The real reason milk is hidden at the back of supermarkets and stores play relaxing music has been revealed. It's all part of getting people to spend more, according to UNSW marketing professor Nikita Garg. "Their purpose is to sell more, that's their job, they are storing lots of goods. They want you to buy more than what you have on your list," she said. The tactics are based on consumer psychology to trigger reminder or impulse purchases, so people coming to the store for one thing end up leaving with a full basket, Professor Garg said. A key tactic to watch for is 'locked-in deals' - usually with a bright red label indicating a capped price. Professor Garg said this was often the same as the original price of the item and misled shoppers into thinking that they were saving money. Deals that offered 'buy two, get one free' could also catch out shoppers and might not be cost-effective at all, she said. Even the layout of the store was designed to put staples like milk and bread far from each other and usually at the back. IN OTHER NEWS: That ploy had shoppers walk through and spend more time in store, Professor Garg said. Calming music is strategically played through the supermarket to encourage shoppers to linger longer. Bigger shopping carts were also used to cajole shoppers to spend more as people think they've forgotten or are missing some items. With the price of food rising by 7.5 per cent in the past financial year, Professor Garg said the cost of living had led to shoppers becoming more aware of price movements. Her tip to saving and getting the best deals was to shop at different stores. "You could go to one shop to get your meat and then another to get your veggies because you as a consumer have taken the time to research and know where the best and cheapest products are," she said.