Therefore over time your brain will learn the mental model applied by the engineers — (not the designers!) — to get it right every time. However I’m guessing you use your mother’s stoveless often. So you have the issue of short term vs long term recall. With your own stove your learning is re-inforced almost every day I would guess, so that learning you did when you first moved into your place or when you bought the stove becomes habit. With your mother’s stove, you don’t get that luxury. So it’s harder.

As a designer, how do I know if my unconscious assumptions about relatedness are universal?

Well, I’m guessing that you don’t need me to tell you this, but, whatever… You’ll want to regularly climb inside the minds of the people who use your stuff by using user centred design tools like ethnographic research, personas, usability testing and crucially, iterative prototyping.

How can I discover and/or predict which assumptions will cause usability trouble in the real world?

You use iterative prototyping and usability testing. You put stuff out there for people to use and get feedback to build into the next version. Simple as that!

Enjoying your site… (but unfortunately not the Captcha spam doohicky)

Regards
DJ