They did an experiment where they gave some customers a ‘buy ten get one free’ card, while others got a ‘buy twelve get one free card’ but with the first two stamps already filled in. In practical terms, the loyalty scheme was identical, but the customers bought coffees more quickly to full up the ‘buy twelve’ cards in less time – in line with ‘goal gradient hypothesis’ – despite the fact that the actual progress towards the goal was no different. The researchers call this the ‘illusory goal progress’ effect and shows that our perception of how close we are to achieving something can be easily manipulated by shifting the goal posts. (via What motivates us more than most anything else? - Barking up the wrong tree)