In the spirit of taking usability analysis to everyday object. I’ve long decided to do a blog post on show knobs. The designs of shower knobs are very versatile. They have all different shapes thus provide different affordances. But for the most of time, the affordances aren’t very clear. A shower knob can afford twisting, pushing, or pulling. Things become really confusing, when the design requires not only one but two or three of these action together to work. Just by the look of them, you can never tell how it works. This inconsistency across different design of shower knobs has resulted people forming multiple mental models in their head. They are forced to experiment with it, and figure out which mental model fits the product. Here are some examples of confusing examples of shower knobs.
This design is very common. The knob clearly indicates that you need to twist it. What’s problematic is the red and blue stickers. The picture shows one of many examples. The problem with this example is it implicates that you can’t adjust the temperature of the water , that you can either go “hot” or “cold”, where in reality you may be able to adjust the temperature by twisting it to different degrees. Another example is putting in a gradient red to blue semi-circle sticker, or two semi circles with the gradient of red on one side and blue on the other side, to the chrome plate behind the knob. The problem with this method is that, since there is no arrow pointing on the knob, you can never tell what level of temperature you are right now. The worst design of this kind is to add push pull feature to the knob, it’s complete madness. I won’t even go that far.
Another popular design of shower knob is this handle shape knob. The handle shape indicated you can pull it. And the handle pointing to the red and blue sticker on the chrome plate will also indicate the temperature of the water. However there is difference among designs on the limits of twisting. Some designs allow you to go from horizontal left to right, where neutral sits between. Some designs allow you go go from vertical down to up, or the other way around. This gets very confusing sometime, if you get used to one of these and expect all shower knobs to work that way. The worst case with this is that you can’t pull the handle, which is completely contrary to its affordance. The shower knob in my apartment right now is like this, so it took me a lot of time to get used to.
You may want to ask why I’m super interested in shower knobs. This is because people tend to feel insecure, and sometimes cold when they are naked in the shower. You just want that hot water to run down from the shower head as soon as possible. When that doesn’t happen because you can’t figure out how the knob works, it gets more annoying than something on your computer stops working.