“Human Errors, Poka Yoke are concepts brought to life from my experience with coffee cup. One can learn a lot about Poka Yoke and Human Errors. This is a story about what a coffee cup taught me about how poor design in our products and systems invite human error.
Many years ago, I had to travel to Dublin every few months for work. […] One very early morning while waiting for the taxi to pick me up at my hotel to take us to the airport, my colleague with whom I was traveling with at the time had ordered coffee while I ordered a Coke since I’m not a coffee drinker. They brought him his coffee in this cup.”
With its unsightly bumps and nooks, the “fancy cup” you show is not even pretty, which makes you wonder what the designer had in mind. The issues you bring up, however, are more about usability engineering in Don Norman’s sense, than Poka-Yoke.
A properly designed handle is self-explanatory in that any user who has never seen a cup will immediately understand what it is for. But it doesn’t make the cup mistake-proof: there is nothing physically preventing you from pouring coffee onto it while it is upside down.
Usability engineering is about controls that look and feel distinctive to the touch — as opposed to rows of identical buttons — that give you feedback when you have activated them, that have shapes that naturally lead you to use them properly, that respect cultural constraints in the meaning of shapes and colors, etc.
Applying these principles in designing human interfaces reduces training costs and the risk of errors. It is valuable, but it does not prevent errors.
Incidentally, why do so many cultures, including Japan and China, use cups with no handles? An alternative to handles to avoid burning your fingers is the double-walled cup, and I have seen some from China. Otherwise, I have resorted to the Arab way of holding a handleless tea cup: between my thumb on the bottom and my index finger on the rim.
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