Why I like my showers with two degrees of freedom

Imagine your basic shower — in a cabin or above a bath tub. The ones I’ve known for most of my life tend to have two knobs: one to adjust the flow of hot water, one to to do the same for cold water. Or else they have a lever you can pull and rotate: pulling increases the flow rate, rotating changes the temperature. The end result is the same: you can make your water flow more or less copiously, and you can make it hotter or colder.

This means our shower has two degrees of freedom: You can change two variables independently (within limits). Unfortunately, some hotels seem to consider this system too hard for their guests to comprehend and present the hapless traveller with a single, often strangely shaped knob. What it does if turned, twisted, pushed, pulled, shoved or glared at, the traveller hasn’t got the foggiest.[*] In most cases, what you get is the single-degree-of-freedom knob: the more you turn on the water, the warmer it gets. However, the problem is: you don’t know this yet.

Here is why I think this is a bad idea, from recent practical experience:

  1. You get ready for the shower, and identify the shower controls. One single knob, function unknown.
  2. You twist it experimentally, taking care to stay out of the reach of the shower head (or tap). Water comes out. Good.
  3. The water is cold. Well, that’s probably normal: let’s let it flow for a while.
  4. The water doesn’t get any warmer. So this is probably the cold water knob. You go in search of any hot water knobs, levers, buttons, pedals or other controls.
  5. After having finished your search of the shower area (naked), you decide the knob is all you have. Water is still cold. The only thing you can do is to turn it on a little more.
  6. The water is still cold. Or maybe a little bit more lukewarm? You twiddle the knob. Water splashes back and forth. Yeah, definitely getting a little more lukewarm.
  7. You carefully close off all shower curtains, take your heart in both hands, and give the knob a good strong twist. And wait a while.
  8. YAY, finally, warm water. You take your shower.

Dear hotel designers: Presenting tired travellers who’ve likely never been to your establishment with anything but a regular, clearly labled, two-degrees-of-freedom shower control knob system is not good user interface design.

[*] These things can get exceedingly complex — the worst I’ve ever had was in a swanky resort in Windsor I stayed at for a company function: the knob had red and blue dots in odd places, ridges and ratchets, could be turned a little, then pushed or pulled, and then turned in an entirely different way again… the frigging bath mat came with instructions for use, but I wasn’t the only one who’d stood naked, wondering at it for 10 min, before succeeding entirely by chance (or, as were, going unshowered).

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