Motion detection and common knowledge

I have just read Sugarenia’s The problem with motion detection post:

Now let’s take the other example, one of my favourites: let’s say you have a tap with motion detection. You see it, see no visible way of controling it, no stickers around. You try turning it (I know I’ve done that many times) but it won’t work. You look for buttons on the wall or on the floor, ’cause hey, you’ve seen that around, but there are none. No visible way of controlling a tap. What would you do? I’ve left. Many times.

I have also been stressed (you are stressed when you are not in control) by similar systems, more than once. Indeed, the last thing to try was placing my hands under the tap, but I somehow managed to find how it works. I am sure there are many people who quit trying, or learned by chance how it works by seeing or asking someone who knew how to use the tap.

Now, the designer of the tap wanted to give some attributes to it and in order to do that, he had to forget about the user model. The user model is how someone expects something else to work. For example, we are all trained to use many different types of taps. Most of them are based on the same pattern: In order to start them you have to look around for some kind of a start/stop mechanism. You should either move a stick or turn a valve. Even with some automatic taps, you still get a start button or something, and we all know that a button should be pressed.

The problem with the motion detection method of starting a tap (placing your hands under the tap) is that it is way off the user model.

According to Joel Spolsky in User Interface Design for Programmers, when it comes to designing the UI, one should try to be as close to the user’s model as possible if he wants his UI design to be intuitive and as a result successful.

Although the aforementioned book is for designing software, the advice can be applied to almost anything that needs to be designed and needs to interact with humans.

I have a question though. How is the user model created in our heads? I am sure people in 1800 didn’t have the slightest idea about how a proper UI for an MP3 player should have been designed, but I am sure they knew what was the best design for a sword and people knew where to hold it from because the design was intuitive to them.

Even with a sword, of course, people needed to be trained about its basic usage at least once in their life. The fact that you should hold a sword from a specific point instead of the blade, can be difficult to understand for someone that has never seen a sword in his life.

If you have children, try to remember the first time you had to explain the usage of a knife and how they should protect themselves because of how the knife can cut you if you are not careful. Also, remember how a child that sees a knife for the first time, might hold it from the blade because the child doesn’t know what the knife does.

We can argue that the user model is what most people are used to and what is a common knowledge. Everyone knows how a tap works. We are trained from a small age to operate one.

In software, we all know how a button looks like and we all know that we can push it. He have learned through experience what are the general characteristics of a button. Although you can have dozens of styles the main characteristics of a button are the same across all styles, and these make you want to push it.

What happens when the designer wants to innovate and improve things, but the design breaks the user model? Shouldn’t designers try to improve things? How can using a tap with motion detection be intuitive? Can it be done without putting signs with instructions?

One way is by just throwing it at users and let it become common knowledge. After a while it will become common knowledge.

In order to make this period smaller, one could try to think something clever that connects the old user model with the new way of using the tap. For example, the designer can place a fake turning handle under the tap so that the user would try to turn it and in the process would place his hands under the tap. I am sure there might be more elegant ways of tricking the user to place his hands under the tap.

What do you think? Do intuitive designs genuinely exist or do they exist because of the common knowledge that starts to pile up?

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