Last summer Rick worked at a shoe store where he was told there was a commission for selling more shoes so Rick worked really hard and sold many pairs. At the end of the first month, Rick's paycheck showed very little extra money on top of his base pay. So the following month Rick decided he was not going to work as hard because the commission from sales was such a tiny part of Rick's paycheck. Rick coasted through the rest of his summer job hardly sold any shoes. What motivational theory prompted Rick to do what he did?