I've always called this collection of phenomena thermostat fallacies, but my dad does HVAC for a living, so, go figure. I'm not even sure that they are proper fallacies.
The premise
In our cars, the analog dial or lever spanning a blue triangle stacked on a red triangle presents an analog blend of temperatures. At least that's how they used to work. But in analog home thermostats, and increasingly in cars, in multiple zones even, the temperature dial offers "now" and "target" temperatures.
This can confuse the crap out of people.
Anyway, in the car, with the old fashioned thermostat, most of us start out with the dial cranked to all hot or all cold and then adjust to comfort. Being uncomfortable is uncomfortable, we seek its undoing with a vengeance. We don't want the inside of the car to be 85°F in February, we just want it to be 68°, or whatever, faster than if we asked the car vents to spit out 68° degree air.
But home thermostats don't work that way, and not letting that stop the mind from thinking that they do is what I call the thermostat fallacy. It has three faces. I'll present them here as design patterns.
Do not try to put significant figures into an binary bucket
For example: Coming home cold, and raking the analog home thermostat dial up to 85°. If the house is already 64°, setting the thermostat target to 70° or setting the thermostat target to 85° make no difference whatsoever. That's just how the things work. 85° doesn't fit into the on/off bucket, it fits into stop when bucket. The heating and air conditioning is not working harder, it's just running longer, and will eventually boil the frog.
Do not represent a binary state with exclusively insignificant figures
This is the inverse of standard thermostat fallacy and better demonstrated in other technologies.
For example: Nearly every instance of numbered badges of unread email, unread RSS and atom subscription articles, unread twitter posts, unread whatever are representing "you have unread items" with "you have a specific-yet-useless number of unread items."
You see, if the badge says 43 now, and five minutes later, it says 44, it still only conveys "There is unread email". The number lacks context but it still has to be parsed. More importantly, there is no unit-comparability. All of those messages could be spam, or one could be a life changing job offer, and so on.
Do not expect insignificant figures to have unit-comparibility
For example: Insisting thermostats at separate houses set at the same temperature are creating the same environment in spite of perceived differences in temperatures caused by room layout, thermostat placement, humidity, elevation, and so on.
This is a big one. I consider it an instance of ceteris paribus, or the all else equal fallacy. It's what leads people to wonder why Oscar the Grouch doesn't just go to college and get a job, damnit.
So?
Significant figures matter, but when human perception is the target, and not scientific measuring apparatus — lossy compression isn't just okay, it's humane. The mind works better in some cases with fuzzy numbers than specifics. When numbers can't be avoided, keep the thermostat fallacies in mind when working with them.
