Slot machines account for about 85% of the profits at casinos. Think about that for a second. A massive industry has been built by getting you to feed cash into a finely tuned machine that is specifically designed to take cash from people. That’s a trick worth understanding. From Brad Plumer in Vox: How casinos get you to spend more money.

+ If you’re going to let a machine trick you into spending more money, you might as well use the technology that is getting you to tip more. This is the ultimate example of the power of a good user interface.