I had occasion to go through a Starbucks drive-through earlier this week, and of course it raised some interesting design points. Starbucks always does, right?
First, the drive-through line itself was interestingly placed. If you were standing in the road, looking at the building, the drive-through window was on the right side. This means that cars don't have a ton of room to line up -- my commuting partner said that she's even seen the cars backed out into the road before. The design solution is pretty simple; just put the window on the other side of the building, so the cars can wrap all the way around the building.
Next came the ordering itself. My traveling companion ordered a breakfast sandwich with just egg and cheese, but the cashier read back the order as a "sausage with no sausage." In interaction design, we always preach that the designer shouldn't let the implementation model take over for the user's mental model, and this is a prime example of that phenomenon. The implementation model is how the Starbucks employee thinks of the sandwich: she refers to the sandwich in its entirety as "a sausage" and then qualifies it as "no sausage," but the user described it by listing the ingredients remaining after the sausage was removed. In this case, it's best to just go with the user's mental model -- but that's not how Starbucks rolls!
This reminds me of some problems I had with a Taco Bell back in my high school days in St. Louis. I'd want to order items sans beans, but I'd always describe them by listing the ingredients I did want... and of course, I'd always get a messed-up order. One day, I looked at the receipt and realized the cashiers didn't enter in the items by what
did go on them (my mental model) -- rather, they keyed in what was
removed from the default recipe. Once I figured this out, I started ordering "backwards," and I started getting correct tacos (apparently I was quite the junior interaction designer, haha).
Going back to Starbucks, there is one possible defense for their rewording of the order. It could be that they're encouraging patrons to learn the Starbucks-specific jargon that allows membership into its coffee elite. I've always been a bit impressed by the way Starbucks has leveraged design methods to create an "in-crowd" atmosphere among its expert users (even if it does come at the cost of learnability), so perhaps this is a subtle aid for newer customers to help learn the language.
In interaction design, we talk about something called a "pedagogic vector." This sounds complicated, but all it really means is that when designers have some function they want the user to learn, they attach it to a simpler function they know the user will perform. This forces an association between the two functions and helps the user expand their mental model of how the system works. A good computer example of this is keyboard shortcuts in menus: When a user sees "
Save" enough times and sees the "Ctrl + S" across from it, he starts making an association, and it once he tries it out and discovers the shortcut, he learns what the underlined letter means.
In Starbucks' case, it's possible that restating the order pairs the "correct" phrasing with the novice user's naive phrasing to create a pedagogic vector that helps the user learn the jargon. Of course, it's also possible that the Starbucks cashiers are just snotty. I guess it depends on what kind of motives you want to ascribe to them. :)