 First psychological hack is the decoy effect. Starbucks mainly offers three sizes for the drinks. Tall, grande, venti, and this is not by accident. They strategically have three different sizes because having two is very easy to compare side to side to get the best bang for your buck. Whereas when we include a third option, it becomes very difficult for us to compare the three. This psychological feeling pushes us to actually make the decision on what we think is the most advantageous rather than what we need. Because you, just by spending an extra dollar, you get double the amount of coffee, which seems like a really great deal. That's reason why every time you go into Starbucks, they always ask you, grande?