Ambiguous Visual Controls: Caution! Possible Scalding


By Jon Miller |Post Date: October 10, 2014 6:34 PM

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Labeling and signage alone are about as effective in preventing accidents as fences are in preventing birds from flying over them. It sometimes seems that warning labels are only there to minimize the liability of the proprietors who were either too lazy, lacking in creativity or disengaged from their work to really think about how to prevent an injury, far from thinking how to maximize customer experience at every opportunity. Still, good clear visual controls can alert the conscientious user or operator to possible dangers.

This example of poorly designed and executed safety signage came to my attention only after failing to note or take heed of its warnings for three consecutive showers, and suffering the consequences. It reads:

注意! Caution!
ご利用の際、急にハンドルを回しますと熱湯が出る場合がございますのでご注意ください。 Please use caution as turning on the water, suddenly can result in unexpected extreme temperatures and possible scalding.


If it were not for my appreciation of ambiguous visual controls, I might have felt stupid or annoyed, rather than amused.

Why is this an ambiguous visual control? Let us list the ways.

Placement. The visual control is not at eye level.

Readability. The visual control is barely readable. The font is small. There are only words, no useful images. The droplets of water distort the letters, requiring one to look at it up close. The message is not concise. Here it is at near actual size.

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Punctuation. The punctuation, specifically the placement of the comma, makes the meaning ambiguous. It states, "...turning on the water, suddenly can..." which implies not that "turning suddenly" causes this, but that any turning will suddenly cause an unexpected and extreme change in water temperature. The latter scenario seems like a design defect in the plumbing hardware.

Translation. The translation is not precise. In fact the Japanese reads to mean "turning on the water suddenly" as in jerking the faucet one way or the other, can cause hotter or colder water than expected to come out. Or possibly, the original was in English, as the Japanese is much more muted, reading "Please be careful as turning the handle [knobs] suddenly can cause hot water to come out." No mention of extreme temperatures or scalding.

Caution. The instruction to "use caution" is inherently ambiguous. When avoiding mistakes or accidents, clear positive action is better than a clear negative or a vague action. Why not, "please turn the knob gently to avoid..."? At best, "use caution" is a vague action, as it is not clear where or how to exercise caution.

Choice. There are two knobs. To which does the warning label apply? One or both? The temperature of the shower was set using the lower dial, red for hot and blue for cold. This is a fairly common visual control. The knob worked as advertised. No sudden changes in temperature, the ambiguous and unnoticed warning label notwithstanding.

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Cartoons. The two cartoon stickers on the upper knob were useless. Both work the shower. It is not clear why the one on the left shows a person under what looks like a ceiling-mounted shower, and the one on the right a hand-held shower. There was no ceiling shower.

But here is the entertaining part. The water initially comes at the temperature set by the lower knob, regardless of which direction the upper knob was turned. However the upper shower knob was extremely sensitive. If turned even slightly beyond the exact center point for "off", the water briefly stops and then flows again. Unless one is wont to try out all directions of a knobs while showering, this is discovered only at the end of the shower, when turning it back in an attempt to find the "off" position. This results in the unfortunate customer experience of being doused in cold water at the end of an otherwise refreshing and pleasant shower. This was so counter-intuitive that it took me failed attempts over multiple days to understand that this was user error on my part, that there was very little margin of error between a safely concluded shower and a shock of cold water, and that the vague red blur three foot off the floor was an ambiguous visual control.

The hotel room had been recently renovated. We can speculate that the hardware was intended for dual ceiling and hand shower head operation. Since there was no ceiling shower, both directions on the upper knob released water to the only shower head. Only, cold water when unintentionally switching shower modes. Perhaps the cold water release was a "hot fix" to the scalding problem.

What's troubling is the journey made by this label in order to arrive at its ultimately ambiguous and futile home. The workers who installed the bathrooms and placed the labels there did not wonder at the location specifications, barely 3 feet off of the floor. It's understandable that they may not have read what was on the label. However someone had to compose, translate, typeset, design, approve, print, die cut and package this label. Nobody along that chain paused long enough at the word "scalding" being anywhere in the range of acceptable settings for a hotel bath, or to question such a label's efficacy and safety. User cautioned, job done.

One should not have to think so deeply or carefully when taking a shower in a hotel boasting more than 2 stars. But since it is so, let us be thankful for this bountiful lesson in various failure modes, from product design, installation, user interface through customer experience.

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