Where Poka-Yoke and Cybernetics Meet

Users ultimately determine the purpose of any device

Published: Monday, October 28, 2019 - 12:02

Today I’m looking at design from a cybernetics viewpoint. My inspirations come from cybernetics and design theorists Ross Ashby, Stafford Beer, Klaus Krippendorff, Paul Pangaro, and Ranulph Glanville. I was curious about how the interface of a device conveys the message to the user on how to interact with it. For example, if you see a button, you are invited to press it. In a similar vein, if you see a dial, you know to twist it. By looking at the ideas of cybernetics, I feel that we can expand on this further.

Ross Ashby, one of the pioneers of cybernetics, defined “variety” as the number of possible elements (or states) of a system. A stoplight, for example, generally has three states—red, green, and yellow. Additional states are possible, such as blinking red, no light, or simultaneous combinations of two or three lights. Of all the possible states identified, the stoplight is constrained to have only three states. If the stoplight is not able to regulate traffic acting in tandem with similar stoplights, traffic gets congested and results in a standstill. Thus, we can say that the stoplight was lacking the requisite variety.

Ashby’s Law of Requisite Variety states that only variety can destroy (i.e., absorb) variety. This means that the regulator should have enough variety to absorb any perturbations in order to truly manage a system. Unfortunately, external variety is always larger than internal variety. So the regulator must have the means to filter out unwanted external variety, and it should amplify internal variety to stay viable. An important concept to grasp here is that the number of distinguishable states (and thus variety) depends on the ability of the observer. In this regard, the variety of a system may be dependent on the observer.

With these concepts in mind, I will introduce two ideas (hypotheses) that I have been playing with:
1) Harish’s purpose hypothesis: The user determines the purpose or use of a device. The user is external to the design of a device. The user at any given point has more variety than the simple device. Thus, the user ultimately determines the purpose of a device. How many times have you used a simple screwdriver for other purposes than screwing or unscrewing a screw?
2) Counteraction hypothesis: When presented with a complex situation, the user generally seeks simplicity. When presented with a simple situation, the user generally seeks complexity.

The user has a tendency to move away from the perceived complexity of a device. If it is viewed as simple, the user will come up with complex ways to use it. If it is viewed as complex, the user will try to come up with simple ways to use the device. Complexity is in the eyes of the beholder. This can be also explained as upon realizing that something isn’t working, a rational being, instead of continuing on the same path, will try to do the opposite. 

A good example is a spreadsheet. In the hands of an expert, the spreadsheet can be used for highly complicated mathematical simulations with numerous macros; alternately, in the hands of a novice, the spreadsheet is just a table with some data points. In a similar way, if something is perceived as complex, the user will find a way to simplify the work to get the bare minimum output.

The cybernetic dance between designer and user

There is a dance between the designer and the user, and the medium of the dance is the interface of the device. The designer must anticipate the different ways the user can interface with the device and make the positive mannerisms attractive and the negative mannerisms unattractive. In cybernetics terms, the designer must amplify the desirable variety of the device so that the user is more likely to choose the correct way the device should be used. The designer also must attenuate the undesirable variety so that the user will not choose incorrect ways of use. If the design interface is providing a consistent message each time, then the entropy of the message is said to be zero. There is no change in the “message” conveyed by the design.

One of the concepts in lean is poka-yoke or error-proofing a device. From what we have seen so far, we can say that a successful poka-yoke device has the requisite variety. The message conveyed by the device is consistent, and the user always chooses the correct sequence of operation.

Krippendorff explains this nicely in terms of affordances of a device:
“When an interface works as expected, one can say with James Gibson (1979) that the artifact in question affords the construction that a user has of it; and when it does not work as expected, one can say that the artifact objects to being treated the way it is, without revealing why this is so.”

Krippendorff also explains that the interface does not carry a message from the designer to the user. This is an interesting concept. Krippendorff further explains that the user assigns the meaning from how the user interacts with the device. The challenge to the designer, then, is to understand the problem and determine the easiest way to solve it.

“Different people may interface rather differently with the same artifact,” wrote Krippendorff in 2006. “What is a screwdriver for one person, may be an ice pick, a lever to pry a can of paint open, and a way to bolt a door for another. Human-centered designers must realize that they interface with their artifacts in anticipation that the result of their interactions affords others to meaningfully interface with their design—without being able to tell them how.

