—— If you missed the first part of this article, you can find it here: 1. Design Theory ——
In Part 1 of this article, I established that when a starting motion has a causal relationship with an end motion, our mental model expects the motions to match.
Thus, in a user-focused, intuitively designed door lock, the direction the key turns should match the direction the deadbolt moves (i.e., turning the key away from the strike plate opens the door, while turning it towards the strike plate locks the door).
The caveat to any intelligent design is a pesky little phenomenon called Jakob’s Law. For those unfamiliar with the term, Jakob’s law posits that people will transfer expectations they have built around one familiar product, to a similar one.
That means that if you’re used to using a product with a certain design - even if that design is bad - whenever you approach a similar product, your mental model for that class of products is such that you expect it to behave in the same way.
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That’s why in UX, it is largely discouraged to break the mold or reinvent the wheel - for example to use unusual icons for navbars. Or why rebrands or redesign are so often not initially accepted by users - even if they’re objectively better, people don’t like adjusting to new systems.
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Why am I bringing this up in an article about door locks?
I always knew, when talking about the design of door locks, that there would be one major issue: anyone who has spent 18 years locking and unlocking the same door will be accustomed to the way that door opens, and expect all other doors to open that way, regardless of if the design makes sense to the brain or not.
So, in the world of door locks, we have a “best-practice” key-turning direction - but what if a particular user is accustomed to doors that open by turning the key the opposite way? Let’s see this play out in real life.
Knowing some of you wouldn’t be convinced by my infallible logic, I conducted some totally-solid-WhatsApp-based User Research.
I sent 11 contacts a high fidelity (😉) drawing of a left-opening door and I asked “which way would the key turn to open the door?”
Astonishingly I got a 100% response for “clockwise.” Excellent! Hypothesis supported, clearly!