The supermarket is designed to lure customers into spending as much time as possible within its doors. The reason for this is simple:The longer you stay in the store, the more stuff you&39;ll see, and the more stuff you see, the more you&39;ll buy. And supermarkets contain a lot of stuff. The average supermarket, according to the Food Marketing Institute, carries some 44,00 different items, and many carry tens of thousands more. The sheer volume of available choice is enough to send shoppers into a state of information overload. According to brain-scan experiments, the demands of so much decision-making quickly become too much for us. After about 40 minutes of shopping, most people stop struggling to be rationally selective, and instead begin shopping emotionally - which is the point at which we accumulate the 50 percent of stuff in our cart that we never intended buying.