I’ve run across this interface design issue twice in the recent past, and it confused me both times. I took my camera back to the gas station the third time, just to document the interface behavior. How’s that for following through?
So I was at the Shell station this weekend, filling up my tank (Fig. 1). I finished filling up, returned the nozzle to the pump, and approached the screen to finish my transaction. The first question on the screen was “Would you like a car wash?” There were “Yes” and “No” options onscreen, and each was tied to a grey button off to the side of the screen—much like an ATM interface (Fig. 2). “No” was attached to the third button down on the left, and “Yes” was tied to the fourth button down on the left. I pressed “No” to answer the car wash question. The next question was “Reciept?” I made sure to pay attention to the order of the answers, because this is where I remember it got tricky. My attention paid off because, sure enough, the “Yes” and “No” options switched positions (Fig. 3)!
What’s the deal there? Did they do some extensive user research and find that customers who categorically select “No” for car wash select “Yes” for receipt? Or that customers who always select “Yes” for car wash never want a receipt? Were they trying to save me the trouble of moving my finger half an inch to select “Yes” for my receipt?
It’s not a good idea to change an interface protocol once it’s been established. Deviations from expected behavior confuse the flow of the experience, even on something as basic as a gas pump.