Design Heuristics and Folk Wisdom

I've accepted the notion that one of the most influential sources behind the world's heuristics stems from folk wisdom. That is, direction from "They", as in "Feed a cold, starve a fever" or "Cure your hangover with a bowl of Menudo" where the true source is never really known or explained. And while folk wisdom is prevalent in my traditional, Mexican-Catholic home (which is indeed it's own, extraordinary brand of Catholic), I've always leaned towards trusting more reliable sources such as 1) evidence from testing/research and 2) experience from specialists.

Considering these sources, to what degree, if any, do we trust in folk wisdom for our designs? This great read from the authorities at UX Magazine offers some insight into the origin of heuristics and suggests that we are indeed relying on a lot of unknowns when it comes to UI/UX design.

The one example given for folk wisdom as a source for design heuristics in the aforementioned article sounded decent, but I'm not buying it. That may be because I've always worked with folks who push the notion of 'acting on data, not intuition' and verifying that data before doing things like making changes to process flows or adding UI elements to a page. Here's my advice to you, designer: No matter how talented you are, or what kind of formal training you've had make it a habit to be data driven in your design decisions. Get your hands around A/B testing, eye tracking and conducting focus groups and everything will be okay.