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  • Writer's picturehidet77

Poka-Yoke


“Poka” originally comes from a bad play made during the game of Shogi (Japanese chess) or Igo.

There was a bad play made in a recent professional Shogi. But observing what happened when this bad play was made highlights the thinking behind a “Poka-yoke.”



“Yoke” means to avoid. “Poka” comes from “Bad play” in Shogi (Japanese chess) or Igo. Note that it is not “Illegal play” or “a hand played under a condition in which players are interrupted by someone else.” It would be an immediate loss if it is an illegal play, just like any board game worldwide. It is the same as not following standardized work; it must immediately be corrected. These board games are considered an unfair playing field when the player is interrupted or interfered with by non-players. Non-players must allow the players to focus on the game. Even under such conditions, mistakes are made. Those mistakes are called “Poka.”


There was a historic Shogi “Poka” on 2023/10/11, which resulted in Hujii becoming the first to hold eight major titles. This was game four of the Ouza title. Nagase was a four-time defending champion. And Hujii was the challenger. But Hujii had won seven out of eight major titles at that time. This game had enormous attention on whether Hujii will win all eight titles. Hujii was leading the series two to one before this game. Hujii was one win away from becoming history at age 21.

In the fourth game, Nagase was leading the game. Nagase was taking full advantage. The AI that calculates the winning percentage shows a 99% chance for Nagase to win right before this 123rd move. When Nagese made his 123rd move, the AI dropped the winning opportunity by 1%. It was clear that Nagase made a “Poka.” A few minutes later, in the quiet room where the game took place, Nagase was in apparent agony. He recognized his mistake. He was banging his head. Nobody said anything to him (Of course). And those media and analysts were panicking in a separate room. After a few minutes, Nagase surrendered. Hujii became the first to win and hold all eight major titles.


One thing to note here. I have NOT read a single article that described Nagase’s move as “Poka.” It is only mentioned as “Poka” in blogs (like here), tweets, or comments by senior Shogi professionals. Why? Because it is somewhat rude. Why do outsiders need to point out that the defending champion made a “Poka”? The defending champion recognized his mistake. He clearly explained what he was thinking then and how he got confused. He is in complete reflection mode. And if so, do others need to keep pounding on the mistake? And this is one aspect of “Poka.” It’s a mistake, but the owner admits it and reflects on it. It’s not about others telling the owner or blaming them. [And I sincerely apologize for describing that move as “Poka,” but it is a lesson I connected with “Poka-yoke.]


Additional historical facts. “Fool-proof” has originated outside Japan since 1900. “Fool-proof” is translated as “Baka-yoke.” Some people felt offended to be called “fool” (Which makes total sense.) Therefore, Singo started using “Poka-yoke” in the late fifties to early sixties. [In Taiichi Ohno’s Toyota Production System, it is called “Baka-yoke.”] Yet, when they changed the word, the meaning was slightly changed. In “Poka-yoke,” the operator must recognize mistakes like Shogi or Igo. It is not about somebody else, including a computer, telling someone it had made a mistake. It is about self-recognition of the error.


Poka-yoke is not fool-proof. We must understand these differences.


1. Environment

We should understand the environment where we can say it is a “Poka-yoke” environment. Like any board game, people should be allowed to focus on their work. They should not be interrupted or disturbed, especially during a cycle. There should be agreement among everybody in the organization to respect this simple rule. This was my first learning. When I went to the genba for the first time to do Kaizen, I was strictly told by my coaches not to stop the operator in the middle of the cycle. If I wanted to ask questions, wait, or talk to the team leader. This is the first step of respecting the people. We appreciate their focus on their work. If we interrupt, it looks like our purpose (even if it is to Kaizen) is more important than their work. Let them focus.


2. Standardized Work

The board games are complex. Shogi or Igo have so many ways to play. That’s why it is fun. People enjoy those games to enjoy the complexity. And that’s why it takes time. There could be hours to think about the next move. Because these professionals must think so much, they must eat lots of sugar during the game. Some Hujii manias follow what snack he had during the game.

Our work should be simple. It should not be designed for 500 professionals in the world. It should be prepared for ordinary people. And the guide to getting out of complexity is standardized work. The people should get a guide on the best method to accomplish the work. If the best way is not possible to complete in terms of quality and timing, the people should feel comfortable to pull the Andon to receive the help. They shouldn’t be dealing with the problems or figuring out the complexity.

As I mentioned, the Poka-yoke concept appeared around the sixties. Standardized work started in the forties. In other words, Poka-yoke was implemented on top of standardized work. Today, many companies operate without or by violating standardized work, but they have fool-proofs. Because they are trying to prevent errors in non-standard anything is possible conditions, the foolproof requires additional technology and cost. Poka-yoke is not.


3. Self-Reflection

Probably the most crucial part is the self-reflection aspect of “Poka-yoke.” It is not about someone else pointing out the errors. Or something else like the computer controlling the people. It is not like an operator assembles a product with puzzles; later, a computer tells them good or bad. During the assembly process, the operator should know if it did a good or bad job. When they make an error, they should be allowed to reflect on how that mistake happened. And they should be allowed to say that they made an error. Making an error is a normal thing for human beings. And participate in developing the “Poka-yoke.”


Please note that I am not saying we shouldn’t have “error-proofing.” I hate “fool-proofing” inside manufacturing. Most fool-proofing inside operations are designed even if the workers are not trained, violate standards, and are disturbed. You might need such devices in other working conditions, such as an airplane pilot. They are working in a situation where extreme problems might happen, risking the lives of passengers. Production should not have such extreme conditions. And “Poka-yoke” has somewhat more human touch compared to “error-proof.” It is not just about devices. The starting point was coming up with that device by reflecting on the mistake. And more people were involved in the creation of that device. They were given a chance to think about the error. It is not just the device but also the process of developing it.


Once again, I apologize for calling the Nagase’s 123rd move as “Poka.” But it made me think about “Poka-yoke."

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