This is a working draft of a direct response to John Siracusa’s article about the Spacial Finder. This resource, on one of my all-time favorite tech sites ever (my forum login dates from 1999), has been used as the reference for many a spacial interface argument. I believe its an interesting article but fundamentally flawed in a couple ways.
John’s article on ARS has been used as the definitive guide to spatiality sense he wrote the darn thing over a year ago. To this day I believe that loyal ARS reading Gnome developers made the abrupt decision to ruin their UI, based almost entirely on that article.
The “Why Spatial?” section of his document attempts to argue the virtues of the Spacial Interface by providing 4 standards of usability. But a couple of the characteristics of his standard of usability are misidentified. For example:
Ease of learning: John says that the strongest characteristic of “ease of learning” comes from its adherence to physical laws, but this is obviously not the true. Swimming is something that totally adheres to physical laws, but I still had to take swimming lessons. Simplicity is what makes for “ease of learning.” Take a wall mounted type light switch for example. People who have never used one often misunderstand what it does and is for, but once they accidentally flick-the-switch; they understand its entire functionality and almost certainly never forget how to use it. They may not know what it DOES but they certainly understand how to use it. Its seem fairly obvious when you think about it, if you want something to be easy to learn; make it very simple to use. Let me give another example. Touch-less hand driers you find in U.S. bathrooms operate via motion sensors. They defy most everyday physical laws but once a person starts trying to mess with it, they very quickly figure out how to activate/use it. Again simplicity and not adherence to physical laws makes them easy to learn.
Memorability: The article goes on to say that door knobs and light switches do not move or change on their own, making their location and operation easy to remember.. This makes a lot of sense when you first hear it but the reality of memorability is much simpler. Consistency is the key here. My best friends house has all of the light switches at hip level. They did this because they wanted the light switches to be reachable by their children when they were very young. I spent years of my life in that house but I never got used to the location of the switches. Even after I got used to reaching DOWN for the switches I would still miss the switch (on the first try) because it was such a non-consistent movement when compared to every other house I had ever been it. Not only does consistency aid in memorability but it allows you to easily transfer knowledge from one learned experience to another. To take the light switch analogy again; once a person learns how to work a light switch they can work almost an light switch they will ever run into. Just as long as those light switches are fairly similar to the one they learned on. Consistency is what makes for memorability and can be achieve in many more important ways than simply physical location.
Efficiency and Satisfaction are both admirable goals of usability but are not specific traits to the realm of spatiality. In fact simplicity and consistency are not specific to the realm of spatiality. Simplicity and consistency are traits pursued in mathematics, science, engineering, philosophy, and even religion. Usability then gets advanced by following universal rules of understanding instead of some limiting subset of spacial rules. Again, this makes a great deal of sense when you consider it. Things will be most usable if they follow rules (or models if you like) that already fit into the way we are designed to do things. This is very similar to what John Spatiality is part of those rules