—make it inclusive, honest, and safe for everyone
  • Make interfaces human-centered and easy to use
  • Incorporate “desire paths” into formal processes
  • Understand the absolute power human physiology
  • Map your entire system—don’t stop at the edge of the factory floor

Promote a healthy culture.

Culture is a critical component of creating an efficient, high-functioning company. That’s why it’s first on my list. Since this claim is met with skepticism in many quarters, let’s consider a case study of poor cultures in hospitals:

Hospitals that have dysfunctional cultures—where nurses are afraid to call out errors on the part of surgeons—have significantly worse outcomes for patients, according to a 2008 study by the Joint Commission. This leads to extreme human trauma—deaths, injuries, lawsuits, and psychological damage.

If employees feel that they cannot point out errors when they see them, then major errors and defects are more likely to occur and may go unresolved. This is problem not of process, organization or hierarchy — but of culture.

What does it mean to have a good culture? Whole books have been written about this (I recommend Laszlo Bock’s Work Rules). At a basic level, a “good” culture is one where employees feel free to have an open and honest discussion about issues, without fear of retaliation.

Make ALL your interfaces human-centered.

Companies need to recognize that every interface is there for use by a human—and a potential source of error in the manufacturing and sourcing process. Borrowing from Six Sigma, we want every part of the process to be as efficient as possible. That means not letting opportunities for improvement slip by.

An example of a complex SAP interface. Even modern-looking UIs can have user experience issues—there’s ROI to be gained from designing systems that cater to users (rather than the other way around).

Whether an interface is used by employees, vendors or customers, we must recognize that all interfaces are inputs. Poorly-designed inputs will increase error rates and will continue to do so, day-in and day-out until they are fixed.

A poor interface is not just a one-time cost, it’s an ongoing drag on the efficiency of the entire system.

Incorporate “desire paths” into your formal processes.

A desire path is a “…path created as a consequence of erosion caused by human or animal foot-fall traffic. The path usually represents the shortest or most easily navigated route between an origin and destination.


An example of a desire path (i.e. shortcut)

Let’s face it—people are lazy. Another way of saying this is that they try and produce the largest value for the least amount of input. Another way of saying this is that they are efficient.

Many employers fight desire paths, categorizing them as inefficiency, waste or laziness. In many cases, this is a correct assessment. For example, we sometimes wear gloves when performing a task—we give up optimal efficiency in order to protect our hands from harm.

Oftentimes, desire paths can lead to great insights into efficient modes of work. Just look at the following example from Michigan State University:

Michigan State University has incorporated desire paths into their formalized walking paths across their campus.

MSU incorporated these “desire paths” into their landscaping and walking path architecture. The result might be messy from an aerial view, but it’s also a picture of organic efficiency. Each individual’s selfish desire to move efficiently through the grounds gives rise to paths that can be used by everyone to travel in a highly efficient way. If each of MSU’s 39,090 students saved 1 minute each day over the course of 180 school days, then MSU’s desire paths will have saved students ~100,000 hours of travel time in a single school year.

That’s the beautiful thing about scale. Small improvements to a large system add up.

Recognize that human psychology and physiology plays a huge role in human behavior—and therefore in the manufacturing process.

Humans are amazing animals. But we’re still just that — animals. We have brains with huge energy and nutritional needs — needs which do not always square nicely with regimented production schedules and staffing requirements. Think of the term ‘hangry.’ If you’re familiar with this concept, then you might be amenable to the idea that our behavior is subject to many small and seemingly trivial variables. These include glucose (sugar) intake, previous episodes requiring concentration, minor sleep deprivation and more.

If this idea seems unimportant, then consider the following study by the National Academy of Sciences:

A judge’s hunger and fatigue largely determines a prisoner’s fate when considering parole applications

A disturbing demonstration of depletion effects in judgment was recently reported in the Proceedings of the National Academy of Sciences. The unwitting participants in the study were eight parole judges in Israel. They spend entire days reviewing applications for parole. The cases are presented in random order, and the judges spend little time on each one, an average of 6 minutes. (The default decision is denial of parole; only 35% of requests are approved. The exact time of each decision is recorded, and the times of the judges’ three food breaks–morning break, lunch, and afternoon break–during the day are recorded as well.) The authors of the study plotted the proportion of approved requests against the time since the last food break. The proportion spikes after each meal, when about 65% of requests are granted. During the two hours or so until the judges’ next feeding, the approval rate drops steadily, to about zero just before the meal. As you might expect, this is an unwelcome result and the authors carefully checked many alternative explanations.

-From Thinking Fast and Slow, by Daniel Kahneman

Chart showing favorable decisions on the y axis based on time of day and proximity to meal and break times (x-axis). You can’t make this stuff up. (National Academy of Sciences website)

In your own company:
Are accidents occurring with higher regularity just before lunch or breaks? What are the error rates of part orders entered just before meals? These are just a few of the questions companies could pursue.

Map your entire system—don’t stop at the edge of the factory floor.

Six Sigma’s bias towards physical space may discourage practitioners from thinking past the walls of the production facility. Modern production, especially at large scale, extends well into the digital world. It also extends into more ephemeral deliveries of service or singular customer touch points (like a phone call). Consider everyone involved, from 3rd-party vendors and suppliers, accounting, to customers, employees, stakeholders and more.

Map all inputs so you have a visual representation of how information, supplies, people and processes flow through a given system.

An example of a service map for customer touch points across time. This kind of map can be expanded greatly to show complex organizations and workflows. Courtesy of Adaptive Path.

Visuals like the above are more easily processed by the human brain. Humans evolved highly sophisticated linkages between knowledge and visual processing. The old cliché—”a picture is worth 1,000 words”—is true. It’s a result of millions of years of evolution in an environment rife with predators and threats. Let’s use that bit of human evolutionary physiology to our advantage.

A map of your entire system will help the team see a complex system from a high-level vantage. Like a general scouting the battle field, you’ll be able to see spots where errors are more likely, or see inefficiencies at play. A good map will enable better discussions and speed agreement about proposed solutions.

I love Six Sigma’s focus on structure and measurement. To that mix I would add some human-centered design thinking. In that way, service and logistics-delivery companies can continue to enjoy the huge improvements in efficiency that Six Sigma ushered in during the 1990’s and beyond.

If you liked this article, please like, share or comment below. I will incorporate helpful feedback into the text of this article.



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Jon Simmons

Jon Simmons

Product Design Director | SXSW speaker | Top-rated instructor at General Assembly