“An interface consists of sequences of ideally meaningful interactions—actions followed by reactions followed by responses to these reactions and so on—leading to a desirable state. This circularity evidently is the same circularity that cybernetics theorizes, including what it converges to, what it brings forth. In human terms, the key to such interactions, such circularities, is their meaningfulness, the understanding of what one does in it, and toward which ends. Probably most important to human-centeredness is the axiom: Humans do not respond to the physical qualities of things but act on what they mean to them.”

Variety costs money

Another concept from the cybernetics viewpoint is that adding variety costs money. In theory, a perfect device could be designed, but this would not be practical from a cost standpoint. After all, a low price is one of the ways the designer can amplify variety. A good story that reflects this is the design of the simple USB. A USB cord is often cited as an example for poka-yoke: There is only way to insert it into the port.

When you think about it, a USB pin has two states for insertion, of which only one is correct. There is no immediate standard way that the user can tell how it can be inserted. Thus, the USB lacks the requisite variety, and it can lead to dissatisfaction from the user. The obvious question is why this isn’t an issue on a different connector, such as Apple’s lightning cord, which can be inserted either way. It turns out that the lack of variety for the USB is intentional. It was an effort to save money. A USB that can plug in correctly both ways would have required double the wires and circuits, which would have then doubled the cost. The Intel team led by Ajay Bhatt anticipated the user frustration and opted for a rectangular design and a 50–50 chance to plug it in correctly, vs. a round connector with less room for error.

Feedback must be instantaneous

Pangaro defines cybernetics as “having a goal and taking action to achieve that goal. Knowing whether you have reached your goal (or at least are getting closer to it) requires ‘feedback,’ a concept that was made rigorous by cybernetics.”

Thus, we can see that the device should be designed so that any error must be made visible to the user immediately, and the user can correct the error to proceed. Any delay in this can only add to the user’s confusion. The designer must take extreme care to reduce the user’s cognitive load when interfacing with the device. Paraphrasing Michael Jackson (not the singer) from a cybernetics standpoint, “The organization of the device should have the best possible model of the environment relevant to its purposes. The organization’s structure and information flows should reflect the nature of that environment so that the organization is responsive to it.”

Final words

I will finish with wise words from Krippendorff regarding how the user perceives meaning by interfacing with a device.

“Unlike what semiotics conceptualizes, from a cybernetic perspective, artifacts do not ‘carry’ meanings from designers to their users. They do not ‘contain’ messages or ‘represent’ meanings....

“For example, the meaning of a button is what pressing it sets in motion: ringing an alarm, saving a file, or starting a car. The meaning of a soccer ball is the role it plays in a game of soccer and especially what its players can do with it. The meaning of an architectural space is what it encourages its inhabitants to do in it, including how comfortable they feel. The meaning of a chair is the perceived ability to sit on it for a while, stand on it to reach something high up, keep books on it handy, for children to play house by covering it with a blanket, and staple several of them for storage. For its manufacturer, a chair is a product; for its distributor, a problem of getting it to a retailer; for a merchant it means profit; for its user, it may also be a conversation piece, an investment, a way to complete a furniture arrangement, an identity marker, and more.

“Typically, artifacts afford many meanings for different people, in different situations, at different times, and in the context of other artifacts. Although someone may consider one meaning more important than another, even by settling on a definition—like a chair in terms of affording sitting on it—it would be odd if an artifact could not afford its associated uses. One can define the meaning of any artifact as the set of anticipated uses as recognized by a particular individual or community of users. One can list these uses and empirically study whether this set is afforded by particular artifacts and how well. Taking the premise of second-order cybernetics seriously and applying the axioms of human-centeredness to designers and users alike calls on designers to conceive of their job not as designing particular products, but to design affordances for users to engage in the interfaces that are meaningful to them, the very interfaces that constitute these users’ conceptions of an artifact—for example, a chair, a building or a place of work.”

Always keep on learning....

First published Aug. 5, 2019, on Harish’s Notebook.

About The Author

Harish Jose

Harish Jose has more than seven years experience in the medical device field. He is a graduate of the University of Missouri-Rolla, where he obtained a master’s degree in manufacturing engineering and published two articles. Harish is an ASQ member with multiple ASQ certifications, including Quality Engineer, Six Sigma Black Belt, and Reliability Engineer. He is a subject-matter expert in lean, data science, database programming, and industrial experiments, and publishes frequently on his blog Harish’s Notebook.