Fast-food menus are among the most rigorously tested products of our consumer culture. Because the decision of what to order for lunch isn't that important in the grand scheme of things, we don't spend much time or thought on it. Instead, we rely on subtle cues in the environment. Say your friend mentioned having a barbecue sandwich yesterday. The odds are, you're more likely to try a McRib sandwich today (assuming you like barbecue, and the friend). Memories are short, so the most powerful source of cues is the menu. Chains know that and spend a lot of effort on their menus. In many cases, menus and prices are intended to nudge consumers into ordering more than they might have otherwise.
• The Starbucks menu uses the "rule of three." The menu offers three sizes of coffees, given the enigmatic names of Tall, Grande, and Venti. (They're 12, 16, and 20 ounces respectively; 24 ounces for cold Venti drinks, to allow for ice.) Since Starbucks newbies won't know what they're getting, they tend to order the middle choice, Grande. In the psychology literature, this is known as "extremeness aversion" — people instinctively favor a middle choice, figuring it's safer. Guess what? You've just ordered two cups of expensive coffee. The Grande's sixteen ounces is two regular cups. Here's a secret: Manys Starbucks will serve you eight ounces of coffee, but you have to ask for a "Short" coffee (which isn't listed on the menu). You do have to remember that password "Short," though: Company policy says that a customer who asks for a "small" coffee is to be given a "Tall" one.

Really interesting article about the pscychology of Starbucks' menu... Enjoy